Reduced-Nicotine Cigarettes in Young Smokers: Impact of Nicotine Metabolism on Nicotine Dose Effects

Relationships Between the Nicotine Metabolite Ratio and Laboratory Assessments of Smoking Reinforcement and Craving Among Adults in a Smoking Cessation Trial

INTRODUCTION

People who metabolize nicotine more quickly are generally less successful at quitting smoking. However, the mechanisms that link individual differences in the nicotine metabolite ratio (NMR), a phenotypic biomarker of the rate of nicotine clearance, to smoking outcomes are unclear. We tested the hypotheses that higher NMR is associated with greater smoking reinforcement, general craving, and cue-induced cigarette craving in a treatment-seeking sample.

METHODS

Participants were 252 adults who smoke cigarettes enrolled in a randomized controlled smoking cessation trial (NCT03262662) conducted in Buffalo, New York, USA. Participants completed the Choice Behavior Under Cued Conditions (CBUCC) paradigm, a laboratory choice procedure, ~1 week before the first cessation treatment visit, at which time a saliva sample was collected for NMR assessment. On each CBUCC trial, participants reported cigarette craving during cue presentation (cigarette, water) and spent $0.01-$0.25 for a chance (5%-95%) to sample the cue (one puff, sip), providing measures of smoking reinforcement (spending for cigarettes vs. water), general cigarette craving (averaged across cigarette and water cues), and cue-specific craving (cigarette craving during cigarette vs. water cues).

RESULTS

As observed in prior work, the NMR was significantly higher among White and female participants. As expected, both spending and cigarette craving were significantly greater on cigarette compared to water trials. However, contrary to our hypotheses, higher NMR was not associated with greater smoking reinforcement, general craving, or cue-specific craving.

CONCLUSIONS

The present data do not support that smoking reinforcement or craving is related to nicotine metabolism among individuals seeking to quit smoking.

IMPLICATIONS

Though greater smoking reinforcement, general craving, and cue-specific craving are hypothesized to be linked to faster nicotine metabolism, there was no evidence of such relationships in the present sample of adults seeking to quit smoking. Further research, including replication and consideration of alternate hypotheses, is warranted to elucidate the mechanisms by which the NMR is related to smoking cessation.

Underreporting of non-study cigarette use by study participants confounds the interpretation of results from ambulatory clinical trial of reduced nicotine cigarettes

BACKGROUND

As part of its comprehensive plan to significantly reduce the harm from tobacco products, the US Food and Drug Administration is establishing a product standard to lower nicotine in conventional cigarettes to make them "minimally addictive or non-addictive". Many clinical studies have investigated the potential impact of such a standard on smoking behavior and exposure to cigarette constituents. These ambulatory studies required participants who smoke to switch to reduced nicotine study cigarettes. In contrast to clinical trials on pharmaceuticals or medical devices, participants had ready access to non-study conventional nicotine cigarettes and high rates of non-study cigarette use were consistently reported. The magnitude of non-compliance, which could impact the interpretation of the study results, was not adequately assessed in these trials.

METHODS

We conducted a secondary analysis of data from a large, randomized trial of reduced nicotine cigarettes with 840 participants to estimate the magnitude of non-compliance, i.e., the average number of non-study cigarettes smoked per day by study participants assigned to reduced nicotine cigarettes. Individual participants' non-study cigarette use was estimated based on his/her urinary total nicotine equivalent level, the nicotine content of the study cigarette assigned and the self-reported number of cigarettes smoked, using a previously published method.

RESULTS

Our analysis showed that (1) there is a large variation in the number of non-study cigarettes smoked by participants within each group (coefficient of variation 90-232%); (2) participants in reduced nicotine cigarette groups underreported their mean number of non-study cigarettes smoked per day by 85-91%; and (3) the biochemical-based estimates indicate no reduction in the mean number of total cigarettes smoked per day for any group assigned to reduced nicotine cigarettes after accounting for non-study cigarettes.

CONCLUSIONS

High levels of non-compliance, in both the rate and magnitude of non-study cigarette use, are common in ambulatory reduced nicotine cigarette trials where participants have access to conventional nicotine non-study cigarettes. The potential impact of high non-compliance on study outcomes should be considered when interpreting the results from such ambulatory studies.

The Impact of Reducing Nicotine Content on Adolescent Cigarette Smoking and Nicotine Exposure: Results From a Randomized Controlled Trial

INTRODUCTION

As the science base around the potential benefits of a reduced-nicotine standard for cigarettes grows, information on the potential effects on adolescent smokers is a high priority. The aim of this randomized trial was to test the influence of 3-week exposure to reduced nicotine cigarettes in a sample of adolescent daily smokers.

AIMS AND METHODS

In this double-blind, two-arm, randomized controlled trial (NCT0258731), following a 1-week baseline, adolescent daily smokers not currently intending to quit (ages 15-19 years, n = 66 randomized) were urn randomized to use either very low nicotine content (VLNC; 0.4 mg/g; n = 33) or normal nicotine content (NNC, 15.8 mg/g; n = 33) research cigarettes for 3 weeks. Participants attended five study sessions at our clinical laboratory. The primary outcome was average total cigarettes smoked per day (CPD; including both study and non-study cigarettes) at week 3.

RESULTS

Stepwise regression results demonstrated that compared with NNC cigarettes (n = 31), assignment to VLNC cigarettes (n = 29), was associated with 2.4 fewer CPD on average than NNC assignment (p < .05) week 3 when controlling for covariates (p < .01, Cohen's d = 0.52 n = 60 completed all procedures). VLNC cigarettes were also associated with lower levels of craving reduction than NNC cigarettes (Questionnaire on Smoking Urges Factor 2, p < .05). No group differences were found for secondary outcomes.

CONCLUSIONS

Adolescent participants assigned to VLNC use for 3 weeks smoked fewer total CPD relative to the NNC group. Overall, data suggest that a VLNC policy would reduce cigarette smoking in adolescents who smoke, but high rates of incomplete adherence suggest that youth may seek alternative sources of nicotine in this scenario.

IMPLICATIONS

The US Food and Drug Administration may enact a reduced-nicotine product standard that would affect all commercially available cigarettes. One important population affected by this policy would be adolescents who smoke. This study, the first clinical trial of VLNC cigarettes in adolescents, demonstrates that adolescents switched to VLNC cigarettes for 3 weeks reduced their CPD relative to the normal-nicotine cigarette control group, without leading to increased respiratory symptoms or increased withdrawal. Biomarkers indicated the use of other sources of nicotine, suggesting that such a policy will need to consider approaches to assist in transitioning away from smoking.

Smokers' Affective Responses to COVID-19-Related Health Warnings on Cigarette Packets: The Influence of Delay Discounting

INTRODUCTION

The addition of graphic health warnings to cigarette packets can facilitate smoking cessation, primarily through their ability to elicit a negative affective response. Smoking has been linked to COVID-19 mortality, thus making it likely to elicit a strong affective response in smokers. COVID-19-related health warnings (C19HW) may therefore enhance graphic health warnings compared to traditional health warnings (THW). Further, because impulsivity influences smoking behaviors, we also examined whether these affective responses were associated with delay discounting.

METHODS

In a between-subjects design, 240 smokers rated the valence and arousal elicited by tobacco packaging that contained either a C19HW or THW (both referring to death). Participants also completed questionnaires to quantify delay discounting, and attitudes towards COVID-19 and smoking (eg, health risks, motivation to quit).

RESULTS

There were no differences between the two health warning types on either valence or arousal, nor any secondary outcome variables. There was, however, a significant interaction between health warning type and delay discounting on arousal ratings. Specifically, in smokers who exhibit low delay discounting, C19HWs elicited significantly greater subjective arousal rating than did THWs, whereas there was no significant effect of health warning type on arousal in smokers who exhibited high delay discounting.

CONCLUSION

The results suggest that in smokers who exhibit low impulsivity (but not high impulsivity) C19HWs may be more arousing than THWs. Future work is required to explore the long-term utility of C19HWs, and to identify the specific mechanism by which delay discounting moderates the efficacy of tobacco health warnings.

IMPLICATIONS

The study is the first to explore the impact of COVID-19-related health warnings on cigarette packaging. The results suggest that COVID-19-related warnings elicit a similar level of negative emotional arousal, relative to traditional warnings. However, COVID-19 warnings, specifically, elicit especially strong emotional responses in less impulsive smokers, who report low delay discounting. Therefore, there is preliminary evidence supporting COVID-19 related warnings for tobacco products to aid smoking cessation. Additionally, there is novel evidence that, for some warnings, high impulsiveness may be a factor in reduced warning efficacy, which may explain poorer cessation success in this population.

Effects of very low nicotine content cigarettes on smoking across vulnerable populations

There has been long-standing interest in a reduced-nicotine product standard for combusted tobacco, which is within the regulatory purview of the Food and Drug Administration (FDA). In weighing whether to establish this standard, it is important to consider potential responses among people who are at elevated risk for tobacco-related health harms. In this narrative review, we summarize studies of very low nicotine content (VLNC) cigarettes conducted between 2010 and 2021 in groups that the FDA has identified as vulnerable populations. Studies conducted to date in adults with mental health conditions, adults with opioid use disorder, socioeconomically-disadvantaged adults, and youth or young adults indicate that immediate switching to VLNC cigarettes decreases smoking, with minimal or no unintended negative consequences. Few studies have investigated the effects of VLNC cigarettes in racial or ethnic minorities, people who smoke menthol cigarettes, and pregnant women, but initial findings suggest that responses of these individuals are similar to responses observed in other vulnerable populations. We are not aware of studies that have investigated VLNC cigarettes in military/veteran populations, sexual or gender minority individuals, or people living in underserved rural environments. Future research directions include understanding how to promote cessation in the context of a reduced-nicotine standard, and how to correct VLNC misperceptions in vulnerable populations. Nevertheless, the evidence to date indicates that a reduced-nicotine standard is likely to have the same beneficial effects on smoking reductions as it does in less vulnerable populations, which should provide some confidence in pursuing this regulatory approach.

Non-nicotine constituents in cigarette smoke extract enhance nicotine addiction through monoamine oxidase A inhibition

Tobacco addiction has been largely attributed to nicotine, a component in tobacco leaves and smoke. However, extensive evidence suggests that some non-nicotine components of smoke should not be overlooked when considering tobacco dependence. Yet, their individual effect and synergistic effect on nicotine reinforcement remain poorly understood. The study herein focused on the role of non-nicotine constituents in promoting the effects of nicotine and their independent reinforcing effects. Denicotinized cigarettes were prepared by chemical extracting of cut tobacco, and the cigarette smoke extracts (CSE, used as a proxy for non-nicotine ingredients) were obtained by machine-smoking the cigarettes and DMSO extraction. The compositions of harmful components, nicotine, and other minor alkaloids in both cut tobacco and the CSE of experimental denicotinized cigarettes were examined by GC-MS, and compared with 3R4F reference cigarettes. individually and in synergy with nicotine were determined by conditioned place preference (CPP), dopamine (DA) level detection, the open field test (OFT), and the elevated plus maze (EPM). Finally, the potential enhancement mechanism of non-nicotinic constituents was investigated by nicotine metabolism and monoamine oxidase A (MAOA) activity inhibition in the striatum of mice and human recombinant MAOA. Thenicotine content in smoke from the experimental denicotinized cigarettes (under ISO machine-smoking conditions) was reduced by 95.1% and retained most minor alkaloids, relative to the 3R4F reference cigarettes. It was found that non-nicotine constituents increased acute locomotor activities. This was especially pronounced for DA levels in NAc and CPP scores, decreased the time in center zone. There were no differences in these metrics with DNC group when compared to the NS group. Non-nicotine constituents alone did not show reinforcing effects in CPP or striatum DA levels in mice. However, in the presence of nicotine, non-nicotine constituents further increased the reinforcing effects. Furthermore, non-nicotine constituents may enhance nicotine's reinforcing effects by inhibiting striatum MAOA activity rather than affecting nicotine metabolism or total striatum DA content in mice. These findings expand our knowledge of the effect on smoking reinforcement of non-nicotine constituents found in tobacco products.

Cigarette smoking is associated with difficulties in the use of reappraisal for emotion regulation

BACKGROUND

Negative emotions can promote smoking relapse during a quit attempt. The use of cognitive reappraisal to self-regulate these emotions may therefore aid smoking cessation. Determining whether smokers exhibit difficulties in the use of reappraisal, and which factors are associated with such difficulties, may aid smoking cessations.

METHODS

50 smokers and 50 non-smokers completed an online reappraisal task in which they either reappraised or naturally experienced emotions induced by negatively- and neutrally-valenced images that presented situations in either the 1st-person or 3rd-person perspective. Participants also completed the Difficulties in Emotion Regulation Scale (DERS).

RESULTS

Compared to non-smokers, smokers were less successful in using reappraisal to self-regulate emotions elicited by negatively-valenced images (but not neutrally-valenced images). Importantly, this effect was only true for images that were presented in the 1st-person (but not 3rd-person) perspective. Contrary to predictions, there were no group differences in DERS scores.

CONCLUSIONS

This study provides the first evidence that smokers experience difficulties in the use of reappraisal, particularly in situations that appear to be happening to themselves. Because the use of this regulation technique may help smokers to quit, improving smokers' abilities to use reappraisal, particularly during negatively-valenced situations that directly influence the smoker, may aid smoking cessation.

A review of the evidence on cigarettes with reduced addictiveness potential

BACKGROUND

In May 2018, the Secretariat for the World Health Organization Framework Convention on Tobacco Control convened a meeting to discuss the potential for reducing the addictiveness of tobacco products. A central focus was to review research findings on the behavioral effects of reducing the addictiveness of cigarettes.

METHODS

This manuscript reports the results of a review of the behavioral science literature, updated through April 2021, with special attention to both the potential benefits and unintended consequences of reducing nicotine in cigarettes.

RESULTS

Available evidence suggests that reducing nicotine content in cigarettes to very low levels could benefit public health in three primary ways, by 1) decreasing uptake of regular smoking, 2) decreasing the amount people smoke, and 3) increasing the likelihood of smoking cessation. Current evidence also suggests that reducing nicotine in cigarettes may produce similar benefits across many important subpopulations of people who smoke, including those with psychiatric comorbidities, those who use other substances, those with low socioeconomic status, young people, people who smoke infrequently and people who prefer menthol cigarettes. Cigarette nicotine reduction could also lead to some undesirable outcomes, such as experiencing withdrawal, product manipulation, an illicit market, and harm misperceptions; strategies that may mitigate each are discussed.

CONCLUSION

Overall, behavioral research suggests product standards that limit the nicotine content of combusted tobacco products could render cigarettes and similar products less addictive. The availability of legal, non-combusted products that effectively substitute for cigarettes and the dissemination of public health campaigns that clarify misperceptions about the relationship between nicotine, tobacco and disease may facilitate the extent to which a nicotine reduction policy reduces smoking.

Daily and intermittent smoking are associated with low prefrontal volume and low concentrations of prefrontal glutamate, creatine, myo-inositol, and N-acetylaspartate

Cigarette smoking is still the largest contributor to disease and death worldwide. Successful cessation is hindered by decreases in prefrontal glutamate concentrations and gray matter volume due to daily smoking. Because nondaily, intermittent smoking also contributes greatly to disease and death, understanding whether infrequent tobacco use is associated with reductions in prefrontal glutamate concentrations and gray matter volume may aid public health. Eighty-five young participants (41 nonsmokers, 24 intermittent smokers, 20 daily smokers, mean age ~23 years old), underwent ¹ H-magnetic resonance spectroscopy of the medial prefrontal cortex, as well as structural magnetic resonance imaging (MRI) to determine whole-brain gray matter volume. Compared with nonsmokers, both daily and intermittent smokers exhibited lower concentrations of glutamate, creatine, N-acetylaspartate, and myo-inositol in the medial prefrontal cortex, and lower gray matter volume in the right inferior frontal gyrus; these measures of prefrontal metabolites and structure did not differ between daily and intermittent smokers. Finally, medial prefrontal metabolite concentrations and right inferior frontal gray matter volume were positively correlated, but these relationships were not influenced by smoking status. This study provides the first evidence that both daily and intermittent smoking are associated with low concentrations of glutamate, creatine, N-acetylaspartate, and myo-inositol and low gray matter volume in the prefrontal cortex. Future tobacco cessation efforts should not ignore potential deleterious effects of intermittent smoking by considering only daily smokers. Finally, because low glutamate concentrations hinder cessation, treatments that can normalize tonic levels of prefrontal glutamate, such as N-acetylcysteine, may help intermittent and daily smokers to quit.

Regulatory approaches and implementation of minimally addictive combusted products

INTRODUCTION

A joint meeting was held by the World Health Organization (WHO) and the Convention Secretariat of the WHO Framework Convention on Tobacco Control to examine the potential effects of a regulatory policy to reduce nicotine in cigarettes to minimally addictive levels. This paper reviews the feasibility of and approaches to implementing a nicotine product standard.

METHODS

Prior WHO reports on this topic were consulted and a systematic review of the scientific literature was conducted. The paper was reviewed by the participants at the aforementioned meeting and their feedback was incorporated.

RESULTS

The nicotine dose most likely to consistently reduce smoking behavior and dependence is < 0.4 mg nicotine/g tobacco. An immediate rather than a gradual nicotine reduction approach appears to be more beneficial. Smokers are likely to seek nicotine from alternate sources (e.g., nicotine replacement therapies, e-cigarettes) or potentially, the illegal market. As such, the availability of alternative products, as well as strong policies against illegal markets, can potentially mitigate unintended consequences. An effective reduced nicotine regulation must be imbedded in a comprehensive and strong tobacco control program that includes public education and surveillance. Barriers and challenges to implementing a nicotine product standard exist, particularly in low-capacity countries.

CONCLUSION

Not all countries will have the capacity to implement a regulation to reduce nicotine in cigarettes (and preferably other combusted tobacco products) to minimally addictive levels. However, for the countries that choose to implement it, such a policy could potentially dramatically reduce the burden of tobacco use.

Acute subjective sensory perceptions predict relative reinforcing effects of smoked nicotine

INTRODUCTION

Smoking is believed partially reinforcing via immediate sensory perceptions. Yet, unknown is whether a cigarette's relative reinforcing efficacy can be predicted by these perceptions and whether this relationship may vary due to constituents known to alter those perceptions.

METHODS

Sensory perceptions of acute smoking were examined as predictors of subsequent cigarette choice behavior. Also tested was whether nicotine content or menthol affected this relationship. Adult dependent smokers (N = 37) participated in five sessions comparing cigarettes varying in nicotine contents (NIC; 1.3, 2.3, 5.5, 11.2, and 17.4 mg/g), relative to the very lowest nicotine content, 0.4 mg/g (VLNC). Non-menthol (n = 17) and menthol (n = 20) cigarettes-matched on nicotine-were provided based on participant preference. One NIC was compared versus VLNC per session (single-blinded); NIC content order was randomized across sessions on separate days. Perceptions (e.g., "liking", "satisfying") were measured immediately after initial sampling of NIC or VLNC, followed by a validated puff-by-puff choice procedure to determine preference for each NIC versus VLNC.

RESULTS

NIC perceptions (difference from VLNC) and puff choices increased with nicotine. Menthol moderated associations between perceptions and nicotine; and between puff choices and nicotine. Perceptions were predictive of puff choice-greater magnitude of difference in perceptions between VLNC and NIC led to more NIC puff choices. When testing perceptions' prediction of puff choices, neither the main effect of menthol or interaction of Perceptions X Nicotine Condition were significant.

CONCLUSIONS

Consistent with assumed-but rarely tested-causes of smoking reinforcement, sensory perceptions from a cigarette predict its relative reinforcing efficacy.

Acute effects of a very low nicotine content cigarette on laboratory smoking lapse: Impacts of nicotine metabolism and nicotine dependence

Reducing cigarette nicotine content to nonaddictive levels facilitates smoking cessation; however, very low nicotine content cigarettes (VLNCs) may not be equally effective across heterogeneous smokers. We evaluated the impact of acute VLNC smoking versus control (sham puffs) on craving, withdrawal and smoking lapse behaviour and whether genetically influenced differences in nicotine metabolism and individual differences in nicotine dependence moderate observed effects. Thirty-three overnight-abstinent smokers (15 slow vs. 17 normal nicotine metabolizers; 17 low vs. 16 high nicotine dependence) smoked a 0.05-mg nicotine VLNC during one session and took sham VLNC puffs during another session, in a counterbalanced order. Craving and withdrawal were assessed before and after smoking and sham puffing. Next, participants completed the McKee Smoking Lapse Task, which measures ability to resist smoking and quantity of ad libitum smoking. VLNC (vs. sham) reduced craving and withdrawal, increased ability to resist smoking and reduced ad libitum smoking. VLNC-induced reduction in craving for positive reinforcement was greater in slow (vs. normal) metabolizers. Nicotine metabolism did not moderate any other VLNC responses. High-dependence (vs. low-dependence) participants engaged in greater ad lib smoking across VLNC and sham conditions. Nicotine dependence did not moderate VLNC responses. VLNC reduced craving, withdrawal and smoking lapse behaviour. Individual differences in nicotine metabolism and dependence had a minimal impact on VLNC responses; however, VLNCs were less effective at reducing craving for positive reinforcement among normal (vs. slow) metabolizers. These findings suggest that desirable VLNC effects may extend across heterogeneous groups of smokers.

Neural Basis of Smoking-Related Difficulties in Emotion Regulation

BACKGROUND

Negative emotional states contribute to cigarette smoking, and difficulties in regulating these states can hinder smoking cessation. Understanding the neural bases of these difficulties in smokers may facilitate development of novel therapies for Tobacco Use Disorder.

METHODS

Thirty-seven participants (18 smokers, 19 nonsmokers; 16-21 years old) completed the Difficulties in Emotion Regulation Scale (DERS), which is comprised of 6 subscales (lack of emotional clarity, lack of emotional awareness, limited access to emotion regulation strategies, nonacceptance of emotional responses, difficulties engaging in goal-directed behaviors, and impulse control difficulties) that combine to provide a total score. Participants also underwent functional magnetic resonance imaging to determine resting-state functional connectivity of the amygdala. Separate ANOVAs were used to determine group differences in self-reports on the DERS. Voxel-wise linear mixed models were performed to determine whether group influenced relationships between whole-brain functional connectivity of the amygdala and scores on the DERS.

RESULTS

Compared with nonsmokers, smokers reported greater difficulties in emotion regulation, denoted by higher total scores on the DERS. Group differences were observed on a subscale of lack of emotional clarity, but no other subscale differences on the DERS were observed. Nonsmokers exhibited a greater negative correlation than smokers between lack of emotional clarity scores and connectivity of the amygdala with the left inferior frontal gyrus. Finally, this amygdala-to-left inferior frontal gyrus connectivity was weaker in smokers than in nonsmokers.

CONCLUSIONS

These findings suggest that difficulties in emotion regulation in smokers are at least partially due to lack of emotional clarity. Given the role of the inferior frontal gyrus in understanding emotional states, strengthening connectivity between the amygdala and the inferior frontal gyrus may improve emotional clarity to help smokers regulate their negative emotions, thereby improving their ability to quit smoking.

Differences in acute reinforcement across reduced nicotine content cigarettes

RATIONALE

The smallest difference in nicotine that can change a smoker's cigarette preference is not clearly known.

OBJECTIVE

A procedure to efficiently identify the difference in nicotine needed to change cigarette preference could help inform research to gauge effects of a nicotine reduction policy.

METHODS

Using a within-subject design, we assessed preference for research cigarettes varying in nicotine contents (NIC; 18.7, 10.8, 5.3, 2.3, and 1.3 mg/g of tobacco), relative to a very low nicotine cigarette (VLNC; 0.4 mg/g), in 17 adult-dependent non-menthol smokers abstinent overnight. Only one NIC was compared vs. the VLNC per session, with order of the five NIC contents randomized across sessions on five separate days. Preference for each NIC vs. VLNC was determined by validated forced choice procedure, with those NIC chosen more than VLNC indicating greater reinforcement due to greater nicotine per se. Secondarily, less preference for lower NIC (vs. VLNC), relative to choice for the highest NIC, 18.7 mg/g (vs. VLNC), indexed reduced reinforcement.

RESULTS

Overall, NIC choices increased as their nicotine increased, as anticipated. Relative to the 0.4 mg/g VLNC, choice was greater for NIC ≥ 5.3 mg/g but not ≤ 2.3 mg/g. Correspondingly, relative to choice for 18.7 mg/g, choice was less for NIC ≤ 2.3 mg/g but not ≥ 5.3 mg/g.

CONCLUSIONS

Although replication with larger samples and longer access is needed, results indicate that nicotine reduction to ≤ 2.3 mg/g in cigarettes would attenuate reinforcement. This choice procedure may efficiently inform future clinical trials to assess relative reinforcing effects of smoking reduced nicotine cigarettes.

Nicotine Reduction in Cigarettes: Literature Review and Gap Analysis

BACKGROUND

The US Food and Drug Administration (FDA) is considering reducing nicotine levels in cigarettes to "minimally or non-addictive levels." However, important research gaps remain, and the FDA must determine when the available research is sufficient to support moving forward.

METHODS

The authors conducted a systematic review of research articles in PubMed relating to nicotine reduction. Building on a review of risk assessment best practices, the authors also developed a risk assessment framework for tobacco regulation and used it to guide a gap analysis of nicotine reduction research.

RESULTS

The final sample consisted of 78 articles. The majority examined either nicotine dependence on very low nicotine cigarettes (VLNCs) or markers of potential health effects of using VLNCs. One-third of the identified articles reported results from four large randomized controlled trials (RCTs). While these studies report promising results and suggest that a nicotine reduction rule would be a powerful tool to reduce cigarette smoking, our gap analysis suggests that there is a need for studies that better reflect the use and availability of a wide range of tobacco/nicotine products and the potential for dual- or multi-product use.

CONCLUSION

The current body of research on nicotine reduction is weighted towards RCTs, which is appropriate for a policy that has not yet been implemented anywhere in the world. The FDA must consider a wide range of factors that may impact a product standard's public health impact, including those difficult to assess in RCTs, such as a nicotine reduction rule's impact on smoking initiation and relapse.

IMPLICATIONS

This systematic review presents a gap analysis based on a risk assessment framework to help identify remaining research priorities to inform FDA's potential product standard to reduce nicotine levels in cigarettes. Quickly addressing those gaps would support the FDA's effort to develop a nicotine reduction product standard that will be effective and withstand legal challenges.

Age Moderates Smokers' Subjective Response to Very-Low Nicotine Content Cigarettes: Evidence from a Randomized Controlled Trial

INTRODUCTION

Reducing the level of nicotine in cigarettes is a regulatory strategy that has the potential to greatly improve public health. If nicotine levels are reduced in all commercially available cigarettes, current smokers might find it easier to quit and young people might be less likely to become dependent. However, it is not yet known whether age moderates subjective or behavioral responses to low-nicotine cigarettes.

METHODS

Recently, a large, multisite randomized clinical trial was conducted to compare the effects of cigarettes differing in nicotine content (either usual-brand or research cigarettes containing 15.8, 5.2, 2.4, 1.3, or 0.4 mg nicotine/g tobacco) across 6 weeks of exposure. In this secondary analysis, we tested whether age moderated smokers' subjective (measures of psychological reward, smoking satisfaction) and behavioral (cigarettes smoked per day, smoking topography, and nicotine exposure) responses to cigarettes varying in nicotine content after 2 and 6 weeks of use, while controlling for baseline dependence and demographic factors.

RESULTS

Results indicated that younger adults (age 18-24) who smoked cigarettes with 2.4-0.4 mg/g nicotine reported significantly less smoking satisfaction and psychological reward, and smoked fewer cigarettes per day, than older adults (25+ years) after 2 weeks of use. No differences in topography were observed at either time point. After 6 weeks of use, differences had diminished on all measures.

CONCLUSIONS

The reduced positive effects of reduced-nicotine content cigarettes in young adults suggests that this regulatory policy may reduce smoking reinforcement in this vulnerable population.

IMPLICATIONS

As the FDA considers reducing the level of nicotine in cigarettes to make them less addictive, understanding the potential impact of this policy on young people is of crucial importance. We found that young adults had significantly lower positive subjective effects to very-low nicotine content (VLNC) cigarettes and smoked fewer VLNC cigarettes than older adults after 2 weeks of use, indicating that this policy may reduce smoking reinforcement more quickly in young adults. These data add to the growing body of evidence on the potential for this policy to positively affect public health.

Nicotine Effects, Body Weight Concerns and Smoking: A Literature Review

How people become addicted to cigarette smoking and remain addicted despite repeated attempts to quit requires piecing together a rather complex puzzle. The present review contextualizes the role of nicotine and smoking sensory stimulation on maintaining smoking, describes nicotine's effects on feeding behavior and body weight, and explores the impact of smoking outcome expectancies, including the belief that nicotine suppresses appetite and body weight, on the decision to smoke or vape (use of e-cigarettes). The analysis concludes with a review of rat models of human nicotine intake that attempt to isolate the effects of nicotine on appetite and weight gain. Animal research replicates with relative closeness phenomena observed in smokers, but the rat model falls short of replicating the long-term weight gain observed post-smoking cessation.

The Impact of Gradual and Immediate Nicotine Reduction on Subjective Cigarette Ratings

BACKGROUND

A recent clinical trial showed that an immediate transition to very low nicotine content (VLNC) cigarettes, compared with a gradual transition, produced greater reductions in smoking behavior, smoke exposure, and dependence. However, there was less compliance with the instruction to smoke only VLNC cigarettes in the immediate versus gradual reduction condition. The goal of this study was to test whether nicotine reduction method alters subjective ratings of VLNC cigarettes, and whether subjective ratings mediate effects of nicotine reduction method on smoking behavior, smoke exposure, dependence, and compliance.

METHODS

This is a secondary analysis of a randomized trial conducted across 10 sites in the United States. Smokers (n = 1250) were randomized to either a control condition, or to have the nicotine content of their cigarettes reduced immediately or gradually to 0.04 mg nicotine/g of tobacco during a 20-week study period. Participants completed the modified Cigarette Evaluation Questionnaire (mCEQ).

RESULTS

After Week 20, the immediate reduction group scored significantly lower than the gradual reduction group on multiple subscales of the mCEQ (ps < .001). The Satisfaction subscale of the mCEQ mediated the impact of nicotine reduction method on smoke exposure, smoking behavior, dependence, compliance, and abstinence. Other subscales also mediated a subset of these outcomes.

CONCLUSIONS

An immediate reduction in nicotine content resulted in lower product satisfaction than a gradual reduction, suggesting that immediate reduction further reduces cigarette reward value. This study will provide the Food and Drug Administration with information about the impact of nicotine reduction method on cigarette reward value.

IMPLICATIONS

These data suggest that an immediate reduction in nicotine content will result in greater reductions in cigarette satisfaction than a gradual reduction, and this reduction in satisfaction is related to changes in smoking behavior and dependence.

Neural basis of smoking-induced relief of craving and negative affect: Contribution of nicotine

Smoking-induced relief of craving and withdrawal promotes continued cigarette use. Understanding how relief is produced and the role of nicotine in this process may facilitate development of new smoking-cessation therapies. As the US Food and Drug Administration considers setting a standard for reduced nicotine content in cigarettes to improve public health, knowledge of how nicotine contributes to relief also can inform policy. We assessed effects of nicotine using resting state functional magnetic resonance imaging (MRI) and behavioral assessments of craving and negative affect. Twenty-one young (18-25 years old) daily smokers underwent overnight abstinence on 4 days. On each of the following mornings, they self-rated their cigarette craving and negative affect and underwent resting-state functional MRI (fMRI) before and after smoking a cigarette that delivered 0.027, 0.110, 0.231, or 0.763 mg of nicotine. Functional connectivity between the anterior insula and anterior cingulate cortex (ACC) and between the nucleus accumbens and orbitofrontal cortex (OFC) was assessed. Smoking reduced craving, negative affect, and nucleus accumbens-OFC connectivity irrespective of nicotine dose, with positive correlations of the effects on behavioral and connectivity measures. Only the highest nicotine dose (0.763 mg) reduced right anterior insula-ACC connectivity; this reduction was positively correlated with the behavioral effects of the 0.763-mg dose only. While nicotine-based therapies may act on right anterior insula-ACC functional circuits to facilitate smoking cessation, non-nicotine (eg, the conditioned and sensorimotor) aspects of smoking may promote cessation by reducing OFC-accumbens connectivity to alleviate withdrawal.

A Pilot Study of E-Cigarette Naïve Cigarette Smokers and the Effects on Craving After Acute Exposure to E-Cigarettes in the Laboratory

BACKGROUND AND OBJECTIVES

Recent surveys confirm continued increases in the use of electronic-cigarettes (e-cigarettes) in adolescents and adults. Users often state that e-cigarettes reduce tobacco craving and withdrawal symptoms in addition to their smoking. Data from laboratory studies and clinical trials have confirmed these statements, though there are inconsistencies in the outcomes. In this pilot study, we set out to evaluate the effects of e-cigarettes, as compared to the participants' own cigarettes, on baseline craving and smoking severity.

METHODS

Using a within-subjects, placebo-controlled study design, 15 tobacco-dependent, e-cigarette naïve participants sustained abstinence overnight. They completed distinct phases of this protocol during four separate study sessions. Participants were randomized to an e-cigarette device containing one of three doses of nicotine (0, 18, or 36 mg/ml) or their own cigarette. Each study visit was ~3 hours long and separated by at least 7 days. Visits included assessments of craving and smoking severity.

RESULTS

The data showed that after 10 puffs in both the Own cigarette and e-cigarette conditions, breath carbon monoxide levels increased significantly in the former but not the latter. Questionnaire of Smoking Urges and Choices to Smoke scores were not statistically different across groups after two distinct bouts of 10 puffs each. Additionally, E-cigarette Perceptions Questionnaire responses were not significantly different according to dose.

CONCLUSION AND SCIENTIFIC SIGNIFICANCE

This experiment provides data demonstrating that e-cigarettes did not reduce craving or smoking severity in e-cigarette naïve users. However, since this was a pilot study, the conclusions that can be drawn are limited. (Am J Addict 2019;28:361-366).

Not all smokers appear to seek nicotine for the same reasons: implications for preclinical research in nicotine dependence

Tobacco use leads to 6 million deaths every year due to severe long-lasting diseases. The main component of tobacco, nicotine, is recognized as one of the most addictive drugs, making smoking cessation difficult, even when 70 percent of smokers wish to do so. Clinical and preclinical studies have demonstrated consistently that nicotine seeking is a complex behavior involving various psychopharmacological mechanisms. Evidence supports that the population of smokers is heterogeneous, particularly as regards the breadth of motives that determine the urge to smoke. Here, we review converging psychological, genetic and neurobiological data from clinical and preclinical studies supporting that the mechanisms controlling nicotine seeking may vary from individual to individual. It appears timely that basic neuroscience integrates this heterogeneity to refine our understanding of the neurobiology of nicotine seeking, as tremendous progress has been made in modeling the various psychopharmacological mechanisms driving nicotine seeking in rodents. For a better understanding of the mechanisms that drive nicotine seeking, we emphasize the need for individual-based research strategies in which nicotine seeking, and eventually treatment efficacy, are determined while taking into account individual variations in the mechanisms of nicotine seeking.

Response to reduced nicotine content cigarettes among smokers differing in tobacco dependence severity

This study examines whether tobacco dependence severity moderates the acute effects of reducing nicotine content in cigarettes on the addiction potential of smoking, craving/withdrawal, or smoking topography. Participants (N = 169) were daily smokers with mild, moderate, or high tobacco-dependence severity using the Heaviness of Smoking Index. Following brief abstinence, participants smoked research cigarettes varying in nicotine content (0.4, 2.4, 5.2, 15.8 mg nicotine/g tobacco) in a within-subject design. Results were analyzed using repeated measures analysis of co-variance. No main effects of dependence severity or interactions with nicotine dose were noted in relative reinforcing effects in concurrent choice testing or subjective effects on the modified Cigarette Evaluation Questionnaire. Demand for smoking in the Cigarette Purchase Task was greater among more dependent smokers, but reducing nicotine content decreased demand independent of dependence severity. Dependence severity did not significantly alter response to reduced nicotine content cigarettes on the Minnesota Tobacco Withdrawal Scale nor Questionnaire of Smoking Urges-brief (QSU) Factor-2 scale; dependence severity and dose interacted significantly on the QSU-brief Factor-1 scale, with reductions dependent on dose among highly but not mildly or moderately dependent smokers. Dependence severity and dose interacted significantly on only one of six measures of smoking topography (i.e., maximum flow rate), which increased as dose increased among mildly and moderately but not highly dependent smokers. These results suggest that dependence severity has no moderating influence on the ability of reduced nicotine content cigarettes to lower the addiction potential of smoking, and minimal effects on relief from craving/withdrawal or smoking topography.

Reduced Nicotine Content Cigarettes and Cannabis Use in Vulnerable Populations

Objective: We estimated whether recent cannabis use moderates response to cigarettes varying in nicotine content (0.4, 2.4, 5.2, 15.8 mg/g) among smokers with concurrent affective disorders, opioid dependence, or socioeconomic disadvantage. Methods: We conducted a secondary analysis of a multi-site, double-blind, laboratory study examining acute response to reduced nicotine content cigarettes (RNCC) in 169 adult smokers with co-morbid conditions. Participants positive for recent cannabis use or self-reported past 30-day cannabis use at baseline were categorized as current cannabis users (N = 63). Repeated measures analysis of variance tests assessed whether baseline cannabis use moderated cigarette reinforcement, tobacco withdrawal, craving, smoking topography, or carbon monoxide boost. Results: Cannabis users were younger, less educated, and had more depression and anxiety than non-users (p < .05). Cannabis use status did not moderate the effects of nicotine dose on concurrent choice testing, subjective effects of RNCCs, or smoking topography. After adjusting for sociodemographic characteristics, cannabis users had higher ratings on Smoking Satisfaction, Enjoyment of Respiratory Tract Sensations, and Craving Reduction across all nicotine doses. Cannabis users reported longer withdrawal symptom duration and more rapid decline of carbon monoxide boost than non-users. Conclusions: Findings suggest RNCCs decrease the addiction potential of cigarettes in vulnerable populations independent of cannabis use status.

Association of Reduced Nicotine Content Cigarettes With Smoking Behaviors and Biomarkers of Exposure Among Slow and Fast Nicotine Metabolizers: A Nonrandomized Clinical Trial

IMPORTANCE

The US Food and Drug Administration (FDA) has announced its intention to reduce the nicotine content in combustible cigarettes but must base regulation on public health benefits. Fast nicotine metabolizers may be at risk for increased smoking following a national nicotine reduction policy. We hypothesized that using reduced nicotine content (RNC) cigarettes would be associated with increases in smoking behaviors and exposure among smokers with a fast-but not slow-nicotine-metabolite ratio (NMR).

OBJECTIVES

To examine the association of RNC cigarettes with smoking behaviors and biomarkers of exposure and to compare these associations in fast and slow metabolizers of nicotine based on the NMR.

DESIGN SETTING AND PARTICIPANTS

A 35-day, 3-period, within-participant nonrandomized clinical trial was conducted at an academic medical center in Philadelphia, Pennsylvania. A 5-day baseline period using the smokers' preferred brand of cigarettes was followed by 2 consecutive 15-day periods using free investigational RNC cigarettes. A total of 100 daily, non-treatment-seeking, nonmenthol cigarette smokers (59 fast, 41 slow metabolizers) were recruited from December 24, 2013, to December 2, 2015. Data analysis was performed from December 12, 2016, to January 3, 2018.

INTERVENTIONS

Two 15-day periods using cigarettes containing 5.2 mg (RNC1) and 1.3 mg (RNC2) of nicotine per gram of tobacco.

MAIN OUTCOMES AND MEASURES

Smoking behaviors (number of cigarettes per day [CPD], total puff volume) and biomarkers of exposure (carbon monoxide [CO], urine total nicotine equivalents [TNE], and 4-[methylnitrosamino]-1-[3-pyridyl]-1-butanol [NNAL]).

RESULTS

Smokers (73 [73.0%] men; 74 [74.0%] white; mean [SD] age, 43.02 [12.13] years; mean [SD] CPD, 17.31 [5.72]) consumed 2.62 (95% CI, 1.54-3.70) more CPD during the RNC1 period vs their preferred brand during baseline (P < .001) and approximated baseline CPD during the RNC2 period (mean difference, 0.96 [95% CI, -0.36 to 2.28]; P = .24). Additional outcome measures were lower during both RNC periods vs baseline (total puff volume, mean [95% CI]: RNC1, 537 mL [95% CI, 479-595 mL]; RNC2, 598 mL [95% CI, 547-649 mL] vs baseline, 744 mL [95% CI, 681-806 mL]; TNE, mean [95% CI]: RNC1, 30.9 nmoL/mg creatinine [95% CI, 26.0-36.6 nmoL/mg]; RNC2, 22.8 nmoL/mg creatinine [95% CI, 17.8-29.0 nmoL/mg] vs baseline, 54.6 nmoL/mg creatinine [95% CI, 48.1-62.1 nmoL/mg]; and NNAL, mean [95% CI]: RNC1, 229 pg/mg creatinine [95% CI, 189-277 pg/mg]; RNC2, 190 pg/mg creatinine [95% CI, 157-231 pg/mg] vs baseline, 280 pg/mg creatinine [95% CI, 231-339 pg/mg]; all P < .001). Carbon monoxide measures were similar across study periods (CO boost [SD], RNC1, 4.6 ppm [4.1-5.1 ppm]; RNC2, 4.2 ppm [3.7-4.6 ppm]; and baseline, 4.4 ppm [3.8-4.9 ppm]). The RNC cigarette associations did not differ by NMR.

CONCLUSIONS AND RELEVANCE

Both RNC cigarettes were associated with decreased puffing and urinary biomarker exposure but not with decreased daily cigarette consumption or CO levels. The NMR did not moderate associations at the nicotine levels tested, suggesting that fast metabolizers may not be at greater risk of increasing use or exposure from these products should the FDA mandate an RNC standard for cigarettes.

Adolescent smokers' response to reducing the nicotine content of cigarettes: Acute effects on withdrawal symptoms and subjective evaluations

BACKGROUND

Mandating a reduction in the nicotine content of cigarettes to a minimally addictive level could dramatically reduce smoking rates in the US. However, little is known about the effects of reduced nicotine content cigarettes in adolescents.

METHODS

Following overnight abstinence, adolescent daily smokers (ages 15-19, n = 50) reported on their craving, withdrawal, and positive and negative affect pre- and post- ad lib smoking of one cigarette containing varying nicotine content (15.8, 5.2, 1.3 and 0.4 mg/g of tobacco) in the laboratory and reported their subjective evaluations of each cigarette. Carbon monoxide (CO) boost from pre- to post-cigarette was calculated to determine if lower-nicotine cigarettes led to differential acute changes in toxicant exposure.

RESULTS

All four nicotine cigarette types significantly reduced abstinence-induced craving, withdrawal, and negative affect (all p's < .05). Mixed models evaluating the effect of nicotine content, with nicotine dependence level and gender included as covariates, revealed a significant effect of nicotine content on craving and subjective evaluations: higher nicotine content resulted in greater reductions in craving and increases in both positive and negative subjective evaluations. There were no significant effects of nicotine dose on withdrawal symptoms, negative affect, or CO boost.

CONCLUSIONS

These results suggest that lower nicotine cigarettes might result in reduced abuse liability compared to higher nicotine content cigarettes due to reduced positive subjective effects, while still reducing withdrawal, in adolescents. These results highlight the potential feasibility of this policy approach and support continued research on how a nicotine reduction policy may affect adolescent smoking patterns.

Functional Connectivity of the Raphe Nuclei: Link to Tobacco Withdrawal in Smokers

BACKGROUND

Although nicotine alters serotonergic neurochemistry, clinical trials of serotonergic medications for smoking cessation have provided mixed results. Understanding the role of serotonergic dysfunction in tobacco use disorder may advance development of novel pharmacotherapies.

METHODS

Functional magnetic resonance imaging was used to measure resting-state functional connectivity of the raphe nuclei as an indicator of serotonergic function. Connectivity of the dorsal and median raphe nuclei was compared between 18 young smokers (briefly abstinent, ~40 minutes post-smoking) and 19 young nonsmokers (16-21 years old); connectivity was also examined in a separate sample of overnight-abstinent smokers (18-25 years old), before and after smoking the first cigarette of the day. Relationships between connectivity of the raphe nuclei with psychological withdrawal and craving were tested in smokers.

RESULTS

Connectivity of the median raphe nucleus with the right hippocampal complex was weaker in smokers than in nonsmokers and was negatively correlated with psychological withdrawal in smokers. In overnight-abstinent smokers, smoking increased connectivity of the median raphe nucleus with the right hippocampal complex, and the increase was positively correlated with the decrease in psychological withdrawal.

CONCLUSIONS

Relief of withdrawal due to smoking is potentially linked to the serotonergic pathway that includes the median raphe nucleus and hippocampal complex. These results suggest that serotonergic medications may be especially beneficial for smokers who endorse strong psychological withdrawal during abstinence from smoking.

Effects of reduced nicotine content cigarettes on individual withdrawal symptoms over time and during abstinence

In the United States, the Food and Drug Administration (FDA) has initiated a public dialogue about reducing the nicotine content of cigarettes. A reduced-nicotine standard could increase withdrawal symptoms among current smokers. We examined the impact of switching smokers to cigarettes that varied in nicotine content on withdrawal symptoms over 6 weeks. A secondary analysis (N = 839) of a 10-site, double-blind clinical trial of nontreatment-seeking smokers was completed. Participants were instructed to smoke study cigarettes, containing 0.4 to 15.8 mg of nicotine/g of tobacco, for 6 weeks and were then abstinent overnight. Using latent growth curves, trajectories of individual withdrawal symptoms were compared between the reduced nicotine content (RNC) conditions and a normal nicotine content (NNC) condition. Path analyses compared symptoms after overnight abstinence. Relative to NNC cigarettes, participants smoking RNC cigarettes had increased anger/irritability/frustration and increased appetite/weight gain during the initial weeks, but the symptoms resolved by Week 6. Individuals who were biochemically verified as adherent with using only the 0.4 mg/g cigarettes had higher sadness levels (Cohen's d = .40) at Week 6 compared with the NNC condition, although symptoms were mild. After a post-Week 6 overnight abstinence challenge, some RNC conditions relative to NNC condition exhibited reduced withdrawal. Individuals who were biochemically confirmed as adherent to the lowest nicotine condition experienced only mild and transient symptom elevations. Thus, a reduced-nicotine standard for cigarettes produced a relatively mild and temporary increase in withdrawal among nontreatment-seeking smokers (ClinicalTrials.gov No. NCT01681875). (PsycINFO Database Record

Cox C, London ED. Behavioral and neural markers of cigarette-craving regulation in young-adult smokers during abstinence and after smoking

Cigarette craving contributes substantially to the maintenance of tobacco use disorder. Behavioral strategies to regulate craving may facilitate smoking cessation but remain underexplored. We adapted an emotion-regulation strategy, using proximal/distal self-positioning, to the context of cigarette craving to examine craving regulation in 42, daily smokers (18-25 years old). After overnight abstinence from smoking, before and after smoking their first cigarette of the day, participants viewed videos of natural scenes presenting young adults who were either smoking cigarettes ("smoke") or not ("non-smoke"). Before each video, participants were instructed to imagine themselves either immersed in the scene ("close") or distanced from it ("far"). They rated their craving after each video. Task-based fMRI data are presented for a subsample of participants (N = 21). We found main effects of smoking, instruction, and video type on craving-lower ratings after smoking than before, following the "far" vs. "close" instructions, and when viewing non-smoke vs. smoke videos. Before smoking, "smoke" vs. "non-smoke" videos elicited activation in, orbitofrontal cortex, anterior cingulate, lateral parietal cortex, mid-occipital cortex, ventral striatum, dorsal caudate, and midbrain. Smoking reduced activation in anterior cingulate, left inferior frontal gyrus, and bilateral temporal poles. Activation was reduced in the ventral striatum and medial prefrontal cortex after the "far" vs. the "close" instruction, suggesting less engagement with the stimuli during distancing. The results indicate that proximal/distal regulation strategies impact cue-elicited craving, potentially via downregulation of the ventral striatum and medial prefrontal cortex, and that smoking during abstinence may increase cognitive control capacity during craving regulation.

Influence of Nicotine Metabolism Ratio on [11C]-(+)-PHNO PET Binding in Tobacco Smokers

BACKGROUND

Identifying the biological basis of smoking cessation success is of growing interest. The rate of nicotine metabolism, measured by the nicotine metabolite ratio, affects multiple aspects of nicotine dependence. Fast nicotine metabolizers tend to smoke more, experience more withdrawal and craving, and have lower cessation rates compared with slow metabolizers. The nicotine metabolite ratio predicts treatment response, and differences in brain activation between fast metabolizers and slow metabolizers have been reported in fMRI studies. As reinforcing/rewarding effects of tobacco are associated with dopamine transmission, the purpose of the present study was to study the dopaminergic system in human smokers based on their nicotine metabolite ratio.

METHODS

The first aim of the study was to explore if there were differences in D2 and D3 receptor binding between fast metabolizers and slow metabolizers during abstinence. The second aim was to explore smoking-induced dopamine release in both groups. Participants underwent 2 [11C]-(+)-PHNO PET scans: one scan during abstinence and the other after smoking a tobacco cigarette. Subjective measures were recorded and blood was drawn for measurement of nicotine and cotinine levels.

RESULTS

During abstinence, slow metabolizers (n = 13) had lower [11C]-(+)-PHNO binding potential than fast metabolizers (n = 15) restricted to the D2 regions of the associative striatum and sensorimotor striatum. After smoking a cigarette, [11C]-(+)-PHNO binding potential was decreased in the limbic striatum and ventral pallidum, suggestive of increases in dopamine, but there were no nicotine metabolite ratio differences.

CONCLUSIONS

Further studies are required to delineate if differences in [11C]-(+)-PHNO binding between slow metabolizers and fast metabolizers at abstinence baseline are preexisting traits or induced by prolonged tobacco use.

Sex differences in tobacco withdrawal and responses to smoking reduced-nicotine cigarettes in young smokers

RATIONALE

Policies that establish a standard for reduced nicotine content in cigarettes can decrease the prevalence of smoking in the USA. Cigarettes with nicotine yields as low as 0.05 mg produce substantial occupancy of nicotinic acetylcholine receptors (26%), but women and men respond differently to these cigarettes.

OBJECTIVE

This study aimed to measure responses to smoking cigarettes that varied widely in nicotine yields, investigating whether sex differences in the effects on craving, withdrawal, and affect would be observed at even lower nicotine yields than previously studied, and in young smokers.

METHODS

Overnight abstinent young smokers (23 men, 23 women, mean age 22.18) provided self-reports of craving, withdrawal, and affect before and after smoking cigarettes with yields of 0.027, 0.110, 0.231, or 0.763 mg nicotine, and evaluated characteristics of each cigarette.

RESULTS

Compared to abstinent young men, abstinent young women reported greater negative affect, psychological withdrawal, and sedation, all of which were relieved equally by all cigarettes. Men but not women reported greater craving reduction, perceived nicotine content, and cigarette liking with increasing nicotine dose.

CONCLUSIONS

Men may experience less smoking-related relief of craving, and enjoy cigarettes less, if nicotine yields are reduced to very low levels. Conversely, women respond equally well to cigarettes with nicotine yields as low as 0.027 mg as to cigarettes with nicotine yields 28-fold higher (0.763 mg). These differences are relevant for policy regarding reduced nicotine in cigarettes and may influence the efficacy and acceptability of reduced-nicotine cigarettes as smoking cessation aids.