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

The Relative Reinforcing Value of Menthol Among Young Adult Cigarette Smokers: Results From a Behavioral Choice Task

INTRODUCTION

Menthol cigarettes are associated with experimentation and progression to regular use. Although reinforcement processes likely underlie menthol's appeal, the reinforcing value of menthol cigarettes remains unknown.

AIMS AND METHODS

This study examined the relative reinforcing value (RRV) of menthol versus nonmenthol cigarettes in young adult menthol (n = 54) and nonmenthol (n = 53) smokers, and differences in menthol's RRV by race, ethnicity, and sexual orientation. Overnight abstinent participants completed a choice task assessing willingness to "work" to click targets on a computer screen to earn menthol or nonmenthol cigarette puffs. A progressive ratio schedule was used where the menthol target had to be clicked progressively more times, over 10 trials, to earn a menthol cigarette puff, while clicks for the nonmenthol target were fixed across trials. RRV for menthol was defined by the breakpoint, or the highest trial (out of to 10) completed for a menthol cigarette puff. Number of clicks for menthol and nonmenthol puffs were also examined.

RESULTS

Menthol smokers worked harder for menthol versus nonmenthol cigarette puffs (breakpoint = 9.17; ~1236 clicks vs. 24 clicks). Breakpoint was higher among Hispanic (6.49) versus NH White (4.83) and NH non-White smokers (4.43). In exploratory analyses of interactions of menthol preference with race and ethnicity, nonmenthol Hispanic smokers worked harder for menthol cigarette puffs versus NH non-White and NH White nonmenthol smokers.

CONCLUSIONS

Menthol cigarettes are highly reinforcing for young adult menthol and Hispanic smokers. A menthol ban may reduce addiction risk among younger individuals and some minoritized groups of smokers.

IMPLICATIONS

This study provides evidence of the greater relative reinforcing value of menthol compared to nonmenthol cigarettes among young adults who had a cigarette flavor preference, suggesting increased addiction risk of menthol cigarettes. Young adult menthol smokers and Hispanic (vs. non-Hispanic) smokers worked harder to earn menthol (vs. nonmenthol) cigarette puffs. Findings add to the evidence base supporting the U.S. Food and Drug Administration's (FDA) intent to ban menthol in cigarettes. Further, prevention messaging campaigns and cessation programs should take into account the reinforcing value of menthol in cigarettes, especially in vulnerable and at-risk populations.

Nicotine receptor partial agonists for smoking cessation

Background

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

Objectives

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

Search methods

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

Selection criteria

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

Data collection and analysis

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

Main results

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

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

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

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

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

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

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

Authors' conclusions

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

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

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

Key messages

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

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

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

What are 'nicotine receptor partial agonists'?

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

What did we want to find out?

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

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

· how many people had unwanted effects.

What did we do?

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

What did we find?

We found 75 studies that compared NRPAs with:

· placebo or no medicine;

· nicotine replacement therapy, such as patches or gum;

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

· another NRPA;

· e‐cigarettes.

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

Main results

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

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

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

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

What are the limitations of the evidence?

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

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

How up to date is the evidence?

The evidence is up to date to 29 April 2022.

Nicotine receptor partial agonists for smoking cessation

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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

Addictive behavior as molar behavioral allocation: Distinguishing efficient and final causes in translational research and practice

OBJECTIVE

Translational research on addictive behaviors viewed as molar behavioral allocation is critically reviewed. This work relates rates of behavior to rates of reinforcement over time and has been fruitfully applied to addictive behaviors, which involve excessive allocation to short-term rewards with longer term costs.

METHOD

Narrative critical review.

RESULTS

This approach distinguishes between final and efficient causes of discrete behaviors. The former refers to temporally extended behavior patterns into which the act fits. The latter refers to environmental stimuli or internal psychological mechanisms immediately preceding the act. Final causes are most clear when addictive behaviors are studied over time as a function of changing environmental circumstances. Discrete acts of addictive behavior are part of an extended/molar behavior pattern when immediate constraints on engagement are low and few rewarding alternatives are available. Research framed by efficient causes often use behavioral economic simulation tasks as individual difference variables that precede discrete acts. Such measures show higher demand for addictive commodities and steeper discounting in various risk groups, but whether they predict molar addictive behavior patterning is understudied.

CONCLUSIONS

Although efficient cause analysis has dominated translational research, research supports viewing addictive behavior as molar behavioral allocation. Increasing concern with rate variables underpinning final cause analysis and considering how study methods and temporal units of analysis inform an efficient or final cause analysis may advance understanding of addictive behaviors that occur over time in dynamic environmental contexts. This approach provides linkages between behavioral science and disciplines that study social determinants of health. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

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

RATIONALE

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Decreased cocaine demand following contingency management treatment

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

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

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

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

RATIONALE

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Relating individual differences in nicotine dependence severity to underpinning motivational and pharmacological processes among smokers from vulnerable populations

We examined whether elucidating underpinning smoking motivation and related pharmacological processes enhances understanding of nicotine dependence among smokers from vulnerable populations. Data were obtained between Oct, 2016 and Sept, 2019 from 745 adult smokers with co-morbid psychiatric conditions or socioeconomic disadvantage at University of Vermont, Brown University, Johns Hopkins University. Smoking motivation was assessed using the Cigarette Purchase Task (CPT), a behavioral-economic task that models the relative reinforcing value of smoking under varying monetary constraint. Dependence severity was measured using the Heaviness of Smoking Index (HSI), Fagerström Test for Nicotine Dependence total scores (FTND), and FTND total scores minus items 1 and 4 (FTND_2,3,5,6). We also assessed associations between dependence severity and smoking motivation with nicotine levels and metabolism rate. Principal Component Analysis was used to examine the latent structure of the conventional five CPT indices; bivariate and multivariable modeling was used to test associations. Factor analysis resulted in a two-factor solution, Amplitude (demand unconstrained by price) and Persistence (price sensitivity). CPT latent factors were associated with each dependence-severity measure (ps ≤ 0.0001), with associations stronger for Amplitude than Persistence across each, especially HSI which was exclusively associated with Amplitude_. Amplitude and each dependence measure were associated with nicotine intake (ps ≤ 0.0002); Persistence was not (p = .19). Demand Amplitude more than Persistence appears key to understanding individual differences in dependence severity. Regarding potential application, the results suggest a need for interventions that more effectively target demand Amplitude to make greater headway in reducing smoking in vulnerable populations. Trial Registration:clinicaltrials.gov identifiers: NCT02232737, NCT02250664, NCT02250534.

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

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

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

BACKGROUND AND AIMS

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

RESULTS

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

CONCLUSIONS

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

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

BACKGROUND ANDAIMS

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

DESIGN

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

SETTING AND PARTICIPANTS

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

MEASUREMENTS

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

FINDINGS

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

CONCLUSIONS

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

Menthol cigarette smoking is associated with greater subjective reward, satisfaction, and "throat hit", but not greater behavioral economic demand

AIMS

The cooling and minty flavor of menthol in cigarettes has been hypothesized to mask the harshness of inhaled cigarette smoke, contributing to menthol's appeal and subjective reinforcement and linking menthol use to smoking initiation, progression, nicotine dependence, and difficulty quitting. This study examined differences between menthol and non-menthol smokers on behavioral economic indices of reinforcing efficacy (i.e., demand) and subjective response to smoking (i.e., satisfaction, reward, "throat hit," aversion) and the association between measurements of reinforcement and subjective response.

DESIGN

600 current adult smokers were recruited from an online smoking cessation program. Following website enrollment, individuals completed a self-report measurement of subjective response to smoking (reward, satisfaction, aversion, "throat hit"), and a modified cigarette purchase task (CPT) to assess behavioral economic cigarette demand.

FINDINGS

In bivariate and adjusted ANOVA models, menthol smokers reported greater subjective reward, satisfaction, and positive sensations in the throat ("throat hit") from smoking compared to non-menthol smokers; and those outcomes were also correlated with greater nicotine dependence and lower likelihood of a past-year quit attempt. Although cigarette demand was associated with smoking level, subjective smoking reward, and nicotine dependence, there were no differences in smoking demand between menthol vs. non-menthol smokers.

CONCLUSIONS

The pleasurable aspects of menthol vs non-menthol smoking may be a mechanism linking it to greater nicotine dependence and difficulty quitting. A menthol ban could decrease population-level cigarette consumption by restricting smokers' access to a highly rewarding cigarette flavoring.

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

BACKGROUND AND AIMS

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

DESIGN

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

SETTING

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

PARTICIPANTS

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

MEASUREMENTS

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

FINDINGS

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

CONCLUSIONS

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

Sensitivity of hypothetical purchase task indices when studying substance use: A systematic literature review

Hypothetical Purchase Tasks (HPTs) simulate demand for a substance as a function of escalating price. HPTs are increasingly used to examine relationships between substance-related correlates and outcomes and demand typically characterized using a common battery of indices (Intensity, Omax, Pmax, Breakpoint, Elasticity). This review examines the relative sensitivity of the HPT indices. Reports were identified using the search term "purchase task" in PubMed and Web of Science. For inclusion, reports had to be original studies in English, examine relationships between HPT indices and substance-related correlates or outcomes, and appear in a peer-reviewed journal through December 2017. Indices were compared using effect sizes (Cohen's d) and the proportion of studies in which statistically significant relationships were observed. The search identified 1274 reports with 114 (9%) receiving full-text review and 82 (6%) meeting inclusion criteria. 41 reports examined alcohol, 34 examined cigarettes/nicotine products, and 10 examined other substances. Overall, statistically significant relationships between HPT indices and substance-related correlates and outcomes were most often reported for Intensity (88.61%, 70/79), followed by Omax (81.16%, 56/69), Elasticity (72.15%, 57/59), Breakpoint (62.12%, 41/66), and Pmax (48.08%; 25/52). The largest effect sizes were observed for Intensity (0.75 ± 0.04, CI 0.67-0.84) and Omax (0.64 ± 0.04, CI 0.56-0.71), followed by Elasticity (0.44 ± 0.04, CI 0.37-0.51), Breakpoint (0.30 ± 0.03, CI 0.25-0.36), and Pmax (0.25 ± 0.04, CI 0.18-0.33). Patterns were largely consistent across substances. In conclusion, HPTs can be highly effective in revealing relationships between demand and substance-related correlates and outcomes, with Intensity and Omax exhibiting the greatest sensitivity.

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

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

Behavioral Economic Research in Addiction as an Area of Growth for the Experimental Analysis of Behavior

Behavioral economics, a synthesis of the experimental analysis of behavior (EAB) and economics, seeks to determine the relative value of reinforcers as a function of various environmental constraints. Early animal and human studies often focused on drug reinforcement, and this has continued to the present. In particular, behavioral economic analyses of human and animal behavior in relation to nicotine and cigarette smoking have contributed to a greater understanding of this behavior, and to a greater reliance on these methods in the field of smoking cessation treatment, tobacco regulatory science and tobacco control. In this commentary, we briefly describe the history of behavioral economics in the context of EAB methods, the particular contribution of these methods to understanding cigarette smoking and the advance of tobacco regulation, as well as opportunities for growth and remaining challenges in this area. As behavioral economics continues to stimulate research and inform policy, we propose that the underlying elements of a rigorous analytic approach to understanding behavior are key contributors to the fruitfulness of this approach.

In-treatment cigarette demand among treatment-seeking smokers with depressive symptoms

INTRODUCTION

Despite previous evidence supporting the use of the Cigarette Purchase Task (CPT) as a valid tool for assessing smoking reinforcement, research assessing how environmental changes affect CPT performance is scarce.

AIMS

This study addressed for the first time the differential effect of treatment condition [Cognitive Behavioral Treatment (CBT) + Behavioral Activation (BA) versus CBT + BA + Contingency Management (CM)] on cigarette demand among treatment seeking smokers with depressive symptoms. It also sought to assess whether reductions in smoking consumption arranged over the course of an intervention for smoking cessation impact on in-treatment cigarette demand.

METHOD

Participants were 92 smokers with depressive symptoms from a randomized clinical trial that received eight weeks of either CBT + BA or CBT + BA + CM. Individuals completed the CPT 8 times; the first during the intake visit and the remaining 7 scheduled once a week in midweek sessions. Cotinine samples were collected in each session.

RESULTS

Participants receiving CBT + BA + CM showed higher reduction in cigarette demand across sessions than participants receiving CBT + BA, although this comparison was only significant for the intensity index (p = .004). Cotinine was positively related to cigarette demand (all p values < .001), although this association became less prominent across sessions. In-treatment cotinine decreases were associated with demand reductions (all p values < .001), but this association was not significant for elasticity.

CONCLUSIONS

Reductions in nicotine intake arranged over the course of an intervention for smoking cessation impact in-treatment cigarette demand.

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

BACKGROUND

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

METHOD

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

RESULTS

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

CONCLUSION

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

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

RATIONALE

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

TRIAL REGISTRATION

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

Simulating demand for cigarettes among pregnant women: A Low-Risk method for studying vulnerable populations

A substantive obstacle to experimentally studying cigarette smoking and use of other tobacco products in pregnant women is the risk of adverse effects on mother and fetus from experimenter administration of the product of interest. The purpose of this study is to investigate bypassing that obstacle by using behavioral economic simulation tasks. In the present study we used the Cigarette Purchase Task (CPT) to simulate changes in demand for hypothetical cigarettes as a function of varying cigarette prices. Participants were 95 pregnant women who completed the CPT prior to participation in a smoking-cessation trial. Aggregate and individual participant demand varied as an orderly function of price and those changes were well fitted by an exponential equation. Demand also varied in correspondence to two well-validated predictors of individual differences in smoking cessation among pregnant women (cigarettes smoked per day, pre-pregnancy quit attempts). Moreover, CPT indices were more effective than these two conventional variables in predicting individual differences in whether women made a quit attempt during the current pregnancy. Overall, these results represent a promising step in demonstrating the validity and utility of the CPT for experimentally examining demand for cigarettes, and potentially other tobacco and nicotine delivery products, among pregnant women.

Comparing exponential and exponentiated models of drug demand in cocaine users

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

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

INTRODUCTION

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

METHOD

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

RESULTS

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

CONCLUSIONS

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

Nicotine receptor partial agonists for smoking cessation

BACKGROUND

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

OBJECTIVES

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

SEARCH METHODS

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

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

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

MAIN RESULTS

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

AUTHORS' CONCLUSIONS

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