Effects of varenicline on abstinence and smoking reward following a programmed lapse

Varenicline for smoking cessation in individuals who smoke cigarettes and use electronic cigarettes: a double-blind, randomised, placebo-controlled phase 3 trial

Background

The efficacy and safety of varenicline for smoking cessation among individuals who smoke tobacco cigarettes and also use electronic cigarettes (known e-cigarettes or vapes) have not been studied. We aimed to address this knowledge gap and examine predictors for smoking abstinence.

Methods

In this double-blind, placebo-controlled, single-centre randomised trial in Italy, we enrolled adults who had used an e-cigarette daily for at least 12 months and who also smoked at least one tobacco cigarette per day and had a willingness to quit smoking. 155 participants were randomly assigned to receive either varenicline (n = 78) or matched placebo (n = 77). Varenicline (1 mg, administered twice daily for 12 weeks) was given in combination with smoking cessation counseling in dual users with an intention to quit smoking. Participants in both treatment groups received the same smoking cessation counselling throughout the whole duration of the study. The trial consisted of a 12-week treatment phase followed by a 12-week follow-up. The primary efficacy endpoint was continuous abstinence rate (CAR) in weeks 4-12. Secondary efficacy endpoints were the CAR in weeks 4-24 and 7-day point prevalence of smoking abstinence at weeks 12 and 24. This study is registered in EUDRACT, 2016-000339-42.

Findings

Between November 2018, and February 2020, 114 participants (61 in the varenicline group and 53 in the placebo group) completed the intervention phase at week 12 and 88 participants (52 in the varenicline group and 36 in the placebo group) completed the follow-up phase at week 24. CARs were significantly higher for the varenicline vs placebo at each time-point: 50.0% vs 16.9% (OR = 4.9; 95% CI, 2.3-10.4; P < 0.0001) between weeks 4 and 12; and 48.7% vs 14.3% (OR = 5.7; 95% CI, 2.6-12.3; P < 0.0001) between weeks 4 and 24. The 7-day point prevalence of smoking abstinence was also higher for the varenicline than placebo at each time point. Adverse events were rated as mild or moderate and rarely led to treatment discontinuation.

Interpretation

Our findings indicate that inclusion of varenicline in a cessation programme for adults who smoke and use e-cigarettes with an intention to quit smoking could result in smoking abstinence without serious adverse events. In the absence of evidence from other smoking cessation methods, it could be useful to suggest the use of varenicline in cessation programmes specifically designed to help dual users stop smoking. Further research in larger and more generalisable populations is required to strengthen such a suggestion.

Funding

Global Research Award for Nicotine Dependence, an independently reviewed competitive grants programmeme funded by Pfizer.

Efficacy and safety of combination behavioral activation for smoking cessation and varenicline for treating tobacco dependence among individuals with current or past major depressive disorder: A 2 × 2 factorial, randomized, placebo-controlled trial

BACKGROUND AND AIMS

Treatment of depression-related psychological factors related to smoking behavior may improve rates of cessation among adults with major depressive disorder (MDD). This study measured the efficacy and safety of 12 weeks of behavioral activation for smoking cessation (BASC), varenicline and their combination.

DESIGN, SETTING, PARTICIPANTS

This study used a randomized, placebo-controlled, 2 × 2 factorial design comparing BASC versus standard behavioral treatment (ST) and varenicline versus placebo, taking place in research clinics at two urban universities in the United States. Participants comprised 300 hundred adult smokers with current or past MDD.

INTERVENTIONS

BASC integrated behavioral activation therapy and ST to increase engagement in rewarding activities by reducing avoidance, withdrawal and inactivity associated with depression. ST was based on the 2008 PHS Clinical Practice Guideline. Both treatments consisted of eight 45-min sessions delivered between weeks 1 and 12. Varenicline and placebo were administered for 12 weeks between weeks 2 and 14.

MEASUREMENTS

Primary outcomes were bioverified intent-to-treat (ITT) 7-day point-prevalence abstinence at 27 weeks and adverse events (AEs).

FINDINGS

No significant interaction was detected between behavioral treatment and pharmacotherapy at 27 weeks (χ2 (1)  = 0.19, P = 0.67). BASC and ST did not differ (χ2 (1)  = 0.43, P = 0.51). Significant differences in ITT abstinence rates (χ2 (1)  = 4.84, P = 0.03) emerged among pharmacotherapy arms (16.2% for varenicline, 7.5% for placebo), with results favoring varenicline over placebo (rate ratio = 2.16, 95% confidence interval = 1.08, 4.30). All significant differences in AE rates after start of medication were higher for placebo than varenicline.

CONCLUSION

A randomized trial in smokers with major depressive disorder found that varenicline improved smoking abstinence versus placebo at 27 weeks without elevating rates of adverse events. Behavioral activation for smoking cessation did not outperform standard behavioral treatment, with or without adjunctive varenicline therapy.

Varenicline and counseling for vaping cessation: a double-blind, randomized, parallel-group, placebo-controlled trial

BACKGROUND

Vaping cessation is virtually unexplored. The efficacy and safety of varenicline for vaping cessation has not been studied and rigorous research is required to advance best practice and outcomes for people who use electronic cigarettes (EC) and want to quit. The objective is to evaluate the efficacy and safety of varenicline (1 mg BID, administered for 12 weeks, with follow-up to week 24) combined with vaping cessation counseling in exclusive daily EC users intending to quit vaping.

METHODS

Design: Double-blind, randomized, parallel-group, placebo-controlled trial.

SETTING

The study took place at a University-run smoking cessation center.

PARTICIPANTS

People who exclusively use ECs daily and intend to quit vaping.

INTERVENTION

A total of 140 subjects were randomized to either varenicline (1 mg, administered twice daily for 12 weeks) plus counseling or placebo treatment (administered twice daily, for 12 weeks) plus counseling. The trial consisted of a 12-week treatment phase followed by a 12-week follow-up, nontreatment phase.

MAIN OUTCOMES AND MEASURES

The primary efficacy endpoint of the study was biochemically validated continuous abstinence rate (CAR) at weeks 4 to 12. Secondary efficacy end points were CAR at weeks 4 to 24 and 7-day point prevalence of vaping abstinence at weeks 12 and 24.

RESULTS

CAR was significantly higher for varenicline vs placebo at each interval: weeks 4-12, 40.0% and 20.0%, respectively (OR = 2.67, 95% CI = [1.25-5.68], P = 0.011); weeks 4-24, 34.3% for varenicline with counseling and 17.2% for placebo with counseling (OR = 2.52, 95% CI = [1.14-5.58], P = 0.0224). The 7-day point prevalence of vaping abstinence was also higher for the varenicline than placebo at each time point. Serious adverse events were infrequent in both groups and not treatment-related.

CONCLUSIONS

The findings of the present RCT indicate that inclusion of varenicline in a vaping cessation program for people who use electronic cigarettes and intending to quit may result in prolonged abstinence. These positive findings establish a benchmark of intervention effectiveness, may support the use of varenicline combined with counseling in vaping cessation programs, and may also help guiding future recommendations by health authorities and healthcare providers.

TRIAL REGISTRATION

The study has been registered in EUDRACT with Trial registration ID: 2016-000339-42.

Nicotine receptor partial agonists for smoking cessation

Background

Nicotine receptor partial agonists may help people to stop smoking by a combination of maintaining moderate levels of dopamine to counteract withdrawal symptoms (acting as an agonist) and reducing smoking satisfaction (acting as an antagonist). This is an update of a Cochrane Review first published in 2007.

Objectives

To assess the effectiveness of nicotine receptor partial agonists, including varenicline and cytisine, for smoking cessation.

Search methods

We searched the Cochrane Tobacco Addiction Group's Specialised Register in April 2022 for trials, using relevant terms in the title or abstract, or as keywords. The register is compiled from searches of CENTRAL, MEDLINE, Embase, and PsycINFO. 

Selection criteria

We included randomised controlled trials that compared the treatment drug with placebo, another smoking cessation drug, e‐cigarettes, or no medication. We excluded trials that did not report a minimum follow‐up period of six months from baseline.

Data collection and analysis

We followed standard Cochrane methods. Our main outcome was abstinence from smoking at longest follow‐up using the most rigorous definition of abstinence, preferring biochemically validated rates where reported. We pooled risk ratios (RRs), using the Mantel‐Haenszel fixed‐effect model. We also reported the number of people reporting serious adverse events (SAEs).

Main results

We included 75 trials of 45,049 people; 45 were new for this update. We rated 22 at low risk of bias, 18 at high risk, and 35 at unclear risk.

We found moderate‐certainty evidence (limited by heterogeneity) that cytisine helps more people to quit smoking than placebo (RR 1.30, 95% confidence interval (CI) 1.15 to 1.47; I2 = 83%; 4 studies, 4623 participants), and no evidence of a difference in the number reporting SAEs (RR 1.04, 95% CI 0.78 to 1.37; I2 = 0%; 3 studies, 3781 participants; low‐certainty evidence). SAE evidence was limited by imprecision. We found no data on neuropsychiatric or cardiac SAEs.

We found high‐certainty evidence that varenicline helps more people to quit than placebo (RR 2.32, 95% CI 2.15 to 2.51; I2 = 60%, 41 studies, 17,395 participants), and moderate‐certainty evidence that people taking varenicline are more likely to report SAEs than those not taking it (RR 1.23, 95% CI 1.01 to 1.48; I2 = 0%; 26 studies, 14,356 participants). While point estimates suggested increased risk of cardiac SAEs (RR 1.20, 95% CI 0.79 to 1.84; I2 = 0%; 18 studies, 7151 participants; low‐certainty evidence), and decreased risk of neuropsychiatric SAEs (RR 0.89, 95% CI 0.61 to 1.29; I2 = 0%; 22 studies, 7846 participants; low‐certainty evidence), in both cases evidence was limited by imprecision, and confidence intervals were compatible with both benefit and harm.

Pooled results from studies that randomised people to receive cytisine or varenicline found no clear evidence of difference in quit rates (RR 1.00, 95% CI 0.79 to 1.26; I2 = 65%; 2 studies, 2131 participants; low‐certainty evidence) and reported SAEs (RR 0.67, 95% CI 0.44 to 1.03; I2 = 45%; 2 studies, 2017 participants; low‐certainty evidence). However, the evidence was limited by imprecision, and confidence intervals incorporated the potential for benefit from either cytisine or varenicline. We found no data on neuropsychiatric or cardiac SAEs.

We found high‐certainty evidence that varenicline helps more people to quit than bupropion (RR 1.36, 95% CI 1.25 to 1.49; I2 = 0%; 9 studies, 7560 participants), and no clear evidence of difference in rates of SAEs (RR 0.89, 95% CI 0.61 to 1.31; I2 = 0%; 5 studies, 5317 participants), neuropsychiatric SAEs (RR 1.05, 95% CI 0.16 to 7.04; I2 = 10%; 2 studies, 866 participants), or cardiac SAEs (RR 3.17, 95% CI 0.33 to 30.18; I2 = 0%; 2 studies, 866 participants). Evidence of harms was of low certainty, limited by imprecision.

We found high‐certainty evidence that varenicline helps more people to quit than a single form of nicotine replacement therapy (NRT) (RR 1.25, 95% CI 1.14 to 1.37; I2 = 28%; 11 studies, 7572 participants), and low‐certainty evidence, limited by imprecision, of fewer reported SAEs (RR 0.70, 95% CI 0.50 to 0.99; I2 = 24%; 6 studies, 6535 participants). We found no data on neuropsychiatric or cardiac SAEs.

We found no clear evidence of a difference in quit rates between varenicline and dual‐form NRT (RR 1.02, 95% CI 0.87 to 1.20; I2 = 0%; 5 studies, 2344 participants; low‐certainty evidence, downgraded because of imprecision). While pooled point estimates suggested increased risk of SAEs (RR 2.15, 95% CI 0.49 to 9.46; I2 = 0%; 4 studies, 1852 participants) and neuropsychiatric SAEs (RR 4.69, 95% CI 0.23 to 96.50; I2 not estimable as events only in 1 study; 2 studies, 764 participants), and reduced risk of cardiac SAEs (RR 0.32, 95% CI 0.01 to 7.88; I2 not estimable as events only in 1 study; 2 studies, 819 participants), in all three cases evidence was of low certainty and confidence intervals were very wide, encompassing both substantial harm and benefit.

Authors' conclusions

Cytisine and varenicline both help more people to quit smoking than placebo or no medication. Varenicline is more effective at helping people to quit smoking than bupropion, or a single form of NRT, and may be as or more effective than dual‐form NRT. People taking varenicline are probably more likely to experience SAEs than those not taking it, and while there may be increased risk of cardiac SAEs and decreased risk of neuropsychiatric SAEs, evidence was compatible with both benefit and harm. Cytisine may lead to fewer people reporting SAEs than varenicline. Based on studies that directly compared cytisine and varenicline, there may be no difference or a benefit from either medication for quitting smoking.

Future trials should test the effectiveness and safety of cytisine compared with varenicline and other pharmacotherapies, and should also test variations in dose and duration. There is limited benefit to be gained from more trials testing the effect of standard‐dose varenicline compared with placebo for smoking cessation. Further trials on varenicline should test variations in dose and duration, and compare varenicline with e‐cigarettes for smoking cessation.

Can medications like varenicline and cytisine (nicotine receptor partial agonists) help people to stop smoking and do they cause unwanted effects?

Key messages

· Varenicline can help people to stop smoking for at least 6 months. Evidence shows it works better than bupropion and using only one type of nicotine replacement therapy (e.g. only patches). Quit rates might be similar to using more than one type of nicotine replacement therapy at the same time (e.g. patches and gum together).

· Cytisine can help people to stop smoking for at least 6 months. It may work as well as varenicline, but future evidence may show that while it helps, it is not quite as helpful as varenicline.

· Future studies should test the effectiveness and safety of cytisine compared with varenicline and other stop‐smoking medications, and should also  investigate giving cytisine or varenicline at different doses and for different lengths of time.

What are 'nicotine receptor partial agonists'?

Smoking tobacco is extremely bad for people’s health. For people who smoke, quitting is the best thing they can do to improve their health. Many people find it difficult to quit smoking. Nicotine receptor partial agonists (NRPAs) are a type of medication used to help people to stop smoking. They help to reduce the withdrawal symptoms people experience when they stop smoking, like cravings and unpleasant mood changes. They also reduce the pleasure people usually experience when they smoke. The most widely‐available treatment in this drug type is varenicline. Cytisine is another, similar medication. They may cause unwanted effects such as feeling sick (nausea) and other stomach problems, difficulties sleeping, abnormal dreams, and headache. They may also lead to potentially serious unwanted effects, such as suicidal thoughts, heart problems and raised blood pressure.

What did we want to find out?

We wanted to find out if using NRPAs can help people to quit smoking, and if they cause unwanted effects. We wanted to know:

· how many people stopped smoking for at least 6 months; and

· how many people had unwanted effects.

What did we do?

We searched for studies that investigated NRPAs used to help people quit smoking. People in the studies had to be chosen at random to receive an NRPA, or another NRPA, placebo (medication like the NRPA but with no active ingredients) or no treatment. They had to be adult tobacco smokers who wanted to stop smoking.

What did we find?

We found 75 studies that compared NRPAs with:

· placebo or no medicine;

· nicotine replacement therapy, such as patches or gum;

· bupropion (another medicine to help people stop smoking);

· another NRPA;

· e‐cigarettes.

The USA hosted the most studies (28 studies). Other studies took place in a range of countries across the world, some in several countries.

Main results

People are more likely to stop smoking for at least six months using varenicline than using placebo (41 studies, 17,395 people), bupropion (9 studies, 7560 people), or just one type of nicotine replacement therapy, like patches alone (11 studies, 7572 people). They may be just as likely to quit as people using two or more kinds of nicotine replacement therapy, like patches and gum together (5 studies, 2344 people).

Cytisine probably helps more people to stop smoking than placebo (4 studies, 4623 people) and may be just as effective as varenicline (2 studies, 2131 people).

For every 100 people using varenicline to stop smoking, 21 to 25 might successfully stop, compared with only 18 of 100 people using bupropion, 18 of 100 people using a single form of nicotine‐replacement therapy, and 20 of 100 using two or more kinds of nicotine‐replacement therapy. For every 100 people using cytisine to stop smoking, 18 to 23 might successfully stop.

The most common unwanted effect of varenicline is nausea, but this is mostly at mild or moderate levels and usually clears over time. People taking varenicline likely have an increased chance of a more serious unwanted effect that could result in going to hospital, however these are still rare (2.7% to 4% of people on varenicline, compared with 2.7% of people without) and may include many that are unrelated to varenicline. People taking cytisine may also have a slightly increased chance of serious unwanted effects compared with people not taking it, but this may be less likely compared with varenicline.

What are the limitations of the evidence?

The evidence for some of our results is very reliable. We’re very confident that varenicline helps people to quit smoking better than many alternatives. We’re less sure of some other results because fewer or smaller studies provided evidence.

Several results suggest one treatment is better or less harmful than another, but the opposite could still be true.

How up to date is the evidence?

The evidence is up to date to 29 April 2022.

Nicotine receptor partial agonists for smoking cessation

BACKGROUND

Nicotine receptor partial agonists may help people to stop smoking by a combination of maintaining moderate levels of dopamine to counteract withdrawal symptoms (acting as an agonist) and reducing smoking satisfaction (acting as an antagonist). This is an update of a Cochrane Review first published in 2007.

OBJECTIVES

To assess the effectiveness of nicotine receptor partial agonists, including varenicline and cytisine, for smoking cessation.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's Specialised Register in April 2022 for trials, using relevant terms in the title or abstract, or as keywords. The register is compiled from searches of CENTRAL, MEDLINE, Embase, and PsycINFO.  SELECTION CRITERIA: We included randomised controlled trials that compared the treatment drug with placebo, another smoking cessation drug, e-cigarettes, or no medication. We excluded trials that did not report a minimum follow-up period of six months from baseline.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methods. Our main outcome was abstinence from smoking at longest follow-up using the most rigorous definition of abstinence, preferring biochemically validated rates where reported. We pooled risk ratios (RRs), using the Mantel-Haenszel fixed-effect model. We also reported the number of people reporting serious adverse events (SAEs).

MAIN RESULTS

We included 75 trials of 45,049 people; 45 were new for this update. We rated 22 at low risk of bias, 18 at high risk, and 35 at unclear risk. We found moderate-certainty evidence (limited by heterogeneity) that cytisine helps more people to quit smoking than placebo (RR 1.30, 95% confidence interval (CI) 1.15 to 1.47; I² = 83%; 4 studies, 4623 participants), and no evidence of a difference in the number reporting SAEs (RR 1.04, 95% CI 0.78 to 1.37; I² = 0%; 3 studies, 3781 participants; low-certainty evidence). SAE evidence was limited by imprecision. We found no data on neuropsychiatric or cardiac SAEs. We found high-certainty evidence that varenicline helps more people to quit than placebo (RR 2.32, 95% CI 2.15 to 2.51; I² = 60%, 41 studies, 17,395 participants), and moderate-certainty evidence that people taking varenicline are more likely to report SAEs than those not taking it (RR 1.23, 95% CI 1.01 to 1.48; I² = 0%; 26 studies, 14,356 participants). While point estimates suggested increased risk of cardiac SAEs (RR 1.20, 95% CI 0.79 to 1.84; I² = 0%; 18 studies, 7151 participants; low-certainty evidence), and decreased risk of neuropsychiatric SAEs (RR 0.89, 95% CI 0.61 to 1.29; I² = 0%; 22 studies, 7846 participants; low-certainty evidence), in both cases evidence was limited by imprecision, and confidence intervals were compatible with both benefit and harm. Pooled results from studies that randomised people to receive cytisine or varenicline showed that more people in the varenicline arm quit smoking (RR 0.83, 95% CI 0.66 to 1.05; I² = 0%; 2 studies, 2131 participants; moderate-certainty evidence) and reported SAEs (RR 0.67, 95% CI 0.44 to 1.03; I² = 45%; 2 studies, 2017 participants; low-certainty evidence). However, the evidence was limited by imprecision, and confidence intervals incorporated the potential for benefit from either cytisine or varenicline. We found no data on neuropsychiatric or cardiac SAEs. We found high-certainty evidence that varenicline helps more people to quit than bupropion (RR 1.36, 95% CI 1.25 to 1.49; I² = 0%; 9 studies, 7560 participants), and no clear evidence of difference in rates of SAEs (RR 0.89, 95% CI 0.61 to 1.31; I² = 0%; 5 studies, 5317 participants), neuropsychiatric SAEs (RR 1.05, 95% CI 0.16 to 7.04; I² = 10%; 2 studies, 866 participants), or cardiac SAEs (RR 3.17, 95% CI 0.33 to 30.18; I² = 0%; 2 studies, 866 participants). Evidence of harms was of low certainty, limited by imprecision. We found high-certainty evidence that varenicline helps more people to quit than a single form of nicotine replacement therapy (NRT) (RR 1.25, 95% CI 1.14 to 1.37; I² = 28%; 11 studies, 7572 participants), and low-certainty evidence, limited by imprecision, of fewer reported SAEs (RR 0.70, 95% CI 0.50 to 0.99; I² = 24%; 6 studies, 6535 participants). We found no data on neuropsychiatric or cardiac SAEs. We found no clear evidence of a difference in quit rates between varenicline and dual-form NRT (RR 1.02, 95% CI 0.87 to 1.20; I² = 0%; 5 studies, 2344 participants; low-certainty evidence, downgraded because of imprecision). While pooled point estimates suggested increased risk of SAEs (RR 2.15, 95% CI 0.49 to 9.46; I² = 0%; 4 studies, 1852 participants) and neuropsychiatric SAEs (RR 4.69, 95% CI 0.23 to 96.50; I² not estimable as events only in 1 study; 2 studies, 764 participants), and reduced risk of cardiac SAEs (RR 0.32, 95% CI 0.01 to 7.88; I² not estimable as events only in 1 study; 2 studies, 819 participants), in all three cases evidence was of low certainty and confidence intervals were very wide, encompassing both substantial harm and benefit.

AUTHORS' CONCLUSIONS

Cytisine and varenicline both help more people to quit smoking than placebo or no medication. Varenicline is more effective at helping people to quit smoking than bupropion, or a single form of NRT, and may be as or more effective than dual-form NRT. People taking varenicline are probably more likely to experience SAEs than those not taking it, and while there may be increased risk of cardiac SAEs and decreased risk of neuropsychiatric SAEs, evidence was compatible with both benefit and harm. Cytisine may lead to fewer people reporting SAEs than varenicline. Based on studies that directly compared cytisine and varenicline, there may be a benefit from varenicline for quitting smoking, however further evidence could strengthen this finding or demonstrate a benefit from cytisine. Future trials should test the effectiveness and safety of cytisine compared with varenicline and other pharmacotherapies, and should also test variations in dose and duration. There is limited benefit to be gained from more trials testing the effect of standard-dose varenicline compared with placebo for smoking cessation. Further trials on varenicline should test variations in dose and duration, and compare varenicline with e-cigarettes for smoking cessation.

The Blinded-Dose Purchase Task: assessing hypothetical demand based on cocaine, methamphetamine, and alcohol administration

RATIONALE

Behavioral economic drug purchase tasks quantify the reinforcing value of a drug (i.e., demand). Although widely used to assess demand, drug expectancies are rarely accounted for and may introduce variability across participants given diverse drug experiences.

OBJECTIVES

Three experiments validated and extended previous hypothetical purchase tasks by using blinded drug dose as a reinforcing stimulus, and determined hypothetical demand for experienced effects while controlling for drug expectancies.

METHODS

Across three double-blind, placebo-controlled, within-subject experiments, cocaine (0, 125, 250 mg/70 kg; n=12), methamphetamine (0, 20, 40 mg; n=19), and alcohol (0, 1 g/kg alcohol; n=25) were administered and demand was assessed using the Blinded-Dose Purchase Task. Participants answered questions regarding simulated purchasing of the blinded drug dose across increasing prices. Demand metrics, subjective effects, and self-reported real-world monetary spending on drugs were evaluated.

RESULTS

Data were well modeled by the demand curve function, with significantly higher intensity (purchasing at low prices) for active drug doses compared to placebo for all experiments. Unit-price analyses revealed more persistent consumption across prices (lower α) in the higher compared to lower active dose condition for methamphetamine (a similar non-significant finding emerged for cocaine). Significant associations between demand metrics, peak subjective effects, and real-world spending on drugs also emerged across all experiments.

CONCLUSIONS

Orderly demand curve data revealed differences across drug and placebo conditions, and relations to real-world measures of drug spending, and subjective effects. Unit-price analyses enabled parsimonious comparisons across doses. Results lend credence to the validity of the Blinded-Dose Purchase Task, which allows for control of drug expectancies.

A Brief Introduction to Human Behavioral Pharmacology: Methods, Design Considerations and Ethics

Human behavioral pharmacology methods have been used to rigorously evaluate the effects of a range of centrally acting drugs in humans under controlled conditions for decades. Methods like drug self-administration and drug discrimination have been adapted from nonhuman laboratory animal models. Because humans have the capacity to communicate verbally, self-report methods are also commonly used to understand drug effects. This perspective article provides an overview of these traditional human behavioral pharmacology methods and introduces some novel methodologies that have more recently been adapted for use in the field. Design (e.g., using placebo controls, testing multiple doses) and ethical (e.g., avoiding enrollment of individuals seeking treatment, determining capacity to consent) considerations that must be addressed when conducting these types of studies are also described.

Behavioral economic analysis of topiramate pharmacotherapy for alcohol: a placebo-controlled investigation of effects on alcohol reinforcing value and delayed reward discounting

RATIONALE

Pharmacotherapies are an important clinical strategy for treating alcohol use disorder and an understanding of their functional mechanisms can inform optimal use. Behavioral economics provides a translational platform that may advance our understanding of the motivational impacts of pharmacotherapies.

OBJECTIVES

This secondary analysis study examined the effect of topiramate, a promising pharmacotherapy for treating alcohol use disorder, on two behavioral economic domains, the reinforcing value of alcohol (alcohol demand and alcohol-specific monetary expenditures) and delayed reward discounting (preference for smaller immediate rewards over larger delayed rewards).

METHODS

A double-blind randomized placebo-controlled study (n = 99) was conducted with non-treatment seeking heavy drinkers, comparing topiramate (target dose of 200 mg/day titrated for 3 weeks and remained at the target dose for 2 weeks) to matched placebo.

RESULTS

We found that compared to placebo, topiramate reduced the reinforcing value of alcohol, as shown by a reduction in two alcohol demand indices (intensity and Omax), money spent per week on alcohol and an almost a 50% increase in days without expenditures on alcohol from baseline. Directionally consistent patterns were also present for breakpoint and elasticity (ps = .08). No significant effects were found for delayed reward discounting.

CONCLUSIONS

This study provides evidence that topiramate reduces alcohol's reinforcing value as measured by alcohol demand and alcohol expenditure. More broadly, these findings support the utility of behavioral economics for understanding how medications reduce alcohol use.

Effects of episodic future thinking on reinforcement pathology during smoking cessation treatment among individuals with substance use disorders

RATIONALE

Reinforcer pathology (RP) is a theoretical model based on two processes: delay discounting (DD) and drug demand. Given that RP has been shown to have a predictive value on smoking behaviors, several studies have explored which interventions can reduce RP. Consistent with the RP framework, episodic future thinking (EFT) has shown effects on treatment outcomes and RP processes. The vast majority of studies that assess the effects of EFT on RP consist of experimental studies, and no previous research has tested these effects in a clinical sample of smokers.

OBJECTIVES

The primary aim of this study was to assess the effects of EFT on RP throughout the course of a smoking cessation intervention in smokers with substance use disorders (SUDs).

METHODS

Participants were randomized to cognitive behavior therapy (CBT) + EFT (n = 39) or CBT + EFT + contingency management (n = 33). Cotinine, frequency of EFT practices, cigarette purchase task (CPT), and DD were evaluated in treatment sessions. Mixed-effects model repeated measures analysis was used to explore DD and CPT in-treatment changes as a function of EFT practices and cotinine levels.

RESULTS

Greater practice of the EFT component significantly reduced cigarette demand (p < .020) as well as DD (p = .003). Additionally, a greater reduction in cotinine levels coupled with greater EFT practice led to a greater decrease in cigarette demand (p < .014).

CONCLUSIONS

EFT reduced the two facets of RP in treatment-seeking smokers with SUDs.

Imagining the Future: Future Imagination Training Decreases Delay Discounting Among Internet Addicts and Non-Problematic Users

To test whether future imagination can reduce the delay discounting rate of the Internet addicts, we recruited 40 Internet addicts (treatment sample) and 39 non-problematic users (control sample). We used a 2 (participant type: individuals with Internet addiction vs. non-problematic users) × 2 (training type: future event imagination training vs. control condition) × 2 (training session: first session vs. final session) mixed-subjects design to test our hypothesis. The participant type and training type were between the subjects and the training session was within the subject. Half of each sample (the Internet addicts and non-problematic users) was randomly assigned to complete five sessions of future imagination training and the other half was assigned to describe some daily events they had observed. We used the Barratt Impulsivity Scale (BIS) and delay discounting task to assess our outcome variable, such as addiction, impulsivity, and delay discounting rate. The results showed that the future imagination training significantly reduced the delay discounting rate (also for impulsivity and addiction) for both the Internet addicts and non-problematic users than the control condition. Besides, the negative effect of future imagination training on the delay discounting rates (for impulsivity and addiction) remained consistent across the five training sessions. These findings suggest that the future imagination training can be a useful approach to reduce the impulsivity among those who are addicted to the Internet.

Smoking cessation medicines and e-cigarettes: a systematic review, network meta-analysis and cost-effectiveness analysis

BACKGROUND

Cigarette smoking is one of the leading causes of early death. Varenicline [Champix (UK), Pfizer Europe MA EEIG, Brussels, Belgium; or Chantix (USA), Pfizer Inc., Mission, KS, USA], bupropion (Zyban; GlaxoSmithKline, Brentford, UK) and nicotine replacement therapy are licensed aids for quitting smoking in the UK. Although not licensed, e-cigarettes may also be used in English smoking cessation services. Concerns have been raised about the safety of these medicines and e-cigarettes.

OBJECTIVES

To determine the clinical effectiveness, safety and cost-effectiveness of smoking cessation medicines and e-cigarettes.

DESIGN

Systematic reviews, network meta-analyses and cost-effectiveness analysis informed by the network meta-analysis results.

SETTING

Primary care practices, hospitals, clinics, universities, workplaces, nursing or residential homes.

PARTICIPANTS

Smokers aged ≥ 18 years of all ethnicities using UK-licensed smoking cessation therapies and/or e-cigarettes.

INTERVENTIONS

Varenicline, bupropion and nicotine replacement therapy as monotherapies and in combination treatments at standard, low or high dose, combination nicotine replacement therapy and e-cigarette monotherapies.

MAIN OUTCOME MEASURES

Effectiveness - continuous or sustained abstinence. Safety - serious adverse events, major adverse cardiovascular events and major adverse neuropsychiatric events.

DATA SOURCES

Ten databases, reference lists of relevant research articles and previous reviews. Searches were performed from inception until 16 March 2017 and updated on 19 February 2019.

REVIEW METHODS

Three reviewers screened the search results. Data were extracted and risk of bias was assessed by one reviewer and checked by the other reviewers. Network meta-analyses were conducted for effectiveness and safety outcomes. Cost-effectiveness was evaluated using an amended version of the Benefits of Smoking Cessation on Outcomes model.

RESULTS

Most monotherapies and combination treatments were more effective than placebo at achieving sustained abstinence. Varenicline standard plus nicotine replacement therapy standard (odds ratio 5.75, 95% credible interval 2.27 to 14.90) was ranked first for sustained abstinence, followed by e-cigarette low (odds ratio 3.22, 95% credible interval 0.97 to 12.60), although these estimates have high uncertainty. We found effect modification for counselling and dependence, with a higher proportion of smokers who received counselling achieving sustained abstinence than those who did not receive counselling, and higher odds of sustained abstinence among participants with higher average dependence scores. We found that bupropion standard increased odds of serious adverse events compared with placebo (odds ratio 1.27, 95% credible interval 1.04 to 1.58). There were no differences between interventions in terms of major adverse cardiovascular events. There was evidence of increased odds of major adverse neuropsychiatric events for smokers randomised to varenicline standard compared with those randomised to bupropion standard (odds ratio 1.43, 95% credible interval 1.02 to 2.09). There was a high level of uncertainty about the most cost-effective intervention, although all were cost-effective compared with nicotine replacement therapy low at the £20,000 per quality-adjusted life-year threshold. E-cigarette low appeared to be most cost-effective in the base case, followed by varenicline standard plus nicotine replacement therapy standard. When the impact of major adverse neuropsychiatric events was excluded, varenicline standard plus nicotine replacement therapy standard was most cost-effective, followed by varenicline low plus nicotine replacement therapy standard. When limited to licensed interventions in the UK, nicotine replacement therapy standard was most cost-effective, followed by varenicline standard.

LIMITATIONS

Comparisons between active interventions were informed almost exclusively by indirect evidence. Findings were imprecise because of the small numbers of adverse events identified.

CONCLUSIONS

Combined therapies of medicines are among the most clinically effective, safe and cost-effective treatment options for smokers. Although the combined therapy of nicotine replacement therapy and varenicline at standard doses was the most effective treatment, this is currently unlicensed for use in the UK.

FUTURE WORK

Researchers should examine the use of these treatments alongside counselling and continue investigating the long-term effectiveness and safety of e-cigarettes for smoking cessation compared with active interventions such as nicotine replacement therapy.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42016041302.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 25, No. 59. See the NIHR Journals Library website for further project information.

Decreased cocaine demand following contingency management treatment

A hypothetical cocaine purchasing task (CocPT) was used to assess changes in cocaine demand in the context of contingency management (CM) treatment for cocaine use disorder (CUD). Participants (N = 89) were treatment-seeking individuals with CUD receiving 4 weeks of abstinence-based, high-magnitude CM. Treatment response (vs. non-response) was operationally defined as the submission of 6 consecutive cocaine-negative urine samples across two weeks. The CPT was assessed at baseline, week 2, and week 5. Demand data were well described by the exponentiated demand model, and baseline demand indices (Q0, Pmax, breakpoint, essential value) were significantly associated with self-report measures of cocaine use. The probability of being a zero-responder reporting zero cocaine consumption at all prices significantly increased over the course of treatment, and was greater among treatment responders vs. non-responders. Among non-zero demand data, decreases in Omax, Pmax, breakpoint, and essential value were observed over the course of CM treatment, favoring responders. To our knowledge, this is the first study to assess change in cocaine demand in the context of CM treatment targeting cocaine abstinence. Our results support the utility of cocaine demand as a measure for both identifying individuals with greater treatment need and tracking relapse risk over the course of treatment.

Effects of acute distress and tobacco cues on tobacco demand

INTRODUCTION

Cigarette demand, or relative value, can be assessed via analysis of performance on a hypothetical behavioral economic cigarette purchase task (CPT). Substance purchase tasks are highly amenable to manipulation, namely, external stimuli, instructional changes, or acute stressors. In this regard, the current secondary analysis evaluates the role a novel, computerized stress induction paradigm, the Contextual-Frustration Intolerance Typing Task (C-FiTT), plays in eliciting varying levels of stress and resulting demand.

METHOD

Daily smokers (n = 484) completed the C-FiTT wherein they were randomly assigned to one of five distress conditions: combination of task difficulty (low or high difficulty) with neutral or withdrawal cues, and a neutral control group. Tobacco demand was assessed immediately following the distress task using the hypothetical CPT.

RESULTS

The C-FiTT distress-induction task significantly increased key cigarette demand indices, including price at maximum expenditure (Pmax) and first price where consumption was suppressed to zero (breakpoint). Moreover, demand increased with severity of C-FiTT condition, with the high-difficulty condition resulting in significantly higher breakpoint and Pmax, compared to other conditions. C-FiTT condition was not related to a significant increase in Omax, intensity, or elasticity.

DISCUSSION

The novel C-FiTT paradigm produced comparable effects on tobacco demand relative to in vivo withdrawal induction, indicating that the C-FiTT is a viable procedure by which to influence demand. Reduction of internal and external stressors may be effective in lowering motivation for tobacco. These results highlight the importance of state distress in tobacco demand, and offer a potential avenue for intervention.

Purchase task sensitivity to drug and nondrug reinforcers in opioid-agonist treatment patients

The behavioral economics of substance abuse has been increasingly recognized as a method of determining the value of abused substances for individuals who use those substances. It has been hypothesized that such analyses could serve as a clinical tool and that demand functions can be targeted predictors for the level of intervention necessary. This study evaluated the sensitivity of a demand task in 2 patient groups in a medication assisted treatment program (methadone maintenance), those who had used opioids in the last 2 months and those who had not used opioids in at least 18 months. Demand for 7 drugs and a control was assessed using hypothetical purchase tasks. Participants maintaining long-term abstinence had significantly higher α (sensitivity to price) and lower Q₀ (intensity of demand) for heroin than participants who had recently used opioids. Further research is necessary to illustrate if treatment is responsible for this reduction in demand. If so, demand analyses may provide clinical utility as an aid for treatment planning or as a target for treatment.

The impact of three weeks of pre-quit varenicline on reinforcing value and craving for cigarettes in a laboratory choice procedure

RATIONALE

Varenicline, a partial nicotinic agonist, is theorized to attenuate pre-quit smoking reinforcement and post-quit withdrawal and craving. However, the mechanisms of action have not been fully characterized, as most studies employ only retrospective self-report measures, hypothetical indices of reinforcing value, and/or nontreatment-seeking samples.

OBJECTIVES

The current research examined the impact of pre-quit varenicline (vs. placebo) on laboratory measures of smoking and food (vs. water) reinforcement and craving.

METHODS

Participants were 162 treatment-seeking smokers enrolled in a randomized controlled trial of smoking cessation ( clinicaltrials.gov ID: NCT03262662). Participants completed two laboratory sessions: a pre-treatment session, ~ 1 week prior to beginning varenicline or placebo, and an active treatment session, after ~ 3 weeks of treatment. At each session, participants completed a laboratory choice procedure; on each of 36 trials, a lit cigarette, food item, or cup of water was randomly presented. Participants reported level of craving and spent $0.01-0.25 to have a corresponding 5-95% chance to sample the cue.

RESULTS

As predicted, spending was significantly higher on cigarette trials than water trials, and varenicline resulted in a greater between-session decline in spending on cigarette trials (but not water) than did placebo. Cigarette craving was enhanced in the presence of smoking cues compared to water, but neither average (tonic) cigarette craving nor cue-specific cigarette craving was significantly influenced by varenicline. Food spending and craving were generally unaffected by varenicline treatment.

CONCLUSIONS

These laboratory data from treatment-seeking smokers provide the strongest evidence to date that varenicline selectively attenuates smoking reinforcement prior to quitting.

Behavioral economic measurement of cigarette demand: A descriptive review of published approaches to the cigarette purchase task

The cigarette purchase task (CPT) is a behavioral economic method for assessing demand for cigarettes. Growing interest in behavioral correlates of tobacco use in clinical and general populations as well as empirical efforts to inform policy has seen an increase in published articles employing the CPT. Accordingly, an examination of the published methods and procedures for obtaining these behavioral economic metrics is timely. The purpose of this investigation was to provide a review of published approaches to using the CPT. We searched specific Boolean operators (["behavioral economic" AND "purchase task"] OR ["demand" AND "cigarette"]) and identified 49 empirical articles published through the year 2018 that reported administering a CPT. Articles were coded for participant characteristics (e.g., sample size, population type, age), CPT task structure (e.g., price framing, number and sequence of prices; vignettes, contextual factors), and data analytic approach (e.g., method of generating indices of cigarette demand). Results of this review indicate no standard approach to administering the CPT and underscore the need for replicability of these behavioral economic measures for the purpose of guiding clinical and policy decisions. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Lower self-efficacy and greater depressive symptoms predict greater failure to recover from a single lapse cigarette

OBJECTIVE

Smoking reexposure after a quit attempt (i.e., lapse) increases relapse risk, but lapse recovery is possible. Using a 6-day analogue model of smoking cessation and lapse, this study tested the effect of a single lapse cigarette on the risk of subsequent smoking. Abstinence self-efficacy (ASE) and depressive symptoms (using the Center for Epidemiological Studies Depression Scale, CES-D) were also examined as hypothesized moderators of lapse recovery.

METHOD

After receiving cessation counseling and achieving 2 days of incentivized abstinence, 54 daily smokers (mean age: 41 years, 61% African American, 63% male) were randomly assigned to smoke 1 cigarette or to a no-lapse control condition. Participants were then offered monetary incentives to abstain for 3 more days and smoking was monitored.

RESULTS

Compared to the control condition, participants who experienced a lapse had a 2.5 times greater risk of smoking in the first 24 hours Furthermore, a lapse resulted in much greater risk of subsequent smoking compared to the control condition among individuals with lower postquit ASE scores (p = .044) and greater CES-D scores (p = .040).

CONCLUSIONS

These findings provide preliminary evidence that a single lapse cigarette after quitting plays a causal role in subsequent smoking and suggest that individuals with lower postquit ASE and greater depressive symptoms are less likely to recover from a lapse. Future research should investigate factors associated with lapse recovery and failure so that effective lapse-responsive strategies can be developed. Laboratory models provide an efficient and controlled method to examine such processes. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Accumbens neuroimmune signaling and dysregulation of astrocytic glutamate transport underlie conditioned nicotine-seeking behavior

Nicotine self-administration is associated with decreased expression of the glial glutamate transporter (GLT-1) and the cystine-glutamate exchange protein xCT within the nucleus accumbens core (NAcore). N-acetylcysteine (NAC) has been shown to restore these proteins in a rodent model of drug addiction and relapse. However, the specific molecular mechanisms driving its inhibitory effects on cue-induced nicotine reinstatement are unknown. Here, we confirm that extinction of nicotine-seeking behavior is associated with impaired NAcore GLT-1 function and expression and demonstrates that reinstatement of nicotine seeking rapidly enhances membrane fraction GLT-1 expression. Extinction and cue-induced reinstatement of nicotine seeking was also associated with increased tumor necrosis factor alpha (TNFα) and decreased glial fibrillary acidic protein (GFAP) expression in the NAcore. NAC treatment (100 mg/kg/day, i.p., for 5 d) inhibited cue-induced nicotine seeking and suppressed AMPA to NMDA current ratios, suggesting that NAC reduces NAcore postsynaptic excitability. In separate experiments, rats received NAC and an antisense vivo-morpholino to selectively suppress GLT-1 expression in the NAcore during extinction and were subsequently tested for cue-induced reinstatement of nicotine seeking. NAC treatment rescued NAcore GLT-1 expression and attenuated cue-induced nicotine seeking, which was blocked by GLT-1 antisense. NAC also reduced TNFα expression in the NAcore. Viral manipulation of the NF-κB pathway, which is downstream of TNFα, revealed that cue-induced nicotine seeking is regulated by NF-κB pathway signaling in the NAcore independent of GLT-1 expression. Ultimately, these results are the first to show that immunomodulatory mechanisms may regulate known nicotine-induced alterations in glutamatergic plasticity that mediate cue-induced nicotine-seeking behavior.

Behavioral economic demand as a unifying language for addiction science: Promoting collaboration and integration of animal and human models

The intersection of pharmacological, psychological, and economic theory within behavioral economics has helped advance an understanding of substance use disorder. A notable contribution of this approach is the conceptualization of reinforcement from a behavioral economic demand perspective. Demand analyses provide a multidimensional view of reinforcement in which distinct behavioral mechanisms are measured that impact decision making and drug consumption. This review describes the state of research on behavioral economic demand as a common language for addiction science researchers across varied model systems and stages of a translational continuum. We first provide an overview of the theoretical concepts and procedures used to evaluate demand in animal and human models. The potential for demand to serve as a common language for diverse research groups in psychopharmacology and addiction science (e.g., those evaluating neurobehavioral outcomes, medications development, clinical practice) is then described. An overview is also provided of existing empirical studies that, while small in number, suggest good linguistic and conceptual overlap between animal and human demand models when studying biological, environmental, and pharmacological individual difference vulnerabilities underlying drug-taking behavior. Refinement of methodological procedures and incorporation of more nuanced environmental features should help improve correspondence between animal and human demand studies as well as clinical translation of such findings. Our hope is that this review and commentary ultimately serves as inspiration for new collaborative efforts involving behavioral economic demand between animal and human researchers who share a common goal of improving substance use treatment outcomes and broader psychological wellbeing. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Experimental manipulations of behavioral economic demand for addictive commodities: a meta-analysis

BACKGROUND AND AIMS

Reinforcing value, an index of motivation for a drug, is commonly measured using behavioral economic purchase tasks. State-oriented purchase tasks are sensitive to phasic manipulations, but with heterogeneous methods and findings. The aim of this meta-analysis was to characterize the literature examining manipulations of reinforcing value, as measured by purchase tasks and multiple-choice procedures, to inform etiological models and treatment approaches METHODS: A random-effects meta-analysis of published findings in peer-reviewed articles. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol, studies were gathered through searches in PsycINFO and PubMed/MEDLINE (published 22 May 2018). Searches returned 34 unique studies (aggregate sample n = 2402; average sample size = 68.94) yielding 126 effect sizes. Measurements included change (i.e. Cohen's d) in six behavioral economic indices (intensity, breakpoint, O_max , P_max , elasticity, cross-over point) in relation to six experimental manipulations (cue exposure, stress/negative affect, reinforcer magnitude, pharmacotherapy, behavioral interventions, opportunity cost).

RESULTS

Cue exposure (d range = 0.25-0.44, all Ps < 0.05) and reinforcer magnitude [d = 0.60; 95% confidence interval (CI) = 0.18, 1.01; P < 0.005] manipulations resulted in significant increases in behavioral economic demand across studies. Stress/negative affect manipulations also resulted in a small, significant increase in O_max (d = 0.18; 95% CI = 0.01, 0.34; P = 0.03); all other effect sizes for negative affect/stress were non-significant, albeit similar in size (d range = 0.14-0.18). In contrast, pharmacotherapy (d range = -0.37 to -0.49; Ps < 0.04), behavioral intervention (d = -0.36 to -1.13) and external contingency (d = -1.42; CI = -2.30, -0.54; P = 0.002) manipulations resulted in a significant decrease in intensity. Moderators (substance type) explained some of the heterogeneity in findings across meta-analyses.

CONCLUSIONS

In behavioral economic studies, purchase tasks and multiple-choice procedures appear to provide indices that are sensitive to manipulations found to influence motivation to consume addictive substances in field experiments.

Utilizing the commodity purchase task to evaluate behavioral economic demand for illicit substances: a review and meta-analysis

BACKGROUND ANDAIMS

The commodity purchase task is a simulated demand procedure that is easy and quick to complete (< 5 minutes) as well as adaptable for remote delivery and use with varied study populations. The purpose of this meta-analysis was to synthesize research using the commodity purchase task with illicit substances to evaluate the magnitude of omnibus effects sizes and moderators of the correlation of demand indices with quantity-frequency (QF) and severity measures.

DESIGN

Random-effects meta-analyses and meta-regressions involving studies with cross-sectional correlational designs.

SETTING AND PARTICIPANTS

Eleven studies, 10 outcomes and 2146 participants from two countries (USA and UK) published up to 1 October 2018.

MEASUREMENTS

Omnibus effect sizes (correlation coefficients) of five demand indices from the commodity purchase task [intensity (unconstrained consumption), elasticity (price sensitivity), O_max (maximum expenditure), P_max (price at maximum expenditure) and breakpoint (first price of zero consumption)] with QF and severity measures. Meta-regression models tested moderators of effect sizes (i.e. sample age and sex composition, commodity type and number of prices used in the commodity purchase task).

FINDINGS

Significant omnibus effect sizes were observed with QF and severity measures for intensity (r = 0.32/0.28, QF/severity, respectively), elasticity (r = -0.14/-0.18), O_max (r = 0.30/0.29) and breakpoint (r = 0.17/0.22) values. P_max was only significantly associated with severity measures (r = 0.15). The percentage of female participants and number of prices used in the purchase task significantly moderated P_max and breakpoint effect-size estimates in that stronger associations were observed in samples with a greater percentage of women and in studies using tasks with more price points. Commodity type (cannabis versus cocaine) did not significantly moderate associations involving any demand index.

CONCLUSIONS

Behavioral economic demand as measured by the commodity purchase task is consistently correlated with measures of illicit substance use quantity-frequency and severity.

The condom purchase task: A hypothetical demand method for evaluating sexual health decision-making

Behavioral economic theory has proved useful for understanding the influence of delay and probability on sexual health decision-making. Demand is another principle at the intersection of microeconomics and psychology that has helped advance research relevant to health behaviors. The purpose of the present study was to develop and test a demand measure related to sexual health decision-making and the influence of sexually transmitted infection (STI) risk. Participants (N = 438) recruited using Amazon Mechanical Turk completed a commodity purchase task assessing hypothetical condom demand. Condom demand was evaluated at varied prices for use with hypothetical sexual partners that varied in STI risk. Demand was characterized by prototypic decreases in consumption with increases in cost. Higher partner STI risk was associated with greater intentions for condom-protected sex at no cost and smaller decreases in condom demand with increases in cost. Price sensitivity was also related to individual difference factors relevant to sexual health (e.g., alcohol use severity, lower STI knowledge). This study supports the utility of a condom purchase task for indexing condom valuation and capturing individual difference and contextual risk factors relevant to STI transmission. Future studies may leverage this methodology as a means to study sexual health decision-making.

Behavioral economic tobacco demand in relation to cigarette consumption and nicotine dependence: a meta-analysis of cross-sectional relationships

BACKGROUND AND AIMS

A cigarette purchase task (CPT) aims to characterize individual variation in the reinforcing value of tobacco. This meta-analysis estimated the associations between cigarette demand, tobacco consumption and nicotine dependence using this task.

DESIGN

A meta-analysis of cross-sectional studies identified by PubMed and PsycINFO databases was conducted. Fixed- and random-effects models were used. The study also examined the model used to derive elasticity of demand (exponential or exponentiated) as a potential moderator. Publication bias was assessed using 'fail-safe N', Begg-Mazumdar test, Egger's test, Tweedie's trim-and-fill approach and meta-regression of publication year with effect size.

SETTING

Studies from any setting that reported coefficient correlations on the tested associations.

PARTICIPANTS

Daily cigarette users (i.e. 5 to 38 cigarettes per day; n = 7649).

MEASUREMENTS

Cigarette consumption, nicotine dependence and five tobacco demand indicators: intensity (i.e. consumption at no cost), elasticity (i.e. sensitivity to rises in costs), Omax (maximum expenditure), Pmax (i.e. price at which consumption becomes elastic) and breakpoint (i.e. price at which consumption ceases).

FINDINGS

Twenty-three studies met inclusion criteria. All the CPT indices were significantly correlated with smoking behavior (rs = 0.044-0.572, Ps = 0.012-10-8 ). Medium-to-large effect size associations were present for intensity, Omax, and elasticity, whereas small effects were obtained for breakpoint and Pmax . Evidence of a moderating effect of the different elasticity modeling approaches was not present. There was limited evidence of publication bias.

CONCLUSIONS

All five demand indices derived from the cigarette purchase task by (CPT) were robustly associated with cigarette consumption and tobacco dependence. Of the demand indices, maximum expenditure, intensity and elasticity exhibited the largest magnitude associations.

Graphic Warning Labels Affect Hypothetical Cigarette Purchasing Behavior among Smokers Living with HIV

Cigarette pack graphic warning labels (GWLs) are associated with increased knowledge of tobacco-related harms; scant research has evaluated their effects on behavior among vulnerable populations. We used a behavioral economic approach to measure the effects of GWLs and price on hypothetical cigarette purchasing behavior among HIV-positive smokers. Participants (n = 222) completed a cigarette valuation task by making hypothetical choices between GWL cigarette packs at a fixed price ($7.00) and text-only warning label cigarette packs at increasing prices ($3.50 to $14.00; $0.25 increments). More than one-quarter (28.8%) of participants paid more to avoid GWLs. The remaining participants’ purchasing decisions appear to have been driven by price: 69.8% of participants chose the cheaper pack. Across all participants, overall monetary choice value observed for GWL cigarette packs (mean = $7.75) was greater than if choice was driven exclusively by price ($7.00). Most (87.4%) preferred the text-only warning label when GWL and text-only cigarette packs were equally priced. Correlation analysis indicated GWL pack preference was associated with agreement with statements that GWLs would stop individuals from having a cigarette or facilitate thoughts about quitting. These data suggest that GWLs may influence some HIV-positive smokers in such a way that they are willing to pay more to avoid seeing GWLs.

Rats choose high doses of nicotine in order to compensate for changes in its price and availability

Restricting when and where smoking can occur is a major focus of public health policies in Western countries. In conjunction with increased taxation, these approaches have contributed to a reduction in smoking uptake among adolescents, yet the consequences for established smokers are less clear. In order to further explore this relationship, we developed a novel animal model of restricted nicotine self-administration. Rats were trained to choose between three doses of nicotine (15, 30 and 60 μg/kg/infusion) under conditions where nicotine was (1) freely available at a low cost (20-second post-infusion time-out, fixed-ratio 1 [FR1]), (2) available under restricted access at a low cost (300-second post-infusion time-out, FR1), or (3) freely available at a high cost (20-second post-infusion time-out, FR5). We demonstrate that as access to nicotine is restricted or when cost increases, rats compensate for these changes by increasing their intake of the highest dose of nicotine available. This preference was impervious to treatment with the smoking cessation medication varenicline, but was reduced when the cost of the highest dose only was increased, or when nicotine was again made freely available at a low cost. These results provide the first evidence in rats that nicotine availability and cost influence nicotine choice independently of variations in nicotine and context exposure. They imply that established smokers may compensate for changes in the availability and cost of tobacco by increasing their rate of smoking when they are free to do so.

Validation of a behavioral economic purchase task for assessing drug abuse liability

Behavioral economic purchase tasks quantify drug demand (i.e. reinforcing value of a drug) and have been used extensively to assess the value of various drugs among current users. However, purchase tasks have been rarely used with unfamiliar drugs to address a compound's abuse liability, and the current study sought to validate the paradigm in this capacity. Using a double-blind placebo-controlled within-subjects drug challenge design, the study evaluated differential drug demand on an experimental drug purchase task for a 20 mg dose of oral D-amphetamine (versus placebo), a prototypic psychostimulant, in 98 stimulant-naïve participants. Compared with placebo, amphetamine significantly increased intensity, breakpoint and O_max , and significantly decreased elasticity. Mechanistic analyses revealed that O_max and breakpoint mediated the relationship between subjective drug effects and 'willingness to take again', a putative indicator of liability via motivation for future drug-seeking behavior. These findings validate the purchase task paradigm for quantifying the reinforcing value and, in turn, abuse liability of unfamiliar compounds, providing a foundation for a variety of future applications.

Lorcaserin decreases the reinforcing effects of heroin, but not food, in rhesus monkeys

Preclinical studies indicate that lorcaserin (Belviq®), an FDA-approved serotonin 2 C receptor agonist, may be a promising medication for the treatment of stimulant addiction. However, few studies have investigated its effects on self-administration of drugs of abuse from other pharmacological classes, including opioids. Here, adult male rhesus macaques (N = 3) responded under a fixed ratio 30 schedule of food (1-g banana-flavored pellets) and IV heroin delivery. Following stable self-administration of a range of heroin doses (0.32-32 μg/kg/inj, IV), the effects of acute pretreatment with lorcaserin (0.32-1.0 mg/kg, IM) on heroin- and food-maintained responding was determined. The ability of repeated treatment with lorcaserin (1.0 mg/kg) to produce sustained decreases in heroin and/or food intake and reinforcing strength were then analyzed using behavioral economic demand procedures. Results show that self-administration of intravenous heroin was dose-dependent, with peak responding maintained, on average, by the unit dose of 3.2 μg/kg/inj. Lorcaserin pretreatment produced a dose-dependent flattening of the dose-response function for heroin self-administration in each subject. On the other hand, lorcaserin did not decrease food-maintained responding. Repeated lorcaserin treatment reduced heroin intake by selectively decreasing its reinforcing strength, as evidenced by a leftward shift in the demand curves for heroin and the absence of comparable changes in the reinforcing strength of food. These results indicate that serotonin 2 C receptor agonists, such as lorcaserin, have behaviorally selective effects on IV self-administration behavior, and deserve further consideration as candidates for the management of opioid use disorder.

Effects of varenicline on subjective craving and relative reinforcing value of cigarettes

BACKGROUND

Varenicline is an FDA approved medication for the treatment of nicotine dependence. While the efficacy and safety of this medication have been demonstrated, success rates remain low, and efforts to understand mechanisms of efficacy are in progress. A behavioral economics framework is one unique way to examine how demand for a drug changes under different circumstances. Therefore, the current randomized placebo-controlled, cross-over study aimed to examine effects of varenicline on subjective cigarette craving and objective demand for cigarettes measured by a hypothetical behavioral economic task as well as associations between subjective craving and objective demand.

METHOD

Non-treatment seeking (n = 37) daily smokers (>10 cigarettes per day) completed a measure of subjective craving for cigarettes and the Cigarette Purchase Task following overnight nicotine abstinence. Participants completed these measures after 10 days on varenicline (1 mg twice per day) and matched placebo.

RESULTS

Analyses revealed a significant reduction in subjective craving for cigarettes while on varenicline (p = 0.01), as compared to placebo, and a sex effect such that females exhibited greater craving than males (p = 0.03). However, there were no medication × sex effects (p = 0.84). Analyses of objective demand for cigarettes found varenicline reduced maximum expenditure (Omax) (p = 0.03). Subjective craving was also associated with various indices of demand.

CONCLUSION

Results demonstrated varenicline's efficacy in attenuating subjective craving and objective demand for cigarettes and highlight the partial overlap between dimensions of acute drug motivation, namely subjective craving and behavioral economic indices of cigarette demand.

21st century neurobehavioral theories of decision making in addiction: Review and evaluation

This review critically examines neurobehavioral theoretical developments in decision making in addiction in the 21st century. We specifically compare each theory reviewed to seven benchmarks of theoretical robustness, based on their ability to address: why some commodities are addictive; developmental trends in addiction; addiction-related anhedonia; self-defeating patterns of behavior in addiction; why addiction co-occurs with other unhealthy behaviors; and, finally, means for the repair of addiction. We have included only self-contained theories or hypotheses which have been developed or extended in the 21st century to address decision making in addiction. We thus review seven distinct theories of decision making in addiction: learning theories, incentive-sensitization theory, dopamine imbalance and systems models, opponent process theory, strength models of self-control failure, the competing neurobehavioral decision systems theory, and the triadic systems theory of addiction. Finally, we have directly compared the performance of each of these theories based on the aforementioned benchmarks, and highlighted key points at which several theories have coalesced.

Effects of varenicline versus transdermal nicotine replacement therapy on cigarette demand on quit day in individuals with substance use disorders

RATIONALE

Cigarette demand is a behavioral economic measure of the relative value of cigarettes. Decreasing the value of cigarette reinforcement may help with quitting smoking.

OBJECTIVES

This study aimed to evaluate the effects of initial use of varenicline (VAR) versus nicotine replacement therapy (NRT) on demand for cigarettes on quit day among smokers with substance use disorders (SUD) and to determine whether reduced demand was associated with subsequent abstinence from smoking at 1 and 3 months.

METHODS

Participants (N = 110) were randomized to double-blind, double-placebo conditions: VAR with placebo NRT or NRT with placebo capsules. The cigarette purchase task (CPT) was used to assess demand for cigarettes at baseline and on quit day, following a 1-week medication dose run-up/placebo capsule lead-in and first day use of the patch.

RESULTS

Demand for cigarettes decreased from baseline to quit day without significant differences between medications. Reductions in CPT intensity (number of cigarettes that would be smoked if they were free) and CPT breakpoint (lowest price at which no cigarettes would be purchased) predicted greater likelihood of abstaining on quit day. Reduced intensity predicted length of abstinence at 1 and 3 months while reduced breakpoint predicted only 1 month length of abstinence.

CONCLUSIONS

Initial therapeutic doses of VAR and NRT resulted in similar reductions in cigarette reinforcement. Larger initial reductions in demand on quit day were associated with early success with abstaining from cigarettes. Behavioral economic approaches may be useful for identifying individuals who benefit less from pharmacotherapy and may need additional treatment resources.

TRIAL REGISTRATION

https://clinicaltrials.gov/ct2/show/NCT00756275.

Behavioral economic substitutability of e-cigarettes, tobacco cigarettes, and nicotine gum

The public health impact of e-cigarettes may depend on their substitutability for tobacco cigarettes. Dual users of e-cigarettes and tobacco cigarettes completed purchasing tasks in which they specified daily use levels under hypothetical conditions that varied the availability and price of e-cigarettes, tobacco cigarettes, and nicotine gum (for those with nicotine gum experience). When either e-cigarettes or tobacco cigarettes were the only available commodity, as price per puff increased, purchasing decreased, revealing similar reinforcement profiles. When available concurrently, as the price of tobacco puffs increased, purchasing of tobacco puffs decreased while purchasing of fixed-price e-cigarette puffs increased. Among those with nicotine gum experience, when the price of tobacco puffs was closest to the actual market value of tobacco puffs, e-cigarette availability decreased median tobacco puff purchases by 44% compared to when tobacco was available alone. In contrast, nicotine gum availability caused no decrease in tobacco puff purchases. E-cigarettes may serve as a behavioral economic substitute for tobacco cigarettes, and may be a superior substitute compared to nicotine gum in their ability to decrease tobacco use. Although important questions remain regarding the health impacts of e-cigarettes, these data are consistent with the possibility that e-cigarettes may serve as smoking cessation/reduction aids.

Inhibiting subthalamic nucleus decreases cocaine demand and relapse: therapeutic potential

Preclinical evidence indicates that inactivation of subthalamic nucleus (STN) may be effective for treating cocaine addiction, and therapies that target STN, e.g. deep brain stimulation, are available indicating that this may have clinical promise. Here, we assessed the therapeutic potential of STN inactivation using a translationally relevant economic approach that quantitatively describes drug-taking behavior, and tested these results with drug-seeking tasks. Economic demand for cocaine was assessed in rats (n = 11) using a within-session threshold procedure in which cocaine price (responses/mg cocaine) was sequentially increased throughout the session. Cocaine demand was assessed in this manner immediately after bilateral microinfusions into STN of either vehicle (artificial cerebrospinal fluid) or the GABAA receptor agonist muscimol. A separate group of animals (n = 8) was tested for changes in cocaine seeking either during extinction or in response to cocaine-associated cues. Muscimol-induced inhibition of STN significantly attenuated cocaine consumption at high prices, drug seeking during extinction and cued reinstatement of cocaine seeking. In contrast, STN inhibition did not reduce cocaine consumption at low prices or locomotor activity. Thus, STN inactivation reduced economic demand for cocaine and multiple measures of drug seeking during extinction. In view of the association between economic demand and addiction severity in both rat and human, these results indicate that STN inactivation has substantial clinical potential for treatment of cocaine addiction.

Oxytocin Acts in Nucleus Accumbens to Attenuate Methamphetamine Seeking and Demand

BACKGROUND

Evidence indicates that oxytocin, an endogenous peptide well known for its role in social behaviors, childbirth, and lactation, is a promising addiction pharmacotherapy. We employed a within-session behavioral-economic (BE) procedure in rats to examine oxytocin as a pharmacotherapy for methamphetamine (meth) addiction. The BE paradigm was modeled after BE procedures used to assess motivation for drugs in humans with addiction. The same BE variables assessed across species have been shown to predict later relapse behavior. Thus, the translational potential of preclinical BE studies is particularly strong.

METHODS

We tested the effects of systemic and microinfused oxytocin on demand for self-administered intravenous meth and reinstatement of extinguished meth seeking in male and female rats using a BE paradigm. Correlations between meth demand and meth seeking were assessed.

RESULTS

Female rats showed greater demand (i.e., motivation) for meth compared with male rats. In both male and female rats, meth demand predicted reinstatement of meth seeking, and systemic oxytocin decreased demand for meth and attenuated reinstatement to meth seeking. Oxytocin was most effective at decreasing meth demand and seeking in rats with the strongest motivation for drug. Finally, these effects of systemic oxytocin were mediated by actions in the nucleus accumbens.

CONCLUSIONS

Oxytocin decreases meth demand and seeking in both sexes, and these effects depend on oxytocin signaling in the nucleus accumbens. Overall, these data indicate that development of oxytocin-based therapies may be a promising treatment approach for meth addiction in humans.

Maintenance pharmacotherapy normalizes the relapse curve in recently abstinent tobacco smokers with schizophrenia and bipolar disorder

OBJECTIVE

To compare the effect of maintenance pharmacotherapy on sustained abstinence rates between recently abstinent smokers with schizophrenia and bipolar disorder (SBD) and general population smokers without psychiatric illness.

METHOD

We performed a person-level, pooled analysis of two randomized controlled trials of maintenance varenicline, conducted in adult smokers with SBD and general population smokers, controlling for severity of dependence. Smokers abstinent after 12-weeks of open varenicline treatment were randomly assigned to ≥12-weeks maintenance varenicline or identical placebo.

RESULTS

In those assigned to maintenance placebo, the abstinence rate at week-24 was lower in those with SBD than for those without psychiatric illness (29.4±1.1% vs. 61.8±0.4%, OR:0.26, 95% CI: 0.13, 0.52, p<0.001). In smokers assigned to maintenance pharmacotherapy, however, there was no effect of diagnosis on abstinence rates at week-24 (87.2±0.8% vs. 81.9±0.2%, OR: 1.68, 95% CI: 0.53, 5.32, p=0.38). Time to first lapse was shortest in those with SBD assigned to maintenance placebo (Q1=12days, 95%CI: 4, 16), longer in those without psychiatric illness assigned to maintenance placebo (Q1=17days, 95%CI: 17, 29), still longer in general-population smokers assigned to maintenance varenicline (Q1=88, 95% CI:58,91, and longest in those with SBD who received maintenance varenicline (Q1>95days, 95%CI:non-est), (Χ²_3df=96.99, p<0.0001; all pairwise comparisons p<0.001).

CONCLUSIONS

Following a standard 12-week course of pharmacotherapy, people with schizophrenia and bipolar disorder were more likely to relapse to smoking without maintenance varenicline treatment. Maintenance pharmacotherapy could improve longer-term tobacco abstinence rates and reduce known smoking-related health disparities in those with SMI.

Unique prediction of cannabis use severity and behaviors by delay discounting and behavioral economic demand

Few studies have simultaneously evaluated delay discounting and behavioral economic demand to determine their unique contribution to drug use. A recent study in cannabis users found that monetary delay discounting uniquely predicted cannabis dependence symptoms, whereas cannabis demand uniquely predicted use frequency. This study sought to replicate and extend this research by evaluating delay discounting and behavioral economic demand measures for multiple commodities and including a use quantity measure. Amazon.com's Mechanical Turk was used to sample individuals reporting recent cannabis use (n=64) and controls (n=72). Participants completed measures of monetary delay discounting as well as alcohol and cannabis delay discounting and demand. Cannabis users and controls did not differ on monetary delay discounting or alcohol delay discounting and demand. Among cannabis users, regression analyses indicated that cannabis delay discounting uniquely predicted use severity, whereas cannabis demand uniquely predicted use frequency and quantity. These effects remained significant after controlling for other delay discounting and demand measures. This research replicates previous outcomes relating delay discounting and demand with cannabis use and extends them by accounting for the contribution of multiple commodities. This research also demonstrates the ability of online crowdsourcing methods to complement traditional human laboratory techniques.

Comparing exponential and exponentiated models of drug demand in cocaine users

Drug purchase tasks provide rapid and efficient measurement of drug demand. Zero values (i.e., prices with zero consumption) present a quantitative challenge when using exponential demand models that exponentiated models may resolve. We aimed to replicate and advance the utility of using an exponentiated model by demonstrating construct validity (i.e., association with real-world drug use) and generalizability across drug commodities. Participants (N = 40 cocaine-using adults) completed Cocaine, Alcohol, and Cigarette Purchase Tasks evaluating hypothetical consumption across changes in price. Exponentiated and exponential models were fit to these data using different treatments of zero consumption values, including retaining zeros or replacing them with 0.1, 0.01, or 0.001. Excellent model fits were observed with the exponentiated model. Means and precision fluctuated with different replacement values when using the exponential model but were consistent for the exponentiated model. The exponentiated model provided the strongest correlation between derived demand intensity (Q0) and self-reported free consumption in all instances (Cocaine r = .88; Alcohol r = .97; Cigarette r = .91). Cocaine demand elasticity was positively correlated with alcohol and cigarette elasticity. Exponentiated parameters were associated with real-world drug use (e.g., weekly cocaine use) whereas these correlations were less consistent for exponential parameters. Our findings show that selection of zero replacement values affects demand parameters and their association with drug-use outcomes when using the exponential model but not the exponentiated model. This work supports the adoption of the exponentiated demand model by replicating improved fit and consistency and demonstrating construct validity and generalizability. (PsycINFO Database Record

Relative reinforcing efficacy of cigarettes as a predictor of smoking abstinence among treatment-seeking smokers

RATIONALE

Relative reinforcing efficacy (RRE) is a core feature of behavioral economic theories of addiction. A measure of RRE in smokers is the cigarette purchase task (CPT). Only one previous study has assessed whether CPT indices predict treatment outcomes among smokers with substance use disorders (SUDs) who were not motivated to quit smoking, limiting the generalizability of the results.

OBJECTIVES

This study was aimed at exploring demand indices as predictors of smoking abstinence among participants receiving a cognitive behavioral treatment (CBT) combined with contingency management (CM) versus CBT alone. It also sought to validate the CPT as a measure of RRE.

METHODS

Participants were 159 (62.3 % women) smokers aged 44.8 (SD 12.6) years randomized to CBT alone or combined with CM. They smoked an average of 21.1 (SD 8.5) cigarettes per day, and their mean score on the Fagerström Test for Nicotine Dependence (FTND) was 5.5 (SD 1.9). Demand indices were generated from a hypothetical CPT assessed at baseline.

RESULTS

Smoking levels were high (≥20 cigarettes) at prices of up to €0.10 per cigarette. Elasticity was the only index that predicted smoking abstinence at the end of treatment, but only in the CBT + CM condition. The variance explained by elasticity was 6.8 % in the independent model and 4.6 % in the covariate model. Cigarette demand indices and smoking-related measures were significantly associated.

CONCLUSION

This is the first research showing that CPT is a valid measure of CM outcome among treatment-seeking smokers. This study also provides evidence of convergent validity for the CPT.

Toward quantifying the abuse liability of ultraviolet tanning: A behavioral economic approach to tanning addiction

Many adults engage in ultraviolet indoor tanning despite evidence of its association with skin cancer. The constellation of behaviors associated with ultraviolet indoor tanning is analogous to that in other behavioral addictions. Despite a growing literature on ultraviolet indoor tanning as an addiction, there remains no consensus on how to identify ultraviolet indoor tanning addictive tendencies. The purpose of the present study was to translate a behavioral economic task more commonly used in substance abuse to quantify the "abuse liability" of ultraviolet indoor tanning, establish construct validity, and determine convergent validity with the most commonly used diagnostic tools for ultraviolet indoor tanning addiction (i.e., mCAGE and mDSM-IV-TR). We conducted a between-groups study using a novel hypothetical Tanning Purchase Task to quantify intensity and elasticity of ultraviolet indoor tanning demand and permit statistical comparisons with the mCAGE and mDSM-IV-TR. Results suggest that behavioral economic demand is related to ultraviolet indoor tanning addiction status and adequately discriminates between potential addicted individuals from nonaddicted individuals. Moreover, we provide evidence that the Tanning Purchase Task renders behavioral economic indicators that are relevant to public health research. The present findings are limited to two ultraviolet indoor tanning addiction tools and a relatively small sample of high-risk ultraviolet indoor tanning users; however, these pilot data demonstrate the potential for behavioral economic assessment tools as diagnostic and research aids in ultraviolet indoor tanning addiction studies.

Persistence and amplitude of cigarette demand in relation to quit intentions and attempts

INTRODUCTION

The cigarette purchase task (CPT) is a method that can be used to assess the relative value of cigarettes. Based on cigarettes purchased across a price range, five derived metrics (Omax, Pmax, breakpoint, intensity, and elasticity) can assess cigarette demand. A study with adolescent smokers found that these could be reduced to two latent factors: persistence (price insensitivity) and amplitude (volumetric consumption). We sought to replicate this structure with adult smokers and examine how these variables relate to cessation efforts.

METHOD

Web-based survey conducted in 2014 among adult (18 years and above) current daily cigarette smokers (N = 1194). Participants completed the CPT, Fagerstrom Test for Nicotine Dependence (FTND), reported past-year quit attempts, and future quit intentions. We included published scales assessing perceived prevalence of smoking, social reactivity, smoker identity, and risk perception.

RESULTS

Our analysis supported two latent variables, persistence and amplitude, which correlated positively with FTND. Persistence was correlated with several psychosocial factors and was higher among those intending to quit very soon, but did not vary by number of past-year quit attempts. Amplitude differed across quit attempts and intention (p < 0.001) and, in multivariable models, was significantly associated with lower 30-day quit intention (OR = 0.76, p = 0.001).

CONCLUSIONS

Persistence and amplitude factors characterized CPT data in adults, discriminated known groups (e.g., smokers by intentions to quit), and were positively associated with nicotine dependence. Factor scores also appear to relate to certain psychosocial factors, such as smoker identity and perceptions of risk. Future research should examine the predictive validity of these constructs.

Nicotine receptor partial agonists for smoking cessation

BACKGROUND

Nicotine receptor partial agonists may help people to stop smoking by a combination of maintaining moderate levels of dopamine to counteract withdrawal symptoms (acting as an agonist) and reducing smoking satisfaction (acting as an antagonist).

OBJECTIVES

To review the efficacy of nicotine receptor partial agonists, including varenicline and cytisine, for smoking cessation.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group's specialised register for trials, using the terms ('cytisine' or 'Tabex' or 'dianicline' or 'varenicline' or 'nicotine receptor partial agonist') in the title or abstract, or as keywords. The register is compiled from searches of MEDLINE, EMBASE, and PsycINFO using MeSH terms and free text to identify controlled trials of interventions for smoking cessation and prevention. We contacted authors of trial reports for additional information where necessary. The latest update of the specialised register was in May 2015, although we have included a few key trials published after this date. We also searched online clinical trials registers.

SELECTION CRITERIA

We included randomised controlled trials which compared the treatment drug with placebo. We also included comparisons with bupropion and nicotine patches where available. We excluded trials which did not report a minimum follow-up period of six months from start of treatment.

DATA COLLECTION AND ANALYSIS

We extracted data on the type of participants, the dose and duration of treatment, the outcome measures, the randomisation procedure, concealment of allocation, and completeness of follow-up.The main outcome measured was abstinence from smoking at longest follow-up. We used the most rigorous definition of abstinence, and preferred biochemically validated rates where they were reported. Where appropriate we pooled risk ratios (RRs), using the Mantel-Haenszel fixed-effect model.

MAIN RESULTS

Two trials of cytisine (937 people) found that more participants taking cytisine stopped smoking compared with placebo at longest follow-up, with a pooled risk ratio (RR) of 3.98 (95% confidence interval (CI) 2.01 to 7.87; low-quality evidence). One recent trial comparing cytisine with NRT in 1310 people found a benefit for cytisine at six months (RR 1.43, 95% CI 1.13 to 1.80).One trial of dianicline (602 people) failed to find evidence that it was effective (RR 1.20, 95% CI 0.82 to 1.75). This drug is no longer in development.We identified 39 trials that tested varenicline, 27 of which contributed to the primary analysis (varenicline versus placebo). Five of these trials also included a bupropion treatment arm. Eight trials compared varenicline with nicotine replacement therapy (NRT). Nine studies tested variations in varenicline dosage, and 13 tested usage in disease-specific subgroups of patients. The included studies covered 25,290 participants, 11,801 of whom used varenicline.The pooled RR for continuous or sustained abstinence at six months or longer for varenicline at standard dosage versus placebo was 2.24 (95% CI 2.06 to 2.43; 27 trials, 12,625 people; high-quality evidence). Varenicline at lower or variable doses was also shown to be effective, with an RR of 2.08 (95% CI 1.56 to 2.78; 4 trials, 1266 people). The pooled RR for varenicline versus bupropion at six months was 1.39 (95% CI 1.25 to 1.54; 5 trials, 5877 people; high-quality evidence). The RR for varenicline versus NRT for abstinence at 24 weeks was 1.25 (95% CI 1.14 to 1.37; 8 trials, 6264 people; moderate-quality evidence). Four trials which tested the use of varenicline beyond the 12-week standard regimen found the drug to be well-tolerated during long-term use. The number needed to treat with varenicline for an additional beneficial outcome, based on the weighted mean control rate, is 11 (95% CI 9 to 13). The most commonly reported adverse effect of varenicline was nausea, which was mostly at mild to moderate levels and usually subsided over time. Our analysis of reported serious adverse events occurring during or after active treatment suggests there may be a 25% increase in the chance of SAEs among people using varenicline (RR 1.25; 95% CI 1.04 to 1.49; 29 trials, 15,370 people; high-quality evidence). These events include comorbidities such as infections, cancers and injuries, and most were considered by the trialists to be unrelated to the treatments. There is also evidence of higher losses to follow-up in the control groups compared with the intervention groups, leading to a likely underascertainment of the true rate of SAEs among the controls. Early concerns about a possible association between varenicline and depressed mood, agitation, and suicidal behaviour or ideation led to the addition of a boxed warning to the labelling in 2008. However, subsequent observational cohort studies and meta-analyses have not confirmed these fears, and the findings of the EAGLES trial do not support a causal link between varenicline and neuropsychiatric disorders, including suicidal ideation and suicidal behaviour. The evidence is not conclusive, however, in people with past or current psychiatric disorders. Concerns have also been raised that varenicline may slightly increase cardiovascular events in people already at increased risk of those illnesses. Current evidence neither supports nor refutes such an association, but we await the findings of the CATS trial, which should establish whether or not this is a valid concern.

AUTHORS' CONCLUSIONS

Cytisine increases the chances of quitting, although absolute quit rates were modest in two recent trials. Varenicline at standard dose increased the chances of successful long-term smoking cessation between two- and three-fold compared with pharmacologically unassisted quit attempts. Lower dose regimens also conferred benefits for cessation, while reducing the incidence of adverse events. More participants quit successfully with varenicline than with bupropion or with NRT. Limited evidence suggests that varenicline may have a role to play in relapse prevention. The most frequently recorded adverse effect of varenicline is nausea, but mostly at mild to moderate levels and tending to subside over time. Early reports of possible links to suicidal ideation and behaviour have not been confirmed by current research.Future trials of cytisine may test extended regimens and more intensive behavioural support.

Current insights into the mechanisms and development of treatments for heavy drinking cigarette smokers

There is a strong association between cigarette smoking and alcohol use at the epidemiological, behavioral, and molecular levels, and this co-use creates substantial impediments to smoking cessation among smokers who are also heavy drinkers. Compared with individuals who only smoke, those who both drink and smoke heavily experience more severe health consequences and have greater difficulty in quitting smoking. During smoking abstinence, greater alcohol use is associated with decreased odds of smoking cessation, and smokers are substantially more likely to experience a smoking lapse during drinking episodes. As heavy drinking smokers are less responsive to the currently available pharmacological treatments, this subgroup of high-risk substance users possesses a unique clinical profile and treatment needs. Thus, treatment development for heavy drinking smokers represents a significant and understudied research area within the field of smoking cessation. This review will briefly describe findings from epidemiological, behavioral, and molecular studies illustrating alcohol and tobacco co-use and identify how the behavioral and neurobiological mechanisms underlying the interaction of alcohol and nicotine may inform the development of targeted treatments for this unique population of smokers.

A modified exponential behavioral economic demand model to better describe consumption data

Behavioral economic demand analyses that quantify the relationship between the consumption of a commodity and its price have proven useful in studying the reinforcing efficacy of many commodities, including drugs of abuse. An exponential equation proposed by Hursh and Silberberg (2008) has proven useful in quantifying the dissociable components of demand intensity and demand elasticity, but is limited as an analysis technique by the inability to correctly analyze consumption values of zero. We examined an exponentiated version of this equation that retains all the beneficial features of the original Hursh and Silberberg equation, but can accommodate consumption values of zero and improves its fit to the data. In Experiment 1, we compared the modified equation with the unmodified equation under different treatments of zero values in cigarette consumption data collected online from 272 participants. We found that the unmodified equation produces different results depending on how zeros are treated, while the exponentiated version incorporates zeros into the analysis, accounts for more variance, and is better able to estimate actual unconstrained consumption as reported by participants. In Experiment 2, we simulated 1,000 datasets with demand parameters known a priori and compared the equation fits. Results indicated that the exponentiated equation was better able to replicate the true values from which the test data were simulated. We conclude that an exponentiated version of the Hursh and Silberberg equation provides better fits to the data, is able to fit all consumption values including zero, and more accurately produces true parameter values.

Risk of neuropsychiatric adverse events associated with varenicline: systematic review and meta-analysis

OBJECTIVE

To determine the risk of neuropsychiatric adverse events associated with use of varenicline compared with placebo in randomised controlled trials.

DESIGN

Systematic review and meta-analysis comparing study effects using two summary estimates in fixed effects models, risk differences, and Peto odds ratios.

DATA SOURCES

Medline, Embase, PsycINFO, the Cochrane Central Register of Controlled Trials (CENTRAL), and clinicaltrials.gov.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomised controlled trials with a placebo comparison group that reported on neuropsychiatric adverse events (depression, suicidal ideation, suicide attempt, suicide, insomnia, sleep disorders, abnormal dreams, somnolence, fatigue, anxiety) and death. Studies that did not involve human participants, did not use the maximum recommended dose of varenicline (1 mg twice daily), and were cross over trials were excluded.

RESULTS

In the 39 randomised controlled trials (10,761 participants), there was no evidence of an increased risk of suicide or attempted suicide (odds ratio 1.67, 95% confidence interval 0.33 to 8.57), suicidal ideation (0.58, 0.28 to 1.20), depression (0.96, 0.75 to 1.22), irritability (0.98, 0.81 to 1.17), aggression (0.91, 0.52 to 1.59), or death (1.05, 0.47 to 2.38) in the varenicline users compared with placebo users. Varenicline was associated with an increased risk of sleep disorders (1.63, 1.29 to 2.07), insomnia (1.56, 1.36 to 1.78), abnormal dreams (2.38, 2.05 to 2.77), and fatigue (1.28, 1.06 to 1.55) but a reduced risk of anxiety (0.75, 0.61 to 0.93). Similar findings were observed when risk differences were reported. There was no evidence for a variation in depression and suicidal ideation by age group, sex, ethnicity, smoking status, presence or absence of psychiatric illness, and type of study sponsor (that is, pharmaceutical industry or other).

CONCLUSIONS

This meta-analysis found no evidence of an increased risk of suicide or attempted suicide, suicidal ideation, depression, or death with varenicline. These findings provide some reassurance for users and prescribers regarding the neuropsychiatric safety of varenicline. There was evidence that varenicline was associated with a higher risk of sleep problems such as insomnia and abnormal dreams. These side effects, however, are already well recognised.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO 2014:CRD42014009224.

Anxiety, depression, and cigarette smoking: a transdiagnostic vulnerability framework to understanding emotion-smoking comorbidity

Research into the comorbidity between emotional psychopathology and cigarette smoking has often focused upon anxiety and depression's manifest symptoms and syndromes, with limited theoretical and clinical advancement. This article presents a novel framework to understanding emotion-smoking comorbidity. We propose that transdiagnostic emotional vulnerabilities-core biobehavioral traits reflecting maladaptive responses to emotional states that underpin multiple types of emotional psychopathology-link various anxiety and depressive psychopathologies to smoking. This framework is applied in a review and synthesis of the empirical literature on 3 transdiagnostic emotional vulnerabilities implicated in smoking: (a) anhedonia (Anh; diminished pleasure/interest in response to rewards), (b) anxiety sensitivity (AS; fear of anxiety-related sensations), and (c) distress tolerance (DT; ability to withstand distressing states). We conclude that Anh, AS, and DT collectively (a) underpin multiple emotional psychopathologies, (b) amplify smoking's anticipated and actual affect-enhancing properties and other mechanisms underlying smoking, (c) promote progression across the smoking trajectory (i.e., initiation, escalation/progression, maintenance, cessation/relapse), and (d) are promising targets for smoking intervention. After existing gaps are identified, an integrative model of transdiagnostic processes linking emotional psychopathology to smoking is proposed. The model's key premise is that Anh amplifies smoking's anticipated and actual pleasure-enhancing effects, AS amplifies smoking's anxiolytic effects, and poor DT amplifies smoking's distress terminating effects. Collectively, these processes augment the reinforcing properties of smoking for individuals with emotional psychopathology to heighten risk of smoking initiation, progression, maintenance, cessation avoidance, and relapse. We conclude by drawing clinical and scientific implications from this framework that may generalize to other comorbidities.

The behavioral economics of substance use disorders: reinforcement pathologies and their repair

The field of behavioral economics has made important inroads into the understanding of substance use disorders through the concept of reinforcer pathology. Reinforcer pathology refers to the joint effects of (a) the persistently high valuation of a reinforcer, broadly defined to include tangible commodities and experiences, and/or (b) the excessive preference for the immediate acquisition or consumption of a commodity despite long-term negative outcomes. From this perspective, reinforcer pathology results from the recursive interactions of endogenous person-level variables and exogenous environment-level factors. The current review describes the basic principles of behavioral economics that are central to reinforcer pathology, the processes that engender reinforcer pathology, and the approaches and procedures that can repair reinforcement pathologies. The overall goal of this review is to present a new understanding of substance use disorders as viewed by recent advances in behavioral economics.

The impact of pre-cessation varenicline on behavioral economic indices of smoking reinforcement

BACKGROUND

Varenicline was developed to aid smoking cessation by reducing smoking reinforcement. The present study tests this reinforcement-reduction hypothesis among smokers preparing to quit.

METHOD

After a one-week baseline, treatment-seeking smokers were randomized to receive three weeks of varenicline or placebo (Weeks 2-4). During each of the four weeks of the study, smokers completed a hypothetical cigarette purchase task (CPT) via handheld devices in their natural environment. Behavioral economic measures of simulated smoking if cigarettes were free (demand intensity), sensitivity of consumption to increasing price (elasticity), and price at which purchases would drop to 0 (breakpoint) were estimated.

RESULTS

The exponential demand equation fit the purchase task data well across subjects and time. As predicted, demand intensity decreased and sensitivity to price (elasticity) increased over time. However, changes in demand intensity did not differ by treatment group. Contrary to our hypothesis that varenicline would increase sensitivity to price, the placebo group tended to become more elastic in their purchases during Weeks 2 and 3; the groups did not differ in elasticity at Week 4. Breakpoint did not vary by group, time, or their interaction.

CONCLUSION

Simulated smoking demand can be validly assessed in the natural environment of treatment-seeking smokers. Simulated demand indices of smoking reinforcement diminished as smokers approached their target quit date. However, there was no evidence that varenicline facilitated these changes over a three-week period, leaving open the mechanisms by which varenicline reduces smoking rate prior to cessation and improves long-term abstinence.

Economic demand predicts addiction-like behavior and therapeutic efficacy of oxytocin in the rat

Development of new treatments for drug addiction will depend on high-throughput screening in animal models. However, an addiction biomarker fit for rapid testing, and useful in both humans and animals, is not currently available. Economic models are promising candidates. They offer a structured quantitative approach to modeling behavior that is mathematically identical across species, and accruing evidence indicates economic-based descriptors of human behavior may be particularly useful biomarkers of addiction severity. However, economic demand has not yet been established as a biomarker of addiction-like behavior in animals, an essential final step in linking animal and human studies of addiction through economic models. We recently developed a mathematical approach for rapidly modeling economic demand in rats trained to self-administer cocaine. We show here that economic demand, as both a spontaneous trait and induced state, predicts addiction-like behavior, including relapse propensity, drug seeking in abstinence, and compulsive (punished) drug taking. These findings confirm economic demand as a biomarker of addiction-like behavior in rats. They also support the view that excessive motivation plays an important role in addiction while extending the idea that drug dependence represents a shift from initially recreational to compulsive drug use. Finally, we found that economic demand for cocaine predicted the efficacy of a promising pharmacotherapy (oxytocin) in attenuating cocaine-seeking behaviors across individuals, demonstrating that economic measures may be used to rapidly identify the clinical utility of prospective addiction treatments.

An open-label pilot trial of N-acetylcysteine and varenicline in adult cigarette smokers

BACKGROUND

Varenicline (VAR) has demonstrated superior efficacy over other smoking cessation pharmacotherapies, though 50-60% of those treated do maintain abstinence. Some preclinical findings suggest that new nicotine dependence pharmacotherapies should target the glutamatergic system, given its demonstrated role in addiction. Attention has been given to N-acetylcysteine (NAC), which appears to restore normal glutamate signaling in animal models. It is possible that NAC and VAR may work in concert to promote abstinence at higher rates than with either medication alone.

OBJECTIVE

To demonstrate the feasibility and safety of co-administering NAC and VAR in nicotine-dependent participants.

METHODS

Participants (n = 19) were daily cigarette smokers, and did not need to be seeking treatment. They received 4 weeks of open-label treatment with NAC (1200 mg twice daily) and VAR (1 mg twice daily, following titration) and were assessed weekly for adverse events (AEs), smoking, craving and withdrawal.

RESULTS

Sixteen participants reported a total of 40 AEs, and most were mild (88%). The most commonly reported AE was nausea (15%). Medication adherence, assessed via self-reports and pill counts, was excellent (98%). Exploratory analyses showed reductions in cigarettes per day, though point prevalence abstinence at the end of the study was low.

CONCLUSIONS

These preliminary data provide the first demonstration of safety and feasibility of the co-administration of NAC and VAR in cigarette smokers. AEs were consistent with those typically reported for VAR and NAC. These data support future efficacy research on NAC and VAR for smoking cessation.

Understanding the effects of stress and alcohol cues on motivation for alcohol via behavioral economics

BACKGROUND

Psychological stress and alcohol cues are common antecedents of both ongoing drinking and relapse. One candidate mechanism of risk from these factors is acute increases in craving, but experimental support for this hypothesis is mixed. Furthermore, the combination of stress and cues has been largely unstudied. The current study employed a behavioral economic approach to investigate the combined roles of psychosocial stress and alcohol cues on motivation for alcohol.

METHODS

In a sample of 84 adult heavy drinkers, we examined the effects of an acute laboratory stress induction and an alcohol cue exposure on subjective craving and stress, arousal, and behavioral economic decision making. Primary dependent measures included an intertemporal cross-commodity multiple-choice procedure (ICCMCP), incorporating both price and delay elements, an alcohol purchase task (APT), measuring alcohol demand, and a monetary delay discounting task, measuring intertemporal choice.

RESULTS

The stress induction significantly increased stress, craving, and the incentive value of alcohol on the ICCMCP and APT. Stress-related increases in value on the ICCMCP were mediated by increased alcohol demand. Exposure to alcohol cues only significantly affected craving, APT breakpoint, and arousal. Delay discounting was not affected by either stress or cues.

CONCLUSIONS

These results reveal unique behavioral economic dimensions of motivation for alcohol following acute stress and an alcohol cue exposure. More broadly, as the first application of this approach to understanding the role of stress in drug motivation, these findings support its utility and potential in future applications.

Involvement of neuronal β2 subunit-containing nicotinic acetylcholine receptors in nicotine reward and withdrawal: implications for pharmacotherapies

WHAT IS KNOWN AND OBJECTIVE

Tobacco smoking remains a major health problem. Nicotine binds to nicotinic acetylcholine receptors (nAChRs), which can cause addiction and withdrawal symptoms upon cessation of nicotine administration. Pharmacotherapies for nicotine addiction target brain alterations that underlie withdrawal symptoms. This review will delineate the involvement of the β2 subunit of neuronal nAChRs in nicotine reward and in generating withdrawal symptoms to better understand the efficacy of smoking cessation pharmacotherapies.

COMMENT

Chronic nicotine desensitizes and upregulates β2 subunit-containing nAChRs, and the prolonged upregulation of receptors may underlie symptoms of withdrawal. Experimental research has demonstrated that the β2 subunit of neuronal nAChRs is necessary for generating nicotine reward and withdrawal symptoms.

WHAT IS NEW AND CONCLUSION

Smoking cessation pharmacotherapies act on β2 subunit-containing nAChRs to reduce nicotine reward and withdrawal symptom severity.