Development and initial validation of a new self-report measure to assess perceived dependence on tobacco and nicotine products

How nicotine is administered has evolved from cigarettes to various delivery systems. Assessing perceived dependence on nicotine-containing products now requires accounting for product specificity while allowing comparisons across products and users. This study aims to develop a new self-report measure to assess perceived dependence on tobacco and nicotine products (TNPs) among exclusive and poly-TNP users. A draft version of the new measure, the ABOUT-Dependence, was constructed based on literature review, qualitative research, and expert opinion. Data for scale formation and psychometric assessment was obtained through a US-based web survey (n = 2334) that included additional dependence measures for convergent validity assessment. Qualitative research confirmed a preliminary conceptual framework with seven sub-concepts. Following a cognitive debriefing, 19 items were considered to best represent the different sub-concepts. Psychometric findings supported a three-domain structure [i.e., behavioral impact (five items), signs and symptoms (five items), and extent/timing of use (two items)] and an overall total composite score. The data confirmed convergent and known-group validity, as well as test-retest reliability. The ABOUT-Dependence is a 12-item, psychometrically sound, self-report measure that may be used as a tool for research and further understanding of perceived dependence across the spectrum of TNP and TNP users.

Nicotinic Receptor Alpha-5 Subunit Gene Polymorphism is Associated with Heavy Smoking Under a Range of Nicotine Dosing Conditions

INTRODUCTION

This study aimed to assess the role of the rs16969968 variant of nicotinic receptor alpha-5 subunit in regulating smoking behavior and nicotine intake in response to nicotine manipulations among dependent smokers in a naturalistic environment.

METHODS

Sixty-nine adults (19 females) smoking 10 or more cigarettes per day were asked to complete four 2-week study phases during which they smoked exclusively one of two types of Spectrum nicotine research cigarettes (FTC nicotine yield 0.8 and 1.6 mg, respectively), their usual brand of cigarettes, or their usual brand of cigarettes while wearing a 21-mg nicotine patch. Measurements included rs16969968 genotype, number of cigarettes per day, smoking topography, and plasma cotinine.

RESULTS

Compared to controls (G/G carriers), A allele carriers reported smoking 4 to 5 more cigarettes per day across all conditions (all ps < .05). Mean total smoke volume per day and cotinine were greater in A allele carriers than in controls (ps = 0.05, 0.046, respectively). No significant genotype differences were found in smoking compensation indices for the switch from Medium to High nicotine yield cigarettes. Nicotine patch-induced reductions in cigarettes smoked per day and total smoke volume per day showed significant interactions between genotype and pre-patch levels, heavier smokers showing greater effects of genotype (p = .052 and p =.006, respectively).

CONCLUSIONS

Results suggest that the rs16969968 variants regulate heaviness of smoking primarily by their impact on daily numbers of cigarettes smoked, but no genotype differences were found in smoking compensation after switching from Medium to High nicotine cigarettes.

IMPLICATIONS

The differences in daily cigarette consumption between rs16969968 risk-allele carriers and controls are shown to be consistent regardless of manipulations of cigarette nicotine content and transdermal nicotine supplementation and markedly greater among dependent smokers than those observed in the general smoker populations. G/G allele carriers, relative to A allele carriers, appeared to be more sensitive to the nicotine patch manipulation, reducing their smoking to a greater extent. These findings support continued efforts in the development of personalized intervention strategies to reduce the rs16969968-conveyed genetic propensity for heavy smoking.

Comparison of brain nicotine accumulation from traditional combustible cigarettes and electronic cigarettes with different formulations

Rapid brain accumulation is critical for the acute reinforcing effects of nicotine. Although nicotine formulation (free-base vs. protonated or salt) in electronic cigarette (E-cig) liquid affects user satisfaction, its impact on brain nicotine accumulation (BNA) from E-cig use has not been evaluated in comparison with traditional combustible cigarettes (C-cigs) using a within-subjects design. BNA was directly assessed with 29 adult dual users (13 females) of E-cigs and C-cigs, using [11C]nicotine and positron emission tomography (PET). Participants underwent two 15-min upper body (from chest to head) scanning sessions during which they inhaled a single puff of [11C]nicotine-labeled vapor from E-cigs with free-base nicotine or C-cig smoke in a randomized order. Seventeen of them also went through another session during which they inhaled from E-cigs with nicotine salt. A full-body scan was also conducted at each session to measure total absorbed dose of [11C]nicotine. Mean maximum nicotine concentration (Cmax) in brain following inhalation of free-base nicotine E-cig vapor was 19% and 15% lower relative to C-cig smoke and nicotine salt E-cig vapor (ps = 0.014 and 0.043, respectively). The Cmax values did not differ significantly between the C-cig and nicotine salt E-cig. Mean values of time to the maximum concentration (Tmax) were not significantly different between the two types of E-cig, but they were 64% and 40% longer than that for C-cig smoking (ps = 0.0005 and 0.004, respectively). Mean Cmax with C-cigs and free-base nicotine E-cigs were greater in females relative to males and correlated with T1/2 of lung nicotine clearance and participants' pack-years. These results suggest that while E-cigs with free-base nicotine formulation can deliver nicotine rapidly to the brain, those with nicotine salt formulation are capable of even more efficient brain nicotine delivery closely resembling combustible cigarettes. Therefore, nicotine formulation or pH in E-liquid should be considered in evaluation of E-cigs in terms of abuse liability and potential in substituting for combustible cigarettes.

Using varenicline in combination with electronic nicotine delivery systems (ENDS)

BACKGROUND

Varenicline is efficacious for smoking cessation, but a return to smokingusually occurs after treatment ends. Electronic nicotine delivery systems (ENDS) may enhance smoking reduction and cessation by providing a behavioral substitute for smoking and may deter smoking in the long term if an individual's nicotine dependence can be transferred to ENDS. The goal of this study was to evaluate varenicline in conjunction with ENDS to promote switching to ENDS.

METHODS

Twenty-five individuals who smoked cigarettes, interested in switching but not seeking cessation treatment, received ENDS for 13 weeks; during weeks 2-13 they received varenicline. Assessments included self-reported cigarette and ENDS use, expired air carbon monoxide (CO), reward ratings, tolerability/side effects, and dependence measures.

RESULTS

Cigarette smoking decreased from 15.6 cigarettes/day (SD=5.6) at baseline to 2.8 cigarettes/day (SD=5.1) at week 13 (paired t(22)=10.24, p<0.0001). 28% of participants were confirmed to be abstinent in the last 4 weeks of treatment. ENDS use remained relatively constant, averaging 11.8 occasions per day (SD=10.6). Cigarette dependence (assessed by time to first use of the day) decreased after introduction of ENDS (paired t(23) = -3.27, p=0.003), and again after the first week of full-dose varenicline (paired t(23) = -4.27, p=0.0003). Dependence on ENDS did not change, starting out lower than cigarettes (paired t(21) = 5.52, p<0.0001), but ending higher (paired t(22) = 2.94, p=0.008). Smoking satisfaction declined markedly, while satisfaction for ENDS remained relatively constant. Treatment tolerability and adherence were high.

CONCLUSIONS

ENDS in combination with varenicline shows promise as a means to reduce dependence on cigarettes and facilitate switching from cigarettes to ENDS.

Adaptive Smoking Cessation Using Precessation Varenicline or Nicotine Patch: A Randomized Clinical Trial

Importance

Adaptive pharmacotherapy, ie, starting a medication regimen and then modifying that regimen based on patient response, is common in many medical domains but is not common in smoking cessation. Recently, studies have found that adaptive treatment using precessation nicotine patches is efficacious for smoking cessation; however, adaptive treatment using precessation varenicline and adaptive treatment in clinical practice settings have not been fully assessed.

Objective

To determine whether adaptive pharmacotherapy leads to higher smoking abstinence rates than standard pharmacotherapy in a clinical practice setting.

Design, Setting, and Participants

This double-blinded stratified placebo-controlled randomized clinical trial compared adaptive treatment with standard treatment for smoking cessation. The study was conducted at a university health system in Durham, North Carolina, from February 2018 to May 2020 and was stopped early due to COVID-19. Data were analyzed as intent-to-treat from May 24, 2021, to February 27, 2022.

Interventions

Participants were allowed to choose varenicline or nicotine patches and were then randomized to adaptive or nonadaptive (standard) treatment. Participants started on their chosen medication (adaptive) or placebo (standard) 4 weeks before their target quit day. Two weeks later, participants were assessed for treatment response. Adaptive participants who did not decrease daily cigarettes smoked by at least 50% (nonresponders) received bupropion in addition to their chosen medication. Participants in the adaptative treatment group who did decrease daily cigarettes smoked by at least 50% (responders) and participants in the standard treatment group received additional placebo bupropion. Participants in the standard treatment group received varenicline starting 1 week before the target quit date or nicotine patches starting on the target quit day. All participants received brief behavioral support.

Main Outcome and Measures

The main outcome was biochemically verified 30-day continuous smoking abstinence 12 weeks after their target quit smoking day. Other measures included demographic characteristics, smoking history, and repeated smoking assessments.

Results

Of the planned 300 participants, a total of 188 participants (mean [SD] age, 49.1 [12.5] years; 102 [54%] female) were enrolled before the trial was stopped because of the COVID-19 pandemic. A total of 127 participants chose to use varenicline, including 64 randomized to adaptive treatment and 63 randomized to standard treatment, and 61 participants chose to use nicotine patches, including 31 randomized to adaptive treatment and 30 randomized to standard treatment. At baseline, participants smoked a mean (SD) of 15.4 (7.3) cigarettes per day. At 12 weeks after the target quit day, biochemically verified 30-day continuous smoking abstinence was observed in 23 of 95 participants (24%) in the adaptive treatment group and 8 of 93 participants (9%) in the standard treatment (odds ratio [OR], 3.38; 95% CI, 1.43-7.99; P = .004); among participants who used varenicline, 30-day continuous abstinence was 18 participants (28%) in the adaptive treatment group, and 5 participants (8%) in the standard treatment group (OR, 4.54; 95% CI, 1.57-13.15); among participants who used nicotine patches, 30-day continuous abstinence was 5 participants (16%) in the adaptive treatment group and 3 participants (10%) in the standard treatment group (OR, 1.73; 95% CI, 0.38-7.99). Sleep problems were more common for participants in the varenicline adaptive treatment group than in the varenicline standard treatment group (rate ratio, 1.74; 95% CI, 1.18-2.58; P = .03).

Conclusions and Relevance

This randomized clinical trial found that adaptive pharmacotherapy was efficacious for smoking cessation treatment in a practice setting.

Trial Registration

ClinicalTrials.gov Identifier: NCT02501265.

Smoking reduction using electronic nicotine delivery systems in combination with nicotine skin patches

RATIONALE

Electronic nicotine delivery systems (ENDS) are used by smokers seeking to reduce combustible cigarette (CC) use, but the role of nicotine replacement vs. behavioral and sensory factors is still poorly understood. We hypothesized that providing nicotine from ENDS in addition to nicotine skin patches would promote smoking reduction relative to non-nicotine control ENDS.

OBJECTIVES

To assess the effects on smoking behavior of using nicotine vs. placebo ENDS in smokers using nicotine vs. placebo patches.

METHODS

Ninety-four daily smokers were enrolled in a study that randomly assigned them to receive ENDS with nicotine vs. without nicotine and skin patches with vs. without nicotine. Smoking reduction and cessation were assessed over an 8-week period by self-report and by expired air carbon monoxide (CO) measurements. The primary outcome was defined as reduction in expired air CO.

RESULTS

The use of nicotine in ENDS led to significant reductions in smoking (ENDS nicotine vs. placebo difference in CO change = -9.2 ppm; 90% CI (-1.5 ppm, -16.9 ppm)) and was highly correlated with reductions in self-reported cigarettes per day (r=0.6). The effect of nicotine in nicotine patches was not statistically significant (patch nicotine vs. placebo difference in CO change = -0.1 ppm; 90% CI (-7.8 ppm, 7.6 ppm)).

CONCLUSIONS

The presence of nicotine in ENDS was associated with a large reduction in smoking. Additional studies will be needed to determine whether there may be additive effects of nicotine ENDS and nicotine patches on smoking abstinence.

Effect of Electronic Cigarette Liquid pH on Retention of 11C-Nicotine in a Respiratory Tract Model

INTRODUCTION

Based on our preliminary 11C-nicotine positron emission tomography (PET) imaging studies in humans, we speculated that greater deposition of nicotine in the respiratory tract from electronic cigarettes compared to combustible cigarettes could result from the alkaline pH of typical aerosol-producing electronic cigarette liquids (e-liquids). To address this hypothesis, we assessed the effect of e-liquid pH on the retention of nicotine in vitro using 11C-nicotine, PET, and a human respiratory tract model of nicotine deposition.

AIMS AND METHODS

A single 2-second 35-mL puff was delivered to a human respiratory tract cast from a 2.8-Ohm cartomizer at 4.1 volts. Immediately after the puff, a 2-second 700-mL air wash-in volume was administered. E-liquids (glycerol and propylene glycol 50/50 vol/vol) containing 24 mg/mL nicotine were mixed with 11C-nicotine. Deposition (retention) of nicotine was assessed using a GE Discovery MI DR PET/CT scanner. Eight e-liquids with different pH values (range 5.3-9.6) were investigated. All experiments were performed at room temperature and at a relative humidity of 70%-80%.

RESULTS

Retention of nicotine in the respiratory tract cast was pH dependent and the pH-sensitive component of the retention was well described by a sigmoid curve. In total, 50% of the maximal pH-dependent effect was observed at pH 8.0, which is close to the pKa2 of nicotine.

CONCLUSIONS

The retention of nicotine in the respiratory tract conducting airways is dependent on the e-liquid pH. Lowering the e-liquid pH reduces retention of nicotine. Nonetheless, reduction of the pH below 7 has little effect, consistent with the pKa2 of protonated nicotine.

IMPLICATIONS

Similar to combustible cigarettes, the retention of nicotine in the human respiratory tract from consumption of electronic cigarettes may have some health consequences and affect nicotine dependence. Here we demonstrated that the retention of nicotine in the respiratory tract is dependent on the e-liquid pH, and lowering pH reduces retention of nicotine in conducting airways of the respiratory tract. Therefore, e-cigarettes with low pH values would result in reduced respiratory tract nicotine exposure and faster delivery of nicotine to the central nervous system (CNS). The latter can be associated with e-cigarette abuse liability and the effectiveness of e-cigarettes as substitutes for combustible cigarettes.

Comparison of brain nicotine uptake from electronic cigarettes and combustible cigarettes

Brain accumulation rate and magnitude are critical for the acute reinforcing effects of nicotine. Despite electronic cigarettes' (E-cigs) appeal as substitutes for traditional combustible cigarettes (C-cigs), brain nicotine accumulation (BNA) from E-cigs has not been compared with that from C-cigs using a within-subjects design. BNA was directly assessed with 16 adult dual users (10 females) of E-cigs (e-liquid pH 9.4) and C-cigs, using 11C-nicotine and positron emission tomography (PET). Participants went through two 15-min head scanning sessions during which they inhaled a single puff of E-cig vapor or C-cig smoke containing 11C-nicotine in a randomized order. A full-body scan was also conducted at each session to measure total absorbed dose of 11C-nicotine. Mean maximum concentration (Cmax) and area under curve of BNA were 22.1% and 22.7% lower, respectively, following E-cig compared with C-cig inhalation. Meanwhile, T1/2 was 2.7 times longer following inhalation of E-cig vapor relative to C-cig smoke (all ps < 0.005). Whole-body imaging indicated greater nicotine retention in the respiratory tract from vapor versus smoke inhalation (p < 0.0001). Following vapor inhalation, nicotine retention in the respiratory tract was correlated with Cmax values of BNA (rs = -0.59, p < 0.02). Our results confirm that E-cigs with alkaline pH e-liquid can deliver nicotine rapidly to the brain, albeit less efficiently than C-cigs partly due to greater airway retention of nicotine. Since brain nicotine uptake mediates reinforcement, these results help elucidate actions of E-cigs in terms of abuse liability and effectiveness in substituting for combustible cigarettes.

Novel rapid-acting sublingual nicotine tablet as a cigarette substitution strategy

RATIONALE

Current nicotine replacement products provide a much slower onset of nicotine delivery than cigarettes, and hence are only marginally effective at supplanting cigarette smoking. Therefore, more effective forms of nicotine replacement are needed.

OBJECTIVES

This initial investigation characterized the pharmacokinetic (PK) and subjective effects of a novel sublingual (SL) nicotine tablet designed to deliver nicotine more rapidly to the bloodstream of smokers.

METHODS

Study 1 (N = 6) characterized the pharmacokinetics of a 2 mg nicotine SL tablet in comparison to an FDA-approved, marketed 2 mg nicotine lozenge. Study 2 (N = 24) assessed subjective responses of smokers to a single use of a 1 mg and 2 mg SL tablet.

RESULTS

Study 1 found that the time to maximum blood nicotine concentrations was significantly shorter for the SL tablet (14 min) than for the lozenge (82 min), and the initial rate of nicotine absorption was higher (0.4 ng/mL*min vs. 0.0 ng/mL*min), supporting the hypothesis that the SL tablet delivered nicotine more rapidly. Study 2 found that participants reported immediate relief of nicotine withdrawal symptoms after tablet administration, and craving reduction after the 2 mg tablet approached the degree reported for their usual brands of cigarettes (4.2 vs. 4.6 on a 7-point scale). Other subjective responses showed the tablet to be an appealing alternative to smoking.

CONCLUSIONS

The novel SL tablet studied shows promise as a nicotine substitution strategy for tobacco harm reduction and smoking cessation treatment. Additional studies are warranted to further investigate the potential of this new approach.

Bupropion/zonisamide combination to assist smokers to switch from combustible cigarettes to electronic nicotine delivery systems (ENDS)

INTRODUCTION

Electronic nicotine delivery systems (ENDS) may offer a much less harmful alternative to combustible cigarettes (CC) for adult smokers unwilling or unable to relinquish nicotine. However, dual use of CC and ENDS undermines potential harm reduction, and progress needs to be made to assist smokers to switch to ENDS. This study explored the promise of a novel treatment combination of the smoking cessation medication bupropion and an FDA-approved anti-seizure medication, zonisamide, to facilitate switching from CC to ENDS. Both medications have been found to reduce craving for CC and possibly offset each other's side effects.

METHODS

Twenty-four smokers participated in a 13-week treatment during which they were provided with ENDS, bupropion and zonisamide. Assessments included CC and ENDS use, expired air carbon monoxide (CO), smoking withdrawal symptoms, reward ratings and tolerability/side effects.

RESULTS

33% of participants achieved biochemically confirmed, complete CC abstinence by the end of treatment. Those who did not achieve complete abstinence nonetheless showed a 44% reduction in expired air CO. Craving and other withdrawal symptoms were minimal, and CC smoking satisfaction declined markedly, while satisfaction ratings for ENDS increased over time to overtake those of CC. Side effects were generally mild, and adherence to the medication use was excellent.

CONCLUSIONS

The use of combination bupropion/zonisamide to facilitate switching from CC to ENDS is a promising approach that merits follow-up randomized controlled trials. Combining short-term medication approaches with long-term nicotine substitution using ENDS may be a promising strategy to help smokers sustain smoking abstinence in the long term.

Self-administration by female rats of low doses of nicotine alone vs. nicotine in tobacco smoke extract

BACKGROUND

Nicotine has reinforcing effects, but there are thousands of other compounds in tobacco, some of which might interact with nicotine reinforcement.

AIMS

This rat study was conducted to determine if nicotine self-administration is altered by co-administration of the complex mixture of compounds in tobacco smoke extract (TSE).

METHODS

Female Sprague-Dawley rats were tested for self-administration of low doses of nicotine (3 or 10 µg/kg/infusion) at three different rates of reinforcement (FR1, FR3 and FR5) over three weeks either alone or together with the complex mixture of tobacco smoke extract (TSE).

RESULTS

Rats self-administering 3 µg/kg/infusion of nicotine alone showed a rapid initiation on an FR1 schedule, but declined with FR5. Rats self-administering nicotine in TSE acquired self-administration more slowly, but increased responding over the course of the study. With 10 µg/kg/infusion rats self-administered significantly more nicotine alone than rats self-administering the same nicotine dose in TSE. Rats self-administering nicotine alone took significantly more infusions with the 10 than the 3 µg/kg/infusion dose, whereas rats self-administering nicotine in TSE did not. Nicotine in TSE led to a significantly greater locomotor hyperactivity at a dose of 0.1 mg/kg compared to rats that received nicotine alone. Rats self-administering nicotine alone had significantly more responding on the active vs. inactive lever, but rats self-administering the same nicotine doses in TSE did not.

CONCLUSIONS

Self-administration of nicotine in a purer form appears to be more clearly discriminated and dose-related than nicotine self-administered in the complex mixture of TSE.

Combination Lorcaserin and Nicotine Patch for Smoking Cessation Without Weight Gain

INTRODUCTION

This study explored the efficacy of combination lorcaserin and nicotine patch for smoking cessation treatment and prevention of postsmoking cessation weight gain.

METHODS

We conducted a trial in which 61 adult daily smokers were asked to quit smoking using a combination of lorcaserin and nicotine patch. During the first 2 weeks of treatment prior to the quit day, participants were randomized to receive either lorcaserin (10 mg twice daily) plus nicotine patch (21 mg) or placebo plus nicotine patch (21 mg). Following this 2-week period, participants received both medications for 12 weeks. Outcomes included 4-week continuous smoking abstinence at the end of treatment (weeks 7-10 postquit attempt), weight change, ad libitum smoking, withdrawal symptoms, and ratings of cigarette reward.

RESULTS

Biochemically confirmed continuous smoking abstinence from 7 to 10 weeks postquit attempt was 31.1% (90% confidence interval, 21.4%-40.8%). Participants who quit smoking showed no weight gain; in fact, mean weight change was minus 0.16 kg (SD = 3.27) over the study period. There was an unexpected but strong association (p = .006) between a decrease in sensory enjoyment of smoking and successful quit outcome on this regimen. During the prequit randomization period, lorcaserin versus placebo reduced the impact of smoking to relieve craving for cigarettes as well as the sensory enjoyment of smoking (p = .005). Adherence and tolerability to lorcaserin and nicotine patch was good.

CONCLUSIONS

The combination of lorcaserin and nicotine patch was well tolerated, associated with a relatively high smoking abstinence rate, and effectively prevented weight gain associated with quitting smoking.

IMPLICATIONS

This report provides an important contribution to the literature because it details evidence of a medication combination-lorcaserin and nicotine-that is effective for smoking cessation and for ameliorating weight gain associated with smoking cessation. For many smokers, postcessation weight gain is a major obstacle to quitting, and this medication combination provides a suitable treatment option for these smokers.

CLINICAL TRIAL REGISTRATION

NCT02906644.

Overcoming barriers to disseminate effective smoking cessation treatments globally

Purpose

The purpose of this paper is to review the barriers in the dissemination of effective smoking cessation treatments and services globally. Offering tobacco users help to stop using tobacco is a key demand reduction measure outlined under Article 14 of the World Health Organisation (WHO) Framework Convention on Tobacco Control (FCTC). Implementing Article 14 can reap great dividends for the billion plus tobacco users around the world and their families, friends and societies.

Design/methodology/approach

A review of the status of the global implementation of Article 14 using available literature on smoking cessation products, services and national guidelines. Discussing innovative approaches being currently explored in South Asia that can lead to faster adoption and implementation of Article 14 globally.

Findings

Major gaps remain in cessation products’ availability and resource allocation for cessation services globally. Current licensed products are falling short on delivering and sustaining smoking cessation. Innovation in cessation products and services needs to build on learnings in nicotine pharmacokinetics, behavioural insights from consumer research and tap into 21st century tools such as mobile based apps. National implementation of FCTC’s Article 14 needs to follow guidelines that encourage integration into existing health programmes and health-care practitioners’ (HCPs) upskilling.

Originality/value

Smoking cessation is a desirable health outcome and nicotine replacement products are a means of achieving cessation through tobacco harm reduction. E-cigarettes are sophisticated nicotine replacement products. Innovation is urgently needed to fill the gaps in smoking cessation products and services, and for converting global policy into local practice. In low- and middle-income countries (LMICs), HCPs’ knowledge, attitudes and practice regarding tobacco use and cessation may hold the key to rapidly scaling up cessation support and delivery to achieve FCTC objectives sooner. Additionally, HCPs can play an important role in offering smoking cessation support in existing national health programmes for TB, cancer screening and maternal and child health. Also, widely prevalent smartphone devices may deliver smoking cessation through telemedicine in LMICs sooner, leapfrogging the hurdles of the existing health-care infrastructure.

Prolonging the Reduction of Nicotine Self-Administration in Rats by Coadministering Chronic Nicotine With Amitifadine, a Triple Monoamine Reuptake Inhibitor With CYP2B6 Inhibitory Actions

INTRODUCTION

Existing treatments can aid tobacco smoking cessation, but they have low efficacy. Because there is a network of neural systems involved in tobacco addiction, combination treatments may provide greater efficacy. Chronic nicotine and amitifadine have each been shown to significantly reduce nicotine self-administration in rats. This study was conducted to determine if the combination of chronic nicotine with amitifadine, a triple monoamine reuptake inhibitor with CYP2B inhibitory effects, would reduce nicotine self-administration to a greater extent than either alone or placebo.

METHODS

This study tested the combination of nicotine plus amitifadine in young adult female Sprague-Dawley rats self-administering nicotine (0.03 mg/kg/infusion). This combination was compared with each treatment alone and the vehicle during continuing nicotine self-administration as well as during resumption of self-administration after a week of enforced abstinence, modeling a quit attempt. Finally, we studied the residual effects of these therapies after discontinuation of treatment.

RESULTS

Treatment with either chronic nicotine or amitifadine alone significantly reduced nicotine self-administration relative to controls. The combination of the treatments significantly enhanced this effect. After treatment withdrawal, all of the groups showed increases in nicotine self-administration, but only the combined treatment group remained significantly below control rates of nicotine self-administration.

CONCLUSIONS

This study showed the promise of amitifadine as a possible new treatment for smoking cessation and suggested that amitifadine is more effective when given with chronic nicotine. The improved efficacy of the amitifadine and nicotine combination may be potentiated by amitifadine's inhibitory effects on CYP2B, which slows nicotine metabolism.

IMPLICATIONS

This study replicated the effects that chronic nicotine or chronic amitifadine, a triple reuptake inhibitor, significantly reduces nicotine self-administration in rats. It extends those findings by showing that the combination of chronic nicotine plus amitifadine causes significantly greater reduction in nicotine self-administration than either drug treatment alone. The combination of chronic amitifadine and chronic nicotine also causes a persistent significant reduction in nicotine self-administration after the end of treatment. The amitifadine and nicotine treatment should be assessed in humans to determine whether this combination provides greater efficacy in smoking cessation than transdermal nicotine treatment alone.

Rapid Brain Nicotine Uptake from Electronic Cigarettes

This study sought to determine brain nicotine kinetics from use of the increasingly popular electronic cigarette (E-cig). Methods: In 17 E-cig users (9 men and 8 women), brain uptake of nicotine after inhalation from E-cigs was directly assessed using ¹¹C-nicotine PET. The brain nicotine kinetics were compared with those from smoking combustible cigarettes (C-cigs). Results: A single puff of E-cig vapor caused the nicotine concentration in the brain to rise quickly (mean time to reach 50% of maximum brain nicotine concentration, 27 s), with a peak amplitude 25% higher in women than men, resembling previous observations with C-cigs. Nonetheless, the accumulation from E-cigs (24%) was less than that from C-cigs (32%) in both men and women. Conclusion: E-cigs can deliver nicotine to the brain with a rapidity similar to that of C-cigs. Therefore, to the extent that rapid brain uptake promotes smoking reward, E-cigs might maintain a degree of nicotine dependence and also serve as a noncombustible substitute for cigarettes.

Chronic memantine decreases nicotine self-administration in rats

Neurobehavioral bases of tobacco addiction and nicotine reinforcement are complex, involving more than only nicotinic cholinergic or dopaminergic systems. Memantine is an NMDA glutamate antagonist used to improve cognitive function in people with Alzheimer's disease. Glutamate may be an important component of the reinforcing effects of nicotine, so memantine was evaluated as a potential smoking cessation aid. Two studies were conducted with adult female rats, one testing acute effects of memantine over a range of doses for changing nicotine self-administration and the other testing the chronic effects of memantine to reduce nicotine self-administration. Acute memantine injections slightly, but significantly, increased nicotine self-administration in a dose-related manner. In contrast, chronic memantine treatment significantly reduced nicotine self-administration. During the first day of memantine administration in the chronic study, nicotine self-administration was significantly elevated replicating the acute study. Starting in the second week of treatment there was a significant reduction of nicotine self-administration relative to controls. This was seen because memantine treatment prevented the increase in nicotine self-administration shown by controls. There even continued to be a memantine-induced lowered nicotine self-administration during the week after the cessation of memantine treatment. Memantine or other drugs affecting NMDA glutamate receptors may be useful aids to smoking cessation. Full efficacy for reducing nicotine self-administration was seen as the NMDA drug treatment is given chronically. Importantly, the effect persisted even after treatment is ended, indicating the high potential for NMDA glutamate receptors to impact nicotine addiction.

GABAergic Neurons as Putative Neurochemical Substrate Mediating Aversive Effects of Nicotine

Nicotine, the main addictive component of tobacco smoke, has both rewarding and aversive properties. Recent studies have suggested that GABAergic neurons, one of the main neurochemical components of the reward-addiction circuitry, may also play a role in the aversive responses to nicotine. In the present study of transgenic mice expressing Green Fluorescent Protein (GFP) in Glutamate Decarboxylase 67 (GAD67) neurons, we hypothesized that a subpopulation of GABAergic neurons in the Ventral Tegmental Area (VTA) are the targets of aversive doses of nicotine in the CNS. We tested this hypothesis using c-Fos immunohistochemical techniques to identify GAD67-GFP positive cells within the VTA, that are activated by a single intraperitoneal (i.p.) injection of a low (40 ug/kg) or a high (2 mg/kg) dose of nicotine. We also assessed the anatomical location of GAD67-GFP positive cells with respect to tyrosine hydroxylase (TH) Immunoreactive (IR) dopaminergic cells in VTA. Consistent with our previous studies low- and high-dose nicotine both induced c-Fos activation of various intensities at multiple sites in VTA. Double labeling of c-Fos activated cells with GAD67-GFP positive cells identified a subpopulation of GABAergic neurons in Substantia Nigra Compact part Medial tier (SNCM) that were activated by high- but not by low-dose nicotine. Of 217 GABAergic cells counted at this site, 48.9% exhibited nicotine induced c-fos immunoreactivity. GAD67-GFP positive cells in other regions of VTA were not activated by the nicotine doses tested. Double labeling of GAD67-GFP positive cells with TH IR cells showed that the GABAergic neurons that were activated by high-dose nicotine were located in close proximity to the dopaminergic neurons of substantia nigra compact part and VTA. Dose-dependent activation of GAD67-GFP positive neurons in SNCM, by a nicotine dose known to produce aversive responses, implies that GABAergic neurons at these sites may be an important component of the nicotine aversive circuitry.

Lorcaserin for Smoking Cessation and Associated Weight Gain: A Randomized 12-Week Clinical Trial

Introduction

Lorcaserin is a selective serotonin 2C receptor agonist approved by the Food and Drug Administration for chronic weight management. Preclinical data suggest that it may also be effective in smoking cessation through modulation of the dopaminergic reward system.

Methods

This was a 12-week, randomized, double-blind, placebo-controlled trial conducted in 30 centers in the United States. Six hundred three adult smokers with a Body Mass Index of 18.5-35 kg/m2, averaging at least 10 cigarettes/day with no period of abstinence >3 months for the past year were randomized to lorcaserin 10 mg once daily (QD), 10 mg twice daily (BID) or placebo; all received standardized smoking cessation counseling weekly. The target quit date was day 15. The primary endpoint was the exhaled carbon monoxide confirmed Continuous Abstinence Rate for weeks 9-12 (month 3).

Results

Continuous Abstinence Rates for month 3 were 5.6%, 8.7%, and 15.3% for the placebo, QD and BID groups, respectively (BID vs. placebo odds ratio 3.02, 95% confidence interval 1.47, 6.22, p = .0027. Change in weight at week 12 (randomized population) was -0.01, -0.35 and -0.98 kg, respectively (p = .0004, BID vs. placebo), and +0.73, +0.76, and -0.41 kg in participants achieving month 3 continuous abstinence. The most frequent adverse events were headache, nausea, constipation, and fatigue.

Conclusions

Lorcaserin with counseling was associated with dose-related increases in smoking cessation and prevention of associated weight gain over a 3-month period. Further investigation of lorcaserin in smoking cessation is warranted. Trial Registration: ClinicalTrials.gov. Identifier: NCT02044874.

Implications

This randomized, controlled trial demonstrated that lorcaserin used in conjunction with standard cessation counseling was associated with dose-related increases in smoking cessation and prevention of associated weight gain. To our knowledge, this is the first demonstration in humans of a potential role of 5-HT2C agonism in the modulation of central neurological circuits involved with reward.

Combination Varenicline/Bupropion Treatment Benefits Highly Dependent Smokers in an Adaptive Smoking Cessation Paradigm

Introduction

This study replicated and extended results of a previous trial, which found that combination varenicline/bupropion treatment increased smoking abstinence in smokers who were male, highly dependent, and who did not respond to prequit nicotine patch treatment with a >50% reduction in expired-air carbon monoxide in the first week.

Methods

One hundred and twenty-two male nicotine patch nonresponders and 52 responders were identified. Smokers in each group were randomized to receive 12 weeks of varenicline plus bupropion treatment versus varenicline plus placebo. The primary outcome was continuous smoking abstinence at weeks 8–11 after the target quit date.

Results

For smokers with a high level of dependence, judged by having a baseline Fagerstrom Test for Nicotine Dependence (FTND) score ≥ 6 and cigarette consumption ≥ 20/d, combination varenicline/bupropion treatment increased the abstinence rate relative to varenicline alone: 71.0% versus 43.8% (odds ratio = 3.14; 95% confidence interval = 1.11–8.92, p [one tailed] = .016). In contrast, less dependent smokers did not show a benefit of combination treatment relative to varenicline (abstinence rates of 32.1% vs. 45.6%, respectively); there was a significant interaction of treatment and dependence level. Patch nonresponders tended to benefit the most from combination treatment, which was well tolerated overall.

Conclusions

Combination varenicline/bupropion treatment proved significantly more efficacious than varenicline alone among highly dependent male smokers. These results, together with prior studies, support an adaptive treatment paradigm that assigns smoking cessation treatment according to baseline smoker characteristics and initial response to nicotine patch treatment.

Implications

This study replicated, in a prospective manner, an important and surprising retrospective finding from a previous clinical trial, which showed that a specific subpopulation of smokers benefited substantially from receiving a combination treatment of varenicline plus bupropion, relative to varenicline plus placebo. Specifically, male smokers having high baseline nicotine dependence (FTND score ≥ 6 and cigarette consumption ≥ 20/d), showed a marked increase in smoking abstinence rate on combination pharmacotherapy. The present study likewise found an enhancement in end-of-treatment abstinence rate in this subgroup, from 43.8% to 71.0%. The adaptive treatment paradigm, which classifies smokers based on initial dependence level and response to prequit nicotine patch treatment, may be used to identify target populations of smokers whose success can be enhanced by intervening with combination pharmacotherapy before the quit-smoking date.

Trial Registration

ClinicalTrials.gov identifier: NCT01806779.

Neuroanatomical Relationships between Orexin/Hypocretin-Containing Neurons/Nerve Fibers and Nicotine-Induced c-Fos-Activated Cells of the Reward-Addiction Neurocircuitry

Orexin/hypocretin-containing neurons in lateral hypothalamus (LH) are implicated in the neurobiology of nicotine addiction. However, the neuroanatomical relationships between orexin-neurons/nerve fibers and nicotine-activated cells within the reward-addiction neurocircuitry is not known. In the present study in mice, we first used c-Fos immunohistochemistry to identify CNS cells stimulated by an acute single injection of nicotine (NIC, 2 mg/kg, IP). Sequential double-labelling was then performed to identify the location of orexin-containing neurons and nerve fibers with respect to NIC-induced c-Fos activated cells and/or tyrosine hydroxylase (TH) immunoreactive (IR) cells of the mesocorticolimbic reward-addiction pathways. Orexin-IR nerve fibers and terminals were detected at multiple sites of the NIC reward-addiction circuitry in close apposition to, and intermingled with, NIC-induced c-Fos-IR cells of locus coeruleus (LC), ventral tegmental area (VTA), nucleus accumbens (Acb), LH and paraventricular thalamic nucleus (PVT). Double-labelling of orexin with TH showed frequent contact between orexin-IR nerve fibers and noradrenergic cells of LC. However, there was infrequent contact between the orexinergic fibers and the TH-expressing dopaminergic cells of VTA, dorsal raphe nucleus (DR), posterior hypothalamus (DA11), arcuate hypothalamic nucleus (DA12) and periventricular areas (DA14). The close anatomical contact between orexinergic nerve fibers and NIC-activated cells at multiple sites of the reward-addiction pathways suggests that orexinergic projections from LH are likely to be involved in modulating activity of the neurons that are directly impacted by acute administration of nicotine.

A programmable smoke delivery device for PET imaging with cigarettes containing 11C-nicotine

INTRODUCTION

PET imaging with ¹¹C-nicotine-loaded cigarettes is a valuable tool to directly assess fast nicotine kinetics and its neuropharmacological role in tobacco dependence. To eliminate variations among puffs inhaled by subjects, this work aimed to develop a programmable smoke delivery device (SDD) to produce highly reproducible and adjustable puffs of cigarette smoke for PET experiments.

NEW METHOD

The SDD was built around a programmable syringe pump as a smoking machine to draw a puff of smoke from a ¹¹C-nicotine-loaded cigarette and make it available for a subject to take the smoke into the mouth and then inhale it during PET data acquisition. Brain nicotine time activity curves and total body absorbed ¹¹C-nicotine doses (TAD) were measured in smokers who inhaled a single puff of smoke via the SDD from a ¹¹C-nicotine-loaded cigarette.

RESULTS

Nearly identical brain nicotine kinetics were observed between participants who inhaled a puff of smoke through the SDD and those who inhaled directly from a cigarette.

COMPARISON WITH EXISTING METHODS

This new device minimizes puff variations that exist with earlier smoke delivery apparatuses which could introduce confounding factors.

CONCLUSIONS

The SDD is effective in delivering ¹¹C-nicotine from the study cigarettes. Despite a 2-s increase in aging of smoke delivered through the SDD versus smoke taken directly from a cigarette, the difference in brain nicotine kinetics after ¹¹C-nicotine delivery with and without use of the SDD is negligible. This refined device may be useful for future research on the deposition and pharmacokinetics of nicotine inhaled with tobacco smoke.

Reduction of nicotine self-administration by chronic nicotine infusion with H1 histamine blockade in female rats

RATIONALE

Chronic nicotine infusion via transdermal patches has been widely shown to assist with smoking cessation. In particular, transdermal nicotine treatment prior to quitting smoking helps reduce ad libitum smoking and aids cessation Rose et al. (Nicotine Tob Res 11:1067-75, 2009). However, despite this success, the majority of smokers who use transdermal nicotine fail to permanently quit smoking. Additional treatments are needed. Tobacco addiction does not just depend on nicotinic receptor systems; a variety of neural systems are involved, including dopamine, norepinepherine, serotonin, and histamine.

OBJECTIVES

Given the involvement of a variety of neural systems in the circuits of addiction, combination therapy may offer improved efficacy for successful smoking cessation beyond single treatments alone. We have found that pyrilamine, an H1 histamine antagonist, significantly decreases nicotine self-administration in rats.

METHODS

The current study was conducted to confirm the effect of chronic nicotine infusion on ongoing nicotine self-administration and resumed access after enforced abstinence and to determine the interaction of chronic nicotine with an H1 antagonist treatment.

RESULTS

Chronic nicotine infusion via osmotic minipump (2.5 and 5 mg/kg/day for 28 days) significantly reduced nicotine self-administration in a dose-dependent manner. Chronic nicotine infusion also reduced the resumption of nicotine self-administration after enforced abstinence. Chronic pyrilamine infusion (25 mg/kg/day for 14 days) also significantly reduced nicotine self-administration.

CONCLUSION

The combination of chronic nicotine and pyrilamine reduced nicotine self-administration to a greater extent than treatment with either drug alone.

The effects of nicotine and non-nicotine smoking factors on working memory and associated brain function

Smoking abstinence impairs executive function, which may promote continued smoking behavior and relapse. The differential influence of nicotine and non-nicotine (i.e. sensory, motor) smoking factors and related neural substrates is not known. In a fully factorial, within-subjects design, 33 smokers underwent fMRI scanning following 24 hours of wearing a nicotine or placebo patch while smoking very low nicotine content cigarettes or remaining abstinent from smoking. During scanning, blood oxygenation level-dependent (BOLD) signal was acquired while participants performed a verbal N-back task. Following 24-hour placebo (versus nicotine) administration, accuracy on the N-back task was significantly worse and task-related BOLD signal lower in dorsomedial frontal cortex. These effects were observed irrespective of smoking. Our data provide novel evidence that abstinence-induced deficits in working memory and changes in underlying brain function are due in large part to abstinence from nicotine compared with non-nicotine factors. This work has implications both for designing interventions that target abstinence-induced cognitive deficits and for nicotine-reduction policy.

The Sensory Impact of Nicotine on Noradrenergic and Dopaminergic Neurons of the Nicotine Reward - Addiction Neurocircuitry

The sensory experience of smoking is a key component of nicotine addiction known to result, in part, from stimulation of nicotinic acetylcholine receptors (nAChRs) at peripheral sensory nerve endings. Such stimulation of nAChRs is followed by activation of neurons at multiple sites in the mesocorticolimbic reward pathways. However, the neurochemical profiles of CNS cells that mediate the peripheral sensory impact of nicotine remain unknown. In the present study in mice, we first used c-Fos immunohistochemistry to identify CNS cells stimulated by nicotine (NIC, 40 μg/kg, IP) and by a peripherally-acting analog of nicotine, nicotine pyrrolidine methiodide (NIC-PM, 30 μg/kg, IP). Sequential double-labelling was then performed to determine whether noradrenergic and dopaminergic neurons of the nicotine reward-addiction circuitry were primary targets of NIC and NIC-PM. Double-labelling of NIC and/or NIC-PM activated c-Fos immunoreactive cells with tyrosine hydroxylase (TH) showed no apparent c-Fos expression by the dopaminergic cells of the ventral tegmental area (VTA). With the exception of sparse numbers of TH immunoreactive D11 cells, dopamine-containing neurons in other areas of the reward-addiction circuitry, namely periaqueductal gray, and dorsal raphe, were also devoid of c-Fos immunoreactivity. Noradrenergic neurons of locus coeruleus (LC), known to innervate VTA, were activated by both NIC and NIC-PM. These results demonstrate that noradrenergic neurons of LC are among the first structures that are stimulated by single acute IP injection of NIC and NIC-PM. Dopaminergic neurons of VTA and other CNS sites, did not respond to acute IP administration of NIC or NIC-PM by induction of c-Fos.

Dextromethorphan interactions with histaminergic and serotonergic treatments to reduce nicotine self-administration in rats

Combining effective treatments with diverse mechanisms of action for smoking cessation may provide better therapy by targeting multiple points of control in the neural circuits underlying addiction. Previous research in a rat model has shown that dextromethorphan, which has α3β4 nicotinic and NMDA glutamatergic antagonist actions, significantly decreases nicotine self-administration. We have found in the rat model that the H1 histamine antagonist pyrilamine and the serotonin 5HT2C agonist lorcaserin also significantly reduce nicotine self-administration. The current studies were conducted to determine the interactive effects of dextromethorphan with pyrilamine and lorcaserin on nicotine self-administration in rats. Young adult female rats were fitted with jugular IV catheters and trained to self-administer a nicotine infusion dose of 0.03-mg/kg/infusion. In an initial dose-effect function study of dextromethorphan, we found a monotonic decrease in nicotine self-administration over a dose range of 1 to 30-mg/kg with the lowest effective dose of 3-mg/kg. Then, with two separate cohorts of rats, dextromethorphan (0, 3.3, and 10-mg/kg) interactions with pyrilamine (0, 4.43, and 13.3-mg/kg) were investigated as well as interactions with lorcaserin (0, 0.3125 and 0.625-mg/kg). In the pyrilamine-dextromethorphan interaction study, an acute dose of pyrilamine (13.3-mg/kg) as well as an acute dose of dextromethorphan caused a significant decrease in nicotine self-administration. There were mutually augmenting effects of these two drugs. The combination of dextromethorphan (10-mg/kg) and pyrilamine (13.3-mg/kg) significantly lowered nicotine self-administration relative to either 10-mg/kg of dextromethorphan alone (p<0.05) or 13.3-mg/kg of pyrilamine alone (p<0.0005). In the lorcaserin-dextromethorphan study, an acute dose of lorcaserin (0.312-mg/kg) as well as an acute dose of dextromethorphan (10-mg/kg) caused a significant decrease in nicotine self-administration replicating previous findings. Augmenting interactions were observed with dextromethorphan and pyrilamine as well as lorcaserin. These findings suggest that combination therapy may be more effective smoking cessation treatments than monotherapy.

Amitifadine, a triple monoamine re-uptake inhibitor, reduces nicotine self-administration in female rats

A wider diversity of drug treatments to aid smoking cessation is needed to help tailor the most efficacious treatment for different types of smokers. This study was conducted to determine whether amitifadine, which inhibits re-uptake of dopamine, norepinephrine and serotonin, would decrease nicotine self-administration at doses that do not cause adverse side effects. Adult female Sprague-Dawley rats were trained to self-administer nicotine intravenous (IV) and were given acute doses of amitifadine in a repeated measures counterbalanced design. Effects of amitifadine on locomotor activity and food motivated responding were also evaluated. Chronic amitifadine effects were also examined. The 30 mg/kg amitifadine dose significantly reduced nicotine self-administration. The 5 and 10 mg/kg doses reduced nicotine self-administration during the first 15 min of the session when the greatest amount of nicotine was self-administered. The 30 mg/kg amitifadine dose, but not the lower doses caused a significant reduction in locomotor activity averaged over the one-hour session and reduced food motivated responding. The 10 mg/kg dose caused hypoactivity at the beginning of the session, but 5 mg/kg did not cause any hypoactivity. The effects of chronic amitifadine treatment (10 mg/kg) over the course of 15 sessions was also determined. Amitifadine caused a significant reduction in nicotine self-administration, which was not seen to diminish over two consecutive weeks of treatment and a week after enforced abstinence. Amitifadine significantly reduced nicotine self-administration. This prompts further research to determine if amitifadine might be an effective treatment for smoking cessation.

Bupropion-varenicline interactions and nicotine self-administration behavior in rats

Varenicline and bupropion each have been shown to significantly improve cessation of tobacco addiction in humans. They act through different mechanisms and the question about the potential added efficacy with their combined used has arisen. Preclinical animal models of nicotine addiction can help with the evaluation of this combined approach and what dose combinations of varenicline and bupropion may be useful for enhancing tobacco cessation. In this study, we investigated the interacting dose-effect functions of varenicline and bupropion in a rat model of nicotine self-administration. Young adult female Sprague-Dawley rats were allowed to self-administer nicotine in 1-h sessions under an FR1 reinforcement schedule. Varenicline (0.3, 1. 3 mg/kg) and bupropion (8.33, 25, 75 mg/kg) were administered alone or together 15 min before each session. The vehicle saline was the control. Higher doses of each drug alone reduced nicotine self-administration compared to control with reductions of 62% and 75% with 3 mg/kg varenicline and 75 mg/kg bupropion respectively. Lower dose varenicline which does not by itself reduce nicotine self-administration, significantly augmented bupropion effects. The 0.3 mg/kg varenicline dose combined with the 25 and 75 mg/kg bupropion doses caused greater reductions of nicotine self-administration than either dose of bupropion given alone. However, higher dose varenicline did not have this effect. Lower dose bupropion did not augment varenicline effects. Only the high bupropion dose significantly enhanced the varenicline effect. Likewise, combining 1 mg/kg varenicline with 75 mg/kg bupropion reduced self-administration to a greater extent than either dose alone. These results demonstrate that combination therapy with varenicline and bupropion may be more beneficial than monotherapy with either drug alone.

Nicotine and non-nicotine smoking factors differentially modulate craving, withdrawal and cerebral blood flow as measured with arterial spin labeling

Smoking cessation results in withdrawal symptoms such as craving and negative mood that may contribute to lapse and relapse. Little is known regarding whether these symptoms are associated with the nicotine or non-nicotine components of cigarette smoke. Using arterial spin labeling, we measured resting-state cerebral blood flow (CBF) in 29 adult smokers across four conditions: (1) nicotine patch+denicotinized cigarette smoking, (2) nicotine patch+abstinence from smoking, (3) placebo patch+denicotinized cigarette smoking, and (4) placebo patch+abstinence from smoking. We found that changes in self-reported craving positively correlated with changes in CBF from the denicotinized cigarette smoking conditions to the abstinent conditions. These correlations were found in several regions throughout the brain. Self-reported craving also increased from the nicotine to the placebo conditions, but had a minimal relationship with changes in CBF. The results of this study suggest that the non-nicotine components of cigarette smoke significantly impact withdrawal symptoms and associated brain areas, independently of the effects of nicotine. As such, the effects of non-nicotine factors are important to consider in the design and development of smoking cessation interventions and tobacco regulation.

Combination treatment with varenicline and bupropion in an adaptive smoking cessation paradigm

OBJECTIVE

The authors assessed the efficacy and safety of combination treatment with varenicline and sustained-release bupropion for smokers who, based on an assessment of initial smoking reduction prior to the quit date, were deemed unlikely to achieve abstinence using nicotine patch treatment.

METHOD

In a randomized, double-blind, parallel-group adaptive treatment trial, the authors identified 222 cigarette smokers who failed to show a reduction of more than 50% in smoking after 1 week of nicotine patch treatment. Smokers were randomly assigned to receive 12 weeks of varenicline plus bupropion or varenicline plus placebo. The primary outcome measure was continuous smoking abstinence at weeks 8-11 after the target quit date.

RESULTS

Both treatments were well tolerated. Participants who received the combination treatment had a significantly higher abstinence rate than those who received varenicline plus placebo (39.8% compared with 25.9%; odds ratio=1.89; 95% CI=1.07, 3.35). Combination treatment had a significantly greater effect on abstinence rate in male smokers (odds ratio=4.26; 95% CI=1.73, 10.49) than in female smokers (odds ratio=0.94; 95% CI=0.43, 2.05). It also had a significantly greater effect in highly nicotine-dependent smokers (odds ratio=3.51, 95% CI=1.64, 7.51) than in smokers with lower levels of dependence (odds ratio=0.71, 95% CI=0.28, 1.80).

CONCLUSIONS

Among smokers who did not show a sufficient initial response to prequit nicotine patch treatment, combination treatment with varenicline and bupropion proved more efficacious than varenicline alone for male smokers and for smokers with a high degree of nicotine dependence.

NIH electronic cigarette workshop: developing a research agenda

BACKGROUND

Electronic cigarettes (e-cigarettes) represent an emerging public health issue. These devices deliver nicotine along with other constituents, including flavorants, via an inhalable aerosol. Their uptake is rapidly increasing in both adults and youths, primarily among current smokers. Public debate is increasing on how these devices should be regulated and used, yet only limited peer-reviewed research exists. To develop a informed policy for e-cigarettes, their effects on human behavior, physiology, and health need to be understood.

PURPOSE

This paper describes proceedings from a National Institutes of Health-sponsored workshop, which was held in November 2013, to identify research needs related to the effects of e-cigarettes. Discussion topics included e-cigarette risks and abuse potential; the potential role for e-cigarettes in harm reduction and smoking cessation; unintended consequences of e-cigarette use, such as becoming a gateway to conventional cigarettes; and dual use of both e-cigarettes and conventional cigarettes.

RESULTS AND CONCLUSIONS

The research needs identified by the workshop participants included the following: standards to measure the contents and emissions of e-cigarettes; biomarkers of exposure; physiological effects of e-cigarettes on tissues and organ systems, including pulmonary and cardiovascular; information on e-cigarette users, how the devices are used, and identification of the best tools to assess these measures; factors that drive use and influence patterns of use; and appropriate methods for evaluating a potential role for e-cigarettes in smoking or nicotine cessation. To understand fully the challenges and the opportunities that e-cigarettes represent, expertise will be needed in basic, behavioral, translational, and clinical sciences.

IV nicotine self-administration in rats using a consummatory operant licking response: sensitivity to serotonergic, glutaminergic and histaminergic drugs

Tobacco smoking is characterized by repeated self-administration of nicotine by placing the cigarette in the mouth. The repeated hand-to-mouth self-administration is essentially a consummatory act. We recently developed a paradigm in which rats lick one of two spouts to trigger intravenous (IV) delivery of nicotine, which combines a consummatory act with rapid delivery of nicotine to model the act of tobacco smoking. We have found that rats will lick hundreds of times per nicotine infusion. In the current study, using the operant licking nicotine self-administration model with young adult Sprague-Dawley rats (0.03mg/kg/infusion of nicotine), we tested the effect of antagonists of H1 histamine receptors pyrilamine, serotonin (5HT) type 2 receptors ketanserin and N-methyl-d-aspartate (NMDA) glutamate receptors with d-cycloserine as well as an agonist of 5HT2c receptors lorcaserin, in dose ranges that we have found in previous studies to significantly reduce IV nicotine self-administration with the operant lever press operand. The H1 antagonist pyrilamine significantly reduced operant licking for nicotine self-administration. Pyrilamine caused significant reductions in the operant licking paradigm at lower doses (10 and 20mg/kg) than those we previously observed to affect responding in the operant lever press paradigm. In contrast, the 5HT2A and C antagonist ketanserin did not show an effect of reducing nicotine self-administration in the same dose range we had found in a previous study to significantly reduce operant lever press nicotine self-administration. The 5HT2C agonist lorcaserin significantly decreased nicotine self-administration in the licking paradigm at the same dose threshold as with lever press responding. The NMDA glutamate partial agonist d-cycloserine did not produce any change in nicotine self-administration with the licking operand, in contrast to its effect on the classic lever-pressing task. The rat model incorporating consummatory aspects of tobacco addiction can provide distinct and potentially more relevant information concerning possible new avenues of treatment to combat tobacco addiction.

Neuroanatomical circuitry mediating the sensory impact of nicotine in the central nervous system

Direct actions of nicotine in the CNS appear to be essential for its reinforcing properties. However, activation of nicotinic acetylcholine receptors (nAChRs) on afferent sensory nerve fibers is an important component of addiction to, and withdrawal from, cigarette smoking. The aim of the present study was to identify the neuroanatomical substrates activated by the peripheral actions of nicotine and to determine whether these sites overlap brain structures stimulated by direct actions of nicotine. Mouse brains were examined by immunohistochemistry for c-Fos protein after intraperitoneal injection of either nicotine hydrogen tartrate salt (NIC; 30 and 40 μg/kg) or nicotine pyrrolidine methiodide (NIC-PM; 20 and 30 μg/kg). NIC-PM induced c-Fos immunoreactivity (IR) at multiple brain sites. In the brainstem, c-Fos IR was detected in the locus coeruleus, laterodorsal tegmental nucleus, and pedunculotegmental nucleus. In the midbrain, c-Fos IR was observed in areas overlapping the ventral tegmental area (VTA), which includes the paranigral nucleus, parainterfascicular nucleus, parabrachial pigmental area, and rostral VTA. Other structures of the nicotine brain-reward circuitry activated by NIC-PM included the hypothalamus, paraventricular thalamic nucleus, lateral habenular nucleus, hippocampus, amygdala, accumbens nucleus, piriform cortex, angular insular cortex, anterior olfactory nucleus, lateral septal nucleus, bed nucleus of stria terminalis, cingulate and medial prefrontal cortex, olfactory tubercle, and medial and lateral orbital cortex. NIC, acting through central and peripheral nAChRs, produced c-Fos IR in areas that overlapped NIC-PM-induced c-Fos-expressing sites. These neuroanatomical data are the first to demonstrate that the CNS structures that are the direct targets of nicotine are also anatomical substrates for the peripheral sensory impact of nicotine.

Brain nicotinic acetylcholine receptor availability and response to smoking cessation treatment: a randomized trial

IMPORTANCE

Cigarette smoking leads to upregulation of nicotinic acetylcholine receptors (nAChRs) in the human brain, including the common α4β2* nAChR subtype. While subjective aspects of tobacco dependence have been extensively examined as predictors of quitting smoking with treatment, no studies to our knowledge have yet reported the relationship between the extent of pretreatment upregulation of nAChRs and smoking cessation.

OBJECTIVE

To determine whether the degree of nAChR upregulation in smokers predicts quitting with a standard course of treatment.

DESIGN, SETTING, AND PARTICIPANTS

Eighty-one tobacco-dependent cigarette smokers (volunteer sample) underwent positron emission tomographic (PET) scanning of the brain with the radiotracer 2-FA followed by 10 weeks of double-blind, placebo-controlled treatment with nicotine patch (random assignment). Pretreatment specific binding volume of distribution (VS/fP) on PET images (a value that is proportional to α4β2* nAChR availability) was determined for 8 brain regions of interest, and participant-reported ratings of nicotine dependence, craving, and self-efficacy were collected. Relationships between these pretreatment measures, treatment type, and outcome were then determined. The study took place at academic PET and clinical research centers.

MAIN OUTCOMES AND MEASURES

Posttreatment quit status after treatment, defined as a participant report of 7 or more days of continuous abstinence and an exhaled carbon monoxide level of 3 ppm or less.

RESULTS

Smokers with lower pretreatment VS/fP values (a potential marker of less severe nAChR upregulation) across all brain regions studied were more likely to quit smoking (multivariate analysis of covariance, F8,69 = 4.5; P < .001), regardless of treatment group assignment. Furthermore, pretreatment average VS/fP values provided additional predictive power for likelihood of quitting beyond the self-report measures (stepwise binary logistic regression, likelihood ratio χ21 = 19.8; P < .001).

CONCLUSIONS AND RELEVANCE

Smokers with less upregulation of available α4β2* nAChRs have a greater likelihood of quitting with treatment than smokers with more upregulation. In addition, the biological marker studied here provided additional predictive power beyond subjectively rated measures known to be associated with smoking cessation outcome. While the costly, time-consuming PET procedure used here is not likely to be used clinically, simpler methods for examining α4β2* nAChR upregulation could be tested and applied in the future to help determine which smokers need more intensive and/or lengthier treatment.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01526005.

Differential effects of non-nicotine tobacco constituent compounds on nicotine self-administration in rats

Tobacco smoking has been shown to be quite addictive in people. However, nicotine itself is a weak reinforcer compared to other commonly abused drugs, leading speculation that other factors contribute to the high prevalence of tobacco addiction in the human population. In addition to nicotine, there are over 5000 chemical compounds that have been identified in tobacco smoke, and more work is needed to ascertain their potential contributions to tobacco's highly addictive properties, or as potential candidates for smoking cessation treatment. In this study, we examined seven non-nicotine tobacco constituent compounds (anabasine, anatabine, nornicotine, myosmine, harmane, norharmane, and tyramine) for their effects on nicotine self-administration behavior in rats. Young adult female Sprague-Dawley rats were allowed to self-administer nicotine (0.03 mg/kg/50 μl infusion) under a fixed ratio-1 schedule of reinforcement. Each self-administration session lasted 45 min. Doses of each tobacco constituent compound were administered subcutaneously 10 min prior to the start of each session in a repeated measures, counterbalanced order two times. Anabasine displayed a biphasic dose-effect function. Pretreatment with 0.02 mg/kg anabasine resulted in a 25% increase in nicotine self-administration, while 2.0mg/kg of anabasine reduced nicotine infusions per session by over 50%. Pretreatment with 2.0mg/kg anatabine also significantly reduced nicotine self-administration by nearly half. These results suggest that some non-nicotine tobacco constituents may enhance or reduce nicotine's reinforcing properties. Also, depending upon the appropriate dose, some of these compounds may also serve as potential smoking cessation agents.

Smoking quit success genotype score predicts quit success and distinct patterns of developmental involvement with common addictive substances

Genotype scores that predict relevant clinical outcomes may detect other disease features and help direct prevention efforts. We report data that validate a previously established v1.0 smoking cessation quit success genotype score and describe striking differences in the score in individuals who display differing developmental trajectories of use of common addictive substances. In a cessation study, v1.0 genotype scores predicted ability to quit with P=0.00056 and area under receiver-operating characteristic curve 0.66. About 43% vs 13% quit in the upper vs lower genotype score terciles. Latent class growth analyses of a developmentally assessed sample identified three latent classes based on substance use. Higher v1.0 scores were associated with (a) higher probabilities of participant membership in a latent class that displayed low use of common addictive substances during adolescence (P=0.0004) and (b) lower probabilities of membership in a class that reported escalating use (P=0.001). These results indicate that: (a) we have identified genetic predictors of smoking cessation success, (b) genetic influences on quit success overlap with those that influence the rate at which addictive substance use is taken up during adolescence and (c) individuals at genetic risk for both escalating use of addictive substances and poor abilities to quit may provide especially urgent focus for prevention efforts.

Role of insular cortex D₁ and D₂ dopamine receptors in nicotine self-administration in rats

The insular cortex has been associated with the processing of rewarding stimuli and with the neural bases of drug addiction. Ischemic damage to the insula has been associated with decreased desire to smoke cigarettes. Which component of insular function is involved in the neural basis of cigarette smoking is not clear. Dopamine systems are crucial for the reinforcing value of addictive drugs. The DA projection from the ventral tegmental area to the nucleus accumbens (NAc) has been shown to be a vital pathway for the primary reinforcement caused by taking a variety of abused drugs. In the current set of studies, the roles of D₁ and D₂ receptors in the insular cortex in the self-administration of nicotine by rats were assessed. Adult female Sprague-Dawley rats were fitted with jugular catheters and given access to self-administer nicotine. Bilateral local infusion cannulae were implanted into the agranular insular cortex to locally administer D₁ and D₂ antagonists (SCH-23390 and haloperidol). Acute local infusions of the D₁ antagonist SCH-23390 into the insula (1-2 μg/side) significantly decreased nicotine self-administration by more than 50%. Repeated infusions of SCH-23390 into the agranular insula caused continuing decreases in nicotine self-administration without signs of tolerance. In contrast, local infusions of the D₂ antagonist haloperidol 0.5-2 μg/side did not have any discernable effect on nicotine self-administration. These studies show the importance of DA D₁ systems in the insula for nicotine reward.

Adapting smoking cessation treatment according to initial response to precessation nicotine patch

OBJECTIVE The authors evaluated an adaptive smoking cessation treatment strategy in which nicotine patch treatment was initiated before a quit date, and then, depending on initial therapeutic response, either the nicotine patch was continued or alternative pharmacotherapies were provided. METHOD The study was a double-blind, parallel-arm adaptive treatment trial. A total of 606 cigarette smokers started open-label nicotine patch treatment 2 weeks before the quit date. Those whose ad lib smoking did not decrease by &gt;50% after 1 week were randomly assigned to one of three double-blind treatments: nicotine patch alone (control condition); "rescue" treatment with bupropion augmentation of the patch; or rescue treatment with varenicline alone. Participants whose precessation smoking decreased &gt;50% but who lapsed after the quit date were also randomly assigned to the two rescue treatments or to nicotine patch alone. Logistic regression analyses compared each rescue treatment against the control condition in terms of abstinence at the end of treatment (weeks 8-11) and at 6 months. RESULTS Smokers who did not respond adequately to precessation nicotine patch benefited from bupropion augmentation; abstinence rates at end of treatment were 16% with nicotine patch alone and 28% with bupropion augmentation (odds ratio=2.04, 95% CI=1.03-4.01). Switching to varenicline produced less robust effects, but point abstinence at 6 months was 6.6% with the patch alone and 16.5% with a switch to varenicline (odds ratio=2.80, 95% CI=1.11-7.06). Postquit adaptive changes in treatment had no significant effects on any abstinence outcome. CONCLUSIONS It is possible to rescue a significant portion of smokers who would have failed to achieve abstinence if left on nicotine patch alone by identifying these smokers before their quit date and implementing adaptive changes in treatment.

Biomarkers for smoking cessation

One way to enhance therapeutic development is through the identification and development of evaluative tools such as biomarkers. This review focuses on putative diagnostic, pharmacodynamic, and predictive biomarkers for smoking cessation. These types of biomarkers may be used to more accurately diagnose a disease, personalize treatment, identify novel targets for drug discovery, and enhance the efficiency of drug development. Promising biomarkers are presented across a range of approaches including metabolism, genetics, and neuroimaging. A preclinical viewpoint is also offered, as are analytical considerations and a regulatory perspective summarizing a pathway toward biomarker qualification.

Repetitive transcranial magnetic stimulation of the superior frontal gyrus modulates craving for cigarettes

BACKGROUND

Previous functional magnetic resonance imaging studies have shown strong correlations between cue-elicited craving for cigarettes and activation of the superior frontal gyrus (SFG). Repetitive transcranial magnetic stimulation (rTMS) offers a noninvasive means to reversibly affect brain cortical activity, which can be applied to testing hypotheses about the causal role of SFG in modulating craving.

METHODS

Fifteen volunteer smokers were recruited to investigate the effects of rTMS on subjective responses to smoking versus neutral cues and to controlled presentations of cigarette smoke. On different days, participants were exposed to three conditions: 1) high-frequency (10 Hz) rTMS directed at the SFG; 2) low-frequency (1 Hz) rTMS directed at the SFG; and 3) low-frequency (1 Hz) rTMS directed at the motor cortex (control condition).

RESULTS

Craving ratings in response to smoking versus neutral cues were differentially affected by the 10-Hz versus 1-Hz SFG condition. Craving after smoking cue presentations was elevated in the 10-Hz SFG condition, whereas craving after neutral cue presentations was reduced. Upon smoking in the 10-Hz SFG condition, ratings of immediate craving reduction as well as the intensity of interoceptive airway sensations were also attenuated.

CONCLUSIONS

These results support the view that the SFG plays a role in modulating craving reactivity; moreover, the results suggest that the SFG plays a role in both excitatory and inhibitory influences on craving, consistent with prior research demonstrating the role of the prefrontal cortex in the elicitation as well as inhibition of drug-seeking behaviors.

Menthol preference among smokers: association with TRPA1 variants

INTRODUCTION

Preference for smoking menthol cigarettes differs from individual to individual and population to population in ways that may provide higher levels of nicotine intake and contribute to smoking's morbidity and mortality. Menthol acts at sites that include the transient receptor potential (TRP) A1 channel that is expressed by nociceptors in the lung and airways, suggesting that individual and population differences in TRPA1 sequences might contribute to observed differences in menthol preference among smokers.

METHODS

We have thus sought association between menthol preference and common variants in the TRPA1 gene in heavier and lighter European-American smokers. Smokers were recruited for studies of smoking cessation in North Carolina and of substance abuse genetics in Maryland.

RESULTS

A common TRPA1 haplotype is defined by 1 missense and 10 intronic single nucleotide polymorphisms that display significant (.006 < p < .05; χ(2)) association with preference for mentholated cigarettes in heavy smokers (odds ratio ca. 1.3). There are smaller trends in the same direction in lighter smokers.

CONCLUSIONS

This TRPA1 haplotype provides a novel biological basis for individual differences in menthol preference and possibly for actions of other agents that act at TRPA1.

Lorcaserin, a 5-HT2C agonist, decreases nicotine self-administration in female rats

Lorcaserin, a selective 5-hydroxytryptamine(2C) (5-HT(2C)) agonist, has been shown to facilitate weight loss in obese populations. It was assessed for its efficacy in reducing nicotine self-administration in young adult female Sprague-Dawley rats. The effect of short-term doses (subcutaneous) on nicotine self-administration (0.03 mg/kg per infusion) with a fixed ratio 1 schedule was assessed in 3-h sessions. Short-term lorcaserin doses (0.3125-20 mg/kg) were administered in a counterbalanced order. Significant reduction of nicotine self-administration was achieved with all of the short-term doses in this range. Tests of lorcaserin on locomotor activity detected prominent sedative effects at doses greater than 1.25 mg/kg with more modest transient effects seen at 0.625 to 1.25 mg/kg. Long-term effects of lorcaserin on locomotor activity were tested with repeated injections with 0.625 mg/kg lorcaserin 10 times over 2 weeks. This low lorcaserin dose did not cause an overall change in locomotor activity relative to that of saline-injected controls. Long-term lorcaserin (0.625 mg/kg) significantly reduced nicotine self-administration over a 2-week period of repeated injections. Long-term lorcaserin at this same dose had no significant effects on food self-administration over the same 2-week period of repeated injections. These studies support development of the 5-HT(2C) agonist lorcaserin to aid tobacco smoking cessation.

Silver acetate interactions with nicotine and non-nicotine smoke components

Oral topical silver-containing formulations were marketed in the 1970s and 1980s as smoking deterrents, based on the finding that when using such formulations, an unpleasant taste occurs upon smoking. This approach has not been widely adopted, however, in part because of a lack of efficacy data. The advent of new pharmacologic treatments for smoking cessation renews the possibility that such a taste aversion approach may be a useful adjunct to smoking cessation treatment. This study explored the basic mechanistic question of whether topical oral silver acetate solution interacts with nicotine as opposed to non-nicotine smoke constituents. We recruited 20 smoking volunteers to rate nicotine-containing or denicotinized cigarettes, as well as the Nicotrol nicotine vapor inhaler and sham (air) puffs. In two sessions, subjects rated the sensory and hedonic qualities of puffs after rinsing their mouths with either silver acetate solution or deionized water (placebo). Silver acetate relative to placebo solution substantially reduced liking and satisfaction ratings for the usual brand and denicotinized cigarettes; in contrast, for the nicotine inhaler these ratings were unaffected by the silver-based treatment. These results support the conclusion that silver acetate not only renders the taste of cigarette smoke less appealing, but also that the compound appears to interact selectively with non-nicotine smoke constituents. Moreover, these data suggest silver acetate would be compatible with buccal nicotine delivery systems (e.g., nicotine lozenge or gum). Combined use of taste aversion with nicotine replacement therapy could provide the smoker with additional assistance to resist relapse. Further exploration is warranted of the use of silver-based preparations as a short-term adjunct to smoking cessation treatment.

Genome-wide association for smoking cessation success in a trial of precessation nicotine replacement

Abilities to successfully quit smoking display substantial evidence for heritability in classic and molecular genetic studies. Genome-wide association (GWA) studies have demonstrated single-nucleotide polymorphisms (SNPs) and haplotypes that distinguish successful quitters from individuals who were unable to quit smoking in clinical trial participants and in community samples. Many of the subjects in these clinical trial samples were aided by nicotine replacement therapy (NRT). We now report novel GWA results from participants in a clinical trial that sought dose/response relationships for "precessation" NRT. In this trial, 369 European-American smokers were randomized to 21 or 42 mg NRT, initiated 2 wks before target quit dates. Ten-week continuous smoking abstinence was assessed on the basis of self-reports and carbon monoxide levels. SNP genotyping used Affymetrix 6.0 arrays. GWA results for smoking cessation success provided no P value that reached "genome-wide" significance. Compared with chance, these results do identify (a) more clustering of nominally positive results within small genomic regions, (b) more overlap between these genomic regions and those identified in six prior successful smoking cessation GWA studies and (c) sets of genes that fall into gene ontology categories that appear to be biologically relevant. The 1,000 SNPs with the strongest associations form a plausible Bayesian network; no such network is formed by randomly selected sets of SNPs. The data provide independent support, based on individual genotyping, for many loci previously nominated on the basis of data from genotyping in pooled DNA samples. These results provide further support for the idea that aid for smoking cessation may be personalized on the basis of genetic predictors of outcome.