Do former smokers respond to nicotine differently from never smokers? A pilot study

A study of pyrazines in cigarettes and how additives might be used to enhance tobacco addiction

BACKGROUND

Nicotine is known as the drug that is responsible for the addicted behaviour of tobacco users, but it has poor reinforcing effects when administered alone. Tobacco product design features enhance abuse liability by (A) optimising the dynamic delivery of nicotine to central nervous system receptors, and affecting smokers' withdrawal symptoms, mood and behaviour; and (B) effecting conditioned learning, through sensory cues, including aroma, touch and visual stimulation, to create perceptions of pending nicotine reward. This study examines the use of additives called 'pyrazines', which may enhance abuse potential, their introduction in 'lights' and subsequently in the highly market successful Marlboro Lights (Gold) cigarettes and eventually many major brands.

METHODS

We conducted internal tobacco industry research using online databases in conjunction with published scientific literature research, based on an iterative feedback process.

RESULTS

Tobacco manufacturers developed the use of a range of compounds, including pyrazines, in order to enhance 'light' cigarette products' acceptance and sales. Pyrazines with chemosensory and pharmacological effects were incorporated in the first 'full-flavour, low-tar' product achieving high market success. Such additives may enhance dependence by helping to optimise nicotine delivery and dosing and through cueing and learned behaviour.

CONCLUSIONS

Cigarette additives and ingredients with chemosensory effects that promote addiction by acting synergistically with nicotine, increasing product appeal, easing smoking initiation, discouraging cessation or promoting relapse should be regulated by the US Food and Drug Administration. Current models of tobacco abuse liability could be revised to include more explicit roles with regard to non-nicotine constituents that enhance abuse potential.

Nicotine reinforcement in never-smokers

RATIONALE

Global tobacco-related mortality dwarfs that of all other drugs. Nicotine is believed to be the primary agent responsible for tobacco use and addiction. However, nicotine is a relatively weak and inconsistent reinforcer in nonhumans and nicotine reinforcement has not been demonstrated in never-smokers.

OBJECTIVES

This study investigated the discriminative, subjective, and reinforcing effects of nicotine in never-smokers.

METHODS

Eighteen never-smokers (< 50 lifetime nicotine exposures) participated in a double-blind study. During a drug discrimination phase, volunteers ingested oral nicotine and placebo capsules (quasi-random order) at least 2 h apart and rated subjective effects repeatedly for 2 h after ingestion in daily sessions. Blocks of 10 sessions were continued until significant discrimination was achieved (p ≤ 0.05, binomial test; ≥ 8 of 10). Following discrimination, nicotine choice was tested by having volunteers choose which capsule set to ingest on each daily session. Successive blocks of 10 sessions were conducted until choice for nicotine or placebo met significance within each volunteer (≥ 8 of 10 sessions).

RESULTS

All 18 volunteers significantly discriminated nicotine from placebo; the lowest dose discriminated ranged from 1.0 to 4.0 mg/70 kg. Nine volunteers significantly chose nicotine (choosers) and nine significantly chose placebo (nicotine avoiders). The choosers reported predominately positive nicotine subjective effects (e.g., alert/attentive, good effects, liking), while avoiders tended to report negative effects (e.g., dizzy, upset stomach, disliking). Both choosers and avoiders attributed their choice to the qualitative nature of drug effects.

CONCLUSIONS

These results provide the first evidence that nicotine can function as a reinforcer in some never-smokers.

New terminology for the treatment of tobacco dependence: a proposal for debate

Tobacco dependence is characterised as a chronic, relapsing disorder that typically requires multiple quit attempts before successful, long-term abstinence is achieved (Steinberg, Foulds, Richardson, Burke, & Shah, 2006). Best practice, evidence-based treatment includes multiple-session counselling and pharmacotherapy, or the combination of both (Fiore et al., 2008). The field has moved past the notion that tobacco dependence is simply a bad habit, a vice, or a moral deficiency that can be overcome by willpower or education alone (Mars & Ling, 2008). However, the language used in discussing treatment has not always been consistent with this evidence. Some words and phrases used lend themselves to varied meanings, and could lead to significant misunderstanding not only among professionals in the field, but also among the general public (O'Brien, 2010; Davis, 1992; Perkins, 1999; Hughes, 2013). In this paper, we discuss some commonly used, problematic terminology, and suggest more appropriate terms (Table 1).

Effects of cannabis use status on cognitive function, in males with schizophrenia

Cognitive impairment and cannabis use are common among patients with schizophrenia. However, the moderating role of cannabis on cognition remains unclear. We sought to examine cognitive performance as a function of cannabis use patterns in schizophrenia. A secondary aim was to determine the effects of cumulative cannabis exposure on cognition. Cognition was assessed in male outpatients with current cannabis dependence (n=18) and no current cannabis use disorders (n=29). We then parsed non-current users into patients with lifetime cannabis dependence (n=21) and no lifetime cannabis dependence (n=8). Finally, as an exploratory analysis, we examined relationships between cumulative cannabis exposure and cognition in lifetime dependent patients. Cross-sectional comparisons suggest that lifetime cannabis users demonstrate better processing speed than patients with no lifetime dependence. Exploratory analyses indicated that patients with current dependence exhibited robust negative relationships between cumulative cannabis exposure and cognition; these associations were absent in former users. Cannabis status has minimal effects on cognition in males with schizophrenia. However, cumulative cannabis exposure significantly impairs cognition in current, but not former users, suggesting that the state dependent negative effects of cannabis may be reversed with sustained abstinence. Prospective studies are needed to confirm these findings.

Neuropsychological performance in patients with schizophrenia and controls as a function of cigarette smoking status

Schizophrenia is associated with many neurocognitive deficits, some of which are improved by nicotine and cigarette smoking. To better understand the relationship between smoking and cognitive function in schizophrenia, cross-sectional assessment of neuropsychological performance as a function of smoking status (smoker or non-smoker) and smoking history (current, former or never-smoker) in clinically stable outpatients with schizophrenia and controls was evaluated. Subjects (n=140) were divided into subgroups on the basis of self-report and biochemical verification of smoking history. Current smokers with schizophrenia (n=38), former smokers with schizophrenia (n=17), never-smokers with schizophrenia (n=12), control smokers (n=31), control former smokers (n=16), and control never-smokers (n=26) were administered a comprehensive neuropsychological battery. Smokers were studied under non-deprivation conditions. Comparison of neuropsychological performance in schizophrenia and control subjects revealed significant main effects of diagnosis. Analysis of the data as a function of smoking history demonstrated that never-smokers with schizophrenia performed the poorest on measures of sustained attention, processing speed and response inhibition, when compared to the other schizophrenia subgroups. Cigarette smoking did not alter neuropsychological performance in controls. Our findings suggest that smoking status and history differentially alters neuropsychological outcomes in schizophrenia compared to non-psychiatric controls, and that never-smokers may present with more severe neurocognitive impairments.

Electrophysiological evidence of nicotine's distracter-filtering properties in non-smokers

Nicotine-enhanced attentional functions are purported to underlie improvements in behavioral performance in cognitive tasks but it is unclear as to whether these effects involve selective attention or attentional control under conditions of distraction. Behavioral and event-related potential measures were used to examine the effects of nicotine on distractibility in 21 non-smokers who were instructed to ignore task-irrelevant auditory stimuli while they performed a visual discrimination task. In a randomized, double-blind, placebo-controlled cross-over design, nicotine gum (6 mg) shortened overall reaction times but failed to prevent increased response slowing and errors caused by deviant sounds. Relative to placebo, nicotine did not modulate the early pre-attentive detection of deviants as reflected in the mismatch negativity but it attenuated the amplitude of the deviant-elicited P3a, an event-related potential component indexing the involuntary shifting of attention. Nicotine also enhanced attentional re-focusing back on to task-relevant stimuli following distraction as evidenced by an increased amplitude of the re-orienting negativity. These findings and the behavioral-electrophysiological dissociation seen with nicotine are discussed in relation to theories of attention and smoking motivation.

Effects of bupropion on simulated demand for cigarettes and the subjective effects of smoking

INTRODUCTION

The biobehavioral mechanism(s) mediating bupropion's efficacy are not well understood. Behavioral economic measures such as demand curves have proven useful in investigations of the reinforcing effects of drugs of abuse. Behavioral economic measures may also be used to measure the effect of pharmacotherapies on the reinforcing effects of drugs of abuse.

METHODS

The effects of bupropion on simulated demand for cigarettes were investigated in a placebo-controlled double-blind clinical trial. Participants reported the number of cigarettes they would purchase and consume in a single day at a range of prices. The effects of medication on the subjective effects of smoking were also explored.

RESULTS

Demand for cigarettes was well described by an exponential demand equation. Bupropion did not significantly decrease the maximum number of cigarettes that participants said they would smoke in a single day nor did it significantly alter the relation between price per cigarette and demand. Baseline demand elasticity did not predict smoking cessation, but changes in elasticity following 1 week of treatment did. Medication group had no effect on any subjective effects of smoking.

DISCUSSION

Bupropion had no significant effects on demand for cigarettes. The exponential demand equation, recently introduced in behavioral economics, proved amenable to human simulated demand and might be usefully employed in other pharmacotherapy studies as it provides a potentially useful measure of changes in the essential value of the drug as a reinforcer. Such changes may be useful in predicting the efficacy of medications designed to reduce drug consumption.

Self-administration of intravenous nicotine in male and female cigarette smokers

Although nicotine is the main addictive chemical in tobacco, there have been few studies of pure nicotine self-administration in humans. The goal of this study was to test the parameters of an intravenous (IV) nicotine self-administration model using nicotine doses presumed to be within the range of those of average intake from cigarette smoking. Six male and four female smokers participated in a double-blind, placebo-controlled, crossover study, which consisted of one adaptation and three experimental sessions. In each experimental session, subjects were randomly assigned to one of the three doses of nicotine (0.1, 0.4, or 0.7 mg). The lowest nicotine dose, 0.1 mg, was chosen to be approximately half the amount of nicotine inhaled from one puff of a cigarette. During each experimental session, subjects first sampled the assigned nicotine dose and placebo and then had the opportunity to choose between nicotine and placebo for a total of six choices over a 90-min period. Out of six options, the average (SEM) number of nicotine choices were 3.0 (0.48) for 0.1 mg, 4.7 (0.48) for 0.4 mg and 4.5 (0.46) for 0.7 mg, indicating a significant effect of nicotine dose on nicotine choice. Both the 0.4 and 0.7, but not the 0.1 mg, nicotine doses were preferred to placebo. These higher doses also produced increases in heart rate, blood pressure, and ratings of drug liking and high. Overall, these findings indicate that smokers chose both the 0.4 and the 0.7 mg nicotine doses over placebo. Our model may be useful in the evaluation of the effects of both behavioral and pharmacological manipulations on nicotine self-administration in humans.

The effects of nicotine on attention and working memory in never-smokers

The subjective and physiological effects of nicotine in nicotine-naive individuals are consistent across studies, though the cognitive effects are variable: Positive, negative, or no effects have been reported. Assessing specific cognitive processes (e.g., alerting, orienting, executive function, and phonological and visuospatial working memory) may help reduce this variability. This within-subject study (N = 20) was designed to assess the effect of nicotine gum (0, 2, or 4 mg) on subjective, physiological, and cognitive measures. Dose-dependent increases in dysphoria and heart rate were observed, though nicotine did not influence any aspect of attention or working memory. Future studies should take into account the difference in effect sizes for cognitive versus physiological/subjective measures and maximize power (e.g., increase sample size) accordingly.

Does nicotine do what we think it does? A meta-analytic review of the subjective effects of nicotine in nasal spray and intravenous studies with smokers and nonsmokers

We conducted a meta-analysis of placebo-controlled laboratory studies of the subjective effects of nicotine. A total of 15 studies (11 with nasal spray, four with intravenous administration) with smokers and six studies (all with nasal spray) with never-smokers were included. Studies of other routes of administration (e.g., smoked tobacco) were not included because of insufficient numbers of available effect sizes. Meta-analysis results indicated that nicotine increased vigor for smokers but increased fatigue for never-smokers. Nicotine increased head rush for both smokers and never-smokers. In studies of smokers only, nicotine also increased ratings of drug high and drug liking. Contrary to expectations, nicotine decreased relaxation and increased tension/jitteriness for both smokers and never-smokers. Dose-response relationships were most clearly observed for head rush and drug high. Considerable variability was found across studies for a given nicotine dose and route of administration. Implications of the current findings about the role of subjective effects in nicotine reinforcement and self-administration are discussed along with commentary on methodological issues and recommendations for future studies.

Transdermal nicotine maintenance attenuates the subjective and reinforcing effects of intravenous nicotine, but not cocaine or caffeine, in cigarette-smoking stimulant abusers

The effects of transdermal nicotine maintenance on the subjective, reinforcing, and cardiovascular effects of intravenously administered cocaine, caffeine, and nicotine were examined using double-blind procedures in nine volunteers with histories of using tobacco, caffeine, and cocaine. Each participant was exposed to two chronic drug maintenance phases (21 mg/day nicotine transdermal patch and placebo transdermal patch). Within each drug phase, the participant received intravenous injections of placebo, cocaine (15 and 30 mg/70 kg), caffeine (200 and 400 mg/70 kg), and nicotine (1.0 and 2.0 mg/70 kg) in mixed order across days. Subjective and cardiovascular data were collected before and repeatedly after drug or placebo injection. Reinforcing effects were also assessed after each injection with a Drug vs Money Multiple-Choice Form. Intravenous cocaine produced robust dose-related increases in subjective and reinforcing effects; these effects were not altered by nicotine maintenance. Intravenous caffeine produced elevations on several subjective ratings; nicotine maintenance did not affect these ratings. Under the placebo maintenance condition, intravenous nicotine produced robust dose-related subjective effects, with maximal increases similar to the high dose of cocaine; nicotine maintenance significantly decreased the subjective and reinforcing effects of intravenous nicotine. The results of the present study demonstrate that chronic nicotine maintenance produces tolerance to the effects of intravenous nicotine, but does not affect the subjective or reinforcing effects of cocaine or caffeine.

Acute nicotine reinforcement, but not chronic tolerance, predicts withdrawal and relapse after quitting smoking

Little research has examined the association of tobacco dependence with nicotine tolerance or reinforcement in a clinical sample. Smokers preparing to quit smoking participated in laboratory sessions to assess nicotine tolerance on subjective, cardiovascular, and performance measures and to assess nicotine reinforcement using a choice procedure. Participants were then provided with individual counseling (but no medication), made a quit attempt, and were followed for 1 year to determine clinical outcome, as determined by postquit withdrawal and days to relapse. Nicotine tolerance was unrelated to either withdrawal or relapse. However, acute nicotine reinforcement was significantly related to both greater withdrawal and faster relapse. Results challenge the common assumption that nicotine tolerance is closely related to dependence but suggest that nicotine reinforcement may have theoretical and clinical significance for dependence.

Cue dependency of nicotine self-administration and smoking

A paradox exists regarding the reinforcing properties of nicotine. The abuse liability associated with smoking equals or exceeds that of other addictive drugs, yet the euphoric, reinforcing and other psychological effects of nicotine, compared to these other drugs, are more subtle, are manifest under more restricted conditions, and do not readily predict the difficulty most smokers experience in achieving abstinence. One possible resolution to this apparent inconsistency is that environmental cues associated with drug delivery become conditioned reinforcers and take on powerful incentive properties that are critically important for sustaining smoking in humans and nicotine self-administration in animals. We tested this hypothesis by using a widely employed self-administration paradigm in which rats press a lever at high rates for 1 h/day to obtain intravenous infusions of nicotine that are paired with two types of visual stimuli: a chamber light that when turned on signals drug availability and a 1-s cue light that signals drug delivery. We show that these visual cues are at least as important as nicotine in sustaining a high rate of responding once self-administration has been established, in the degree to which withdrawing nicotine extinguishes the behavior, and in the reinstatement of lever pressing after extinction. Additional studies demonstrated that the importance of these cues was manifest under both fixed ratio and progressive ratio (PR) schedules of reinforcement. The possibility that nicotine-paired cues are as important as nicotine in smoking behavior should refocus our attention on the psychology and neurobiology of conditioned reinforcers in order to stimulate the development of more effective treatment programs for smoking cessation.