The neurobiological basis for partial agonist treatment of nicotine dependence: varenicline

Reduction of nicotine and ethanol intake in alcohol-preferring (UChB) female rats by the α4β2 nicotinic acetylcholine receptor partial agonists 5-bromocytisine and cytisine

RATIONALE

Neuronal nicotinic acetylcholine receptors (nAChRs) are implicated in the reinforcing effects of nicotine and ethanol. Previous studies have shown that cytisine and its 5-bromo derivative are partial agonists at the α4β2 nAChRs and that the parent molecule cytisine is effective in reducing both nicotine- and ethanol-self-administration in rats. However, whether 5-bromocytisine affects nicotine or ethanol self-administration was unknown.

OBJECTIVES

The present study compared the effects of 5-bromocytisine and cytisine on nicotine self-administration and further assessed the effect of daily drug injection on voluntary ethanol consumption in alcohol-preferring female rats. Animals were administered a 1.5mg/kg i.p. dose of 5-bromocytisine or cytisine every day for 15-16 days.

RESULTS

The initial efficacy of 5-bromocytisine and cytisine in reducing nicotine intake was similar (-80%) while for voluntary ethanol intake 5-bromocytisine was a superior inhibitor over cytisine (-78% and -40% respectively). The efficacy of cytisine began to diminish after 10 days of daily administration, which was attributed to tolerance development to its inhibitory effects both on nicotine and ethanol self-administration. Tolerance did not develop for 5-bromocytisine.

CONCLUSION

5-Bromocytisine, a weaker α4β2 nAChR partial agonist than cytisine, also produces a sustained inhibition of both nicotine and ethanol self-administration, and unlike cytisine, it does not develop tolerance.

Assessing the income-related inequality in obesity among the elderly in China: A decomposition analysis

Background

Obesity among the elderly imposes a significant health and economic burden. The purpose of this study was to measure the obesity prevalence and income-related inequality among older adults in China and to explore the determinants of the inequity.

Methods

Data were obtained from 4,541 older adults (60 years and older) participating in the China Family Panel Study, 2018. Obesity was defined as body mass index (BMI) ≥28 kg/m². Normalized concentration index and concentration curve were calculated to measure the income-related inequality. Decomposition analysis was used to measure the contribution of each factor to the overall unfairness.

Results

The prevalence of obesity among the respondents was 7.99%. The 95% confidence interval for the overall prevalence was 7.20-8.78%. The normalized concentration index of obesity in the elderly was 0.075 (95% confidence interval: 0.047-0.103), indicating that obesity was more concentrated among the rich (p < 0.05). Socioeconomic factors contributed the most to the overall inequality (68.73%). Health behavior factors explained 16.38% of the observed income-related inequality in obesity among the elderly in China.

Conclusions

In 2018, obesity was more concentrated among the elderly with higher incomes in China. The pro-poor income-related inequality was mainly due to the higher socioeconomic status of higher-income older adults. Health behaviors and psychosocial factors could also exacerbate the inequality. To prevent the heavy burden of obesity on the health and finances of older adults, more attention should be paid to those who are financially better off, especially those who smoke and are physically inactive, while extroverted older adults also need to be focused on. For developing countries, concern needs to be given to the obesity of the wealthy elderly as a result of economic development.

Exploring determinants of agonist efficacy at the CB1 cannabinoid receptor: Analogues of the synthetic cannabinoid receptor agonist EG-018

Neutral antagonists of GPCRs remain relatively rare—indeed, a large majority of GPCR antagonists are actually inverse agonists. The synthetic cannabinoid receptor agonist (SCRA) EG‐018 was recently reported as a low efficacy cannabinoid receptor agonist. Here we report a comparative characterization of EG‐018 and 13 analogues along with extant putative neutral antagonists of CB₁. In HEK cells stably expressing human CB₁, assays for inhibition of cAMP were performed by real‐time BRET biosensor (CAMYEL), G protein cycling was quantified by [³⁵S]GTPγS binding, and stimulation of pERK was characterized by AlphaLISA (PerkinElmer). Signaling outcomes for the EG‐018 analogues were highly variable, ranging from moderate efficacy agonism with high potency, to marginal agonism at lower potency. As predicted by differing pathway sensitivities to differences in ligand efficacy, most EG‐018‐based compounds were completely inactive in pERK alone. The lowest efficacy analogue in cAMP assays, 157, had utility in antagonism assay paradigms. Developing neutral antagonists of the CB₁ receptor has been a long‐standing research goal, and such compounds would have utility both as research tools and in therapeutics. Although these results emphasize again the importance of system factors in determining signaling outcomes, some compounds characterized in this study appear among the lowest efficacy agonists described to date and therefore suggest that development of neutral antagonists is an achievable goal for CB₁.

Characterising the nicotine metabolite ratio and its association with treatment choice: A cross sectional analysis of Stop Smoking Services in England

Pharmacotherapy provision based on Nicotine Metabolite Ratio (NMR) status (slow/normal metabolism) may improve smoking cessation rates. However, it is unclear whether NMR status is consistent across patient characteristics and current treatment choice. Data come from 1,826 participants attending Stop Smoking Services (SSS) across England in 2012/13. Sociodemographic, mental/physical health, smoking and treatment characteristics (nicotine replacement therapy vs. other pharmacotherapy; group vs. one-to-one behavioural support) were assessed. Salivary nicotine metabolites were measured and NMR (3-hydroxycotinine/cotinine) computed, characterising smokers as slow (NMR < 0.31) or normal (NMR ≥ 0.31) metabolisers. Normal metabolisers were older than slow metabolisers (Odds Ratio (OR) = 1.49, 95% Confidence Interval (CI) = 1.32-1.69) but no other characteristics were associated with NMR status. Overall, predictors accounted for only 7.3% of NMR variance. In adjusted analysis, pharmacotherapy type was not associated with NMR status, but normal metabolisers were less likely to use group support (OR = 0.67, 95% CI = 0.51-0.89). NMR status does not vary substantially across sociodemographic characteristics. Given its impact on pharmacotherapy efficacy, the lack of an association with pharmacotherapy choice suggests there is scope to use NMR status to optimise the selection and efficacy of smoking cessation pharmacotherapy. The unexpected association of NMR status with behavioural support should be explored further.

Healthcare financing systems for increasing the use of tobacco dependence treatment

BACKGROUND

Tobacco smoking is the leading preventable cause of death worldwide, which makes it essential to stimulate smoking cessation. The financial cost of smoking cessation treatment can act as a barrier to those seeking support. We hypothesised that provision of financial assistance for people trying to quit smoking, or reimbursement of their care providers, could lead to an increased rate of successful quit attempts. This is an update of the original 2005 review.

OBJECTIVES

The primary objective of this review was to assess the impact of reducing the costs for tobacco smokers or healthcare providers for using or providing smoking cessation treatment through healthcare financing interventions on abstinence from smoking. The secondary objectives were to examine the effects of different levels of financial support on the use or prescription of smoking cessation treatment, or both, and on the number of smokers making a quit attempt (quitting smoking for at least 24 hours). We also assessed the cost effectiveness of different financial interventions, and analysed the costs per additional quitter, or per quality-adjusted life year (QALY) gained.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group Specialised Register in September 2016.

SELECTION CRITERIA

We considered randomised controlled trials (RCTs), controlled trials and interrupted time series studies involving financial benefit interventions to smokers or their healthcare providers, or both.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed the quality of the included studies. We calculated risk ratios (RR) for individual studies on an intention-to-treat basis and performed meta-analysis using a random-effects model.

MAIN RESULTS

In the current update, we have added six new relevant studies, resulting in a total of 17 studies included in this review involving financial interventions directed at smokers or healthcare providers, or both.Full financial interventions directed at smokers had a favourable effect on abstinence at six months or longer when compared to no intervention (RR 1.77, 95% CI 1.37 to 2.28, I² = 33%, 9333 participants). There was no evidence that full coverage interventions increased smoking abstinence compared to partial coverage interventions (RR 1.02, 95% CI 0.71 to 1.48, I² = 64%, 5914 participants), but partial coverage interventions were more effective in increasing abstinence than no intervention (RR 1.27 95% CI 1.02 to 1.59, I² = 21%, 7108 participants). The economic evaluation showed costs per additional quitter ranging from USD 97 to USD 7646 for the comparison of full coverage with partial or no coverage.There was no clear evidence of an effect on smoking cessation when we pooled two trials of financial incentives directed at healthcare providers (RR 1.16, CI 0.98 to 1.37, I² = 0%, 2311 participants).Full financial interventions increased the number of participants making a quit attempt when compared to no interventions (RR 1.11, 95% CI 1.04 to 1.17, I² = 15%, 9065 participants). There was insufficient evidence to show whether partial financial interventions increased quit attempts compared to no interventions (RR 1.13, 95% CI 0.98 to 1.31, I² = 88%, 6944 participants).Full financial interventions increased the use of smoking cessation treatment compared to no interventions with regard to various pharmacological and behavioural treatments: nicotine replacement therapy (NRT): RR 1.79, 95% CI 1.54 to 2.09, I² = 35%, 9455 participants; bupropion: RR 3.22, 95% CI 1.41 to 7.34, I² = 71%, 6321 participants; behavioural therapy: RR 1.77, 95% CI 1.19 to 2.65, I² = 75%, 9215 participants.There was evidence that partial coverage compared to no coverage reported a small positive effect on the use of bupropion (RR 1.15, 95% CI 1.03 to 1.29, I² = 0%, 6765 participants). Interventions directed at healthcare providers increased the use of behavioural therapy (RR 1.69, 95% CI 1.01 to 2.86, I² = 85%, 25820 participants), but not the use of NRT and/or bupropion (RR 0.94, 95% CI 0.76 to 1.18, I² = 6%, 2311 participants).We assessed the quality of the evidence for the main outcome, abstinence from smoking, as moderate. In most studies participants were not blinded to the different study arms and researchers were not blinded to the allocated interventions. Furthermore, there was not always sufficient information on attrition rates. We detected some imprecision but we judged this to be of minor consequence on the outcomes of this study.

AUTHORS' CONCLUSIONS

Full financial interventions directed at smokers when compared to no financial interventions increase the proportion of smokers who attempt to quit, use smoking cessation treatments, and succeed in quitting. There was no clear and consistent evidence of an effect on smoking cessation from financial incentives directed at healthcare providers. We are only moderately confident in the effect estimate because there was some risk of bias due to a lack of blinding in participants and researchers, and insufficient information on attrition rates.

Emerging pharmacotherapies for alcohol use disorder

The identification of different stages within the alcohol use disorder (AUD) cycle that are linked to neurocircuitry changes in pathophysiology associated with the negative emotional states of abstinence has provided a view of medication development for AUD that emphasizes changes in the brain reward and stress systems. Alcohol use disorder can be defined as a chronic relapsing disorder that involves compulsive alcohol seeking and taking, loss of control over alcohol intake, and emergence of a negative emotional state during abstinence. The focus of early medications development was to block the motivation to seek alcohol in the binge/intoxication stage. More recent work has focused on reversing the motivational dysregulations associated with the withdrawal/negative affect and preoccupation/anticipation stages during protracted abstinence. Advances in our understanding of the neurocircuitry and neuropharmacological mechanisms that are involved in the development and maintenance of the withdrawal/negative affect stage using validated animal models have provided viable targets for future medications. Another major advance has been proof-of-concept testing of potential therapeutics and clinical validation of relevant pharmacological targets using human laboratory models of protracted abstinence. This review focuses on future targets for medication development associated with reversal of the loss of reward function and gain in brain stress function that drive negative reinforcement in the withdrawal/negative affect stage of addiction. Basic research has identified novel neurobiological targets associated with the withdrawal/negative affect stage and preoccupation/anticipation stage, with a focus on neuroadaptive changes within the extended amygdala that account for the transition to dependence and vulnerability to relapse. This article is part of the Special Issue entitled "Alcoholism".

Oral Varenicline for Smoking Cessation

Objective:

To review the pharmacology, pharmacokinetics, efficacy, and safety of varenicline and provide a review of relevant clinical data.

Data Sources:

A MEDLINE search (2001–December 2006) was conducted using the key words varenicline and nicotine replacement therapy for clinical trials limited to human subjects and published in English.

Study Selection And Data Extraction:

All available human trials of varenicline were selected for review. References cited in identified articles were used for additional citations.

Data Synthesis:

Varenicline selectively targets the α4β2 nicotine receptors in the brain that are responsible for cravings and withdrawal associated with nicotine use and dependence. Maximal plasma concentration occurs within 3–4 hours after administration and, after multiple doses, a steady-state concentration is reached within 4 days. Varenicline has a half-life of 24 hours. Oral bioavailability is not affected by food or time of administration. It exhibits linear pharmacokinetics and tow plasma protein binding (≤20%) regardless of a patient's age and renal status. It can be administered once daily. Dosage adjustments are not required in patients with hepatic insufficiency, but adjustments may be necessary in patients with severe renal insufficiency. Clinically significant drug–drug interactions have not been observed with varenicline or co-inhibitors of the human organic cation transporter, which mediates renal secretion of varenicline. Substrates such as warfarin, digoxin, cimetidine, metformin, bupropion, and transdermal nicotine do not alter pharmacokinetic parameters when coadministered with varenicline. In vitro studies have not demonstrated alterations in cytochrome P450 enzyme parameters. Varenicline's safety with coadministration of nicotine replacement products has not been well established.

Conclusions:

Varenicline is an effective oral agent for smoking cessation.

l-tetrahydropalmatine reduces nicotine self-administration and reinstatement in rats

BACKGROUND

The negative consequences of nicotine use are well known and documented, however, abstaining from nicotine use and achieving abstinence poses a major challenge for the majority of nicotine users trying to quit. l-Tetrahydropalmatine (l-THP), a compound extracted from the Chinese herb Corydalis, displayed utility in the treatment of cocaine and heroin addiction via reduction of drug-intake and relapse. The present study examined the effects of l-THP on abuse-related effects of nicotine.

METHODS

Self-administration and reinstatement testing was conducted. Rats trained to self-administer nicotine (0.03 mg/kg/injection) under a fixed-ratio 5 schedule (FR5) of reinforcement were pretreated with l-THP (3 or 5 mg/kg), varenicline (1 mg/kg), bupropion (40 mg/kg), or saline before daily 2-h sessions. Locomotor, food, and microdialysis assays were also conducted in separate rats.

RESULTS

l-THP significantly reduced nicotine self-administration (SA). l-THP's effect was more pronounced than the effect of varenicline and similar to the effect of bupropion. In reinstatement testing, animals were pretreated with the same compounds, challenged with nicotine (0.3 mg/kg, s.c.), and reintroduced to pre-extinction conditions. l-THP blocked reinstatement of nicotine seeking more effectively than either varenicline or bupropion. Locomotor data revealed that therapeutic doses of l-THP had no inhibitory effects on ambulatory ability and that l-THP (3 and 5 mg/kg) significantly blocked nicotine induced hyperactivity when administered before nicotine. In in-vivo microdialysis experiments, l-THP, varenicline, and bupropion alone elevated extracellular dopamine (DA) levels in the nucleus accumbens shell (nAcb).

CONCLUSIONS

Since l-THP reduces nicotine taking and blocks relapse it could be a useful alternative to varenicline and bupropion as a treatment for nicotine addiction.

Varenicline: A Novel Nicotinic Receptor Partial Agonist for Smoking Cessation

Objective:

To review the pharmacology, pharmacokinetics, clinical efficacy, and safety of varenicline, a selective partial nicotinic receptor agonist for smoking cessation.

Data Sources:

Primary literature and review articles were obtained via a MEDLINE search (1966–January 2007) using the key terms smoking cessation, nicotinic receptor, tobacco, and varenicline. Additional studies and abstracts were identified from the bibliographies of reviewed literature.

Study Selection and Data Extraction:

Available English-language literature, including abstracts, preclinical and clinical trials, and review articles were identified. Six randomized, placebo-controlled trials were evaluated to determine varenicline's efficacy for smoking cessation.

Data Synthesis:

Varenicline is a partial agonist selective for the α4β2 nicotinic receptor. Varenicline has been compared with placebo and sustained-release (SR) bupropion in randomized, double-blind, controlled trials. These trials found varenicline to have more successful 4 week continuous quit rates compared with both placebo and bupropion SR. One study reported a significantly increased continuous abstinence rate with varenicline versus bupropion SR; however, 2 other studies found no difference between varenicline and bupropion SR. To date, dose-dependent nausea is the most frequent adverse effect associated with varenicline; this may be limited with proper dosage titration.

Conclusions:

Increased cessation rates in comparison with placebo and, possibly, bupropion SR, as well as limited safety concerns, suggest that varenicline may have a role as another first-line therapy for smoking cessation.

Varenicline and Adverse Cardiovascular Events: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Background

Varenicline is an efficacious smoking‐cessation drug. However, previous meta‐analyses provide conflicting results regarding its cardiovascular safety. The publication of several new randomized controlled trials (RCTs) provides an opportunity to reassess this potential adverse drug reaction.

Methods and Results

We searched MEDLINE, EMBASE, and the Cochrane Library for RCTs that compare varenicline with placebo for smoking cessation. RCTs reporting cardiovascular serious adverse events and/or all‐cause mortality during the treatment period or within 30 days of treatment discontinuation were eligible for inclusion. Relative risks (RRs) with 95% CIs were generated by using DerSimonian–Laird random‐effects models. Thirty‐eight RCTs met our inclusion criteria (N=12 706). Events were rare in both varenicline (57/7213) and placebo (43/5493) arms. No difference was observed for cardiovascular serious adverse events when comparing varenicline with placebo (RR 1.03, 95% CI 0.72–1.49). Similar findings were obtained when examining cardiovascular (RR 1.04, 95% CI 0.57–1.89) and noncardiovascular patients (RR 1.03, 95% CI 0.64–1.64). Deaths were rare in both varenicline (11/7213) and placebo (9/5493) arms. Although 95% CIs were wide, pooling of all‐cause mortality found no difference between groups (RR 0.88, 95% CI 0.50–1.52), including when stratified by participants with (RR 1.24, 95% CI 0.40–3.83) and without (RR 0.77, 95% CI 0.40–1.48) cardiovascular disease.

Conclusions

We found no evidence that varenicline increases the rate of cardiovascular serious adverse events. Results were similar among those with and without cardiovascular disease. Given varenicline's efficacy as a smoking cessation drug and the long‐term cardiovascular benefits of cessation, it should continue to be prescribed for smoking cessation.

CYP2A6 Polymorphisms May Strengthen Individualized Treatment for Nicotine Dependence

Each CYP2A6 gene variant metabolizes nicotine differently depending on its enzymatic activities. The normal nicotine metabolizer CYP2A6(*)1A is associated with high scores of nicotine dependence (5-10) on the Fagerström Test for Nicotine Dependence (FTND) scale because it encodes for enzymes that catalyze nicotine 100%. Slow nicotine metabolizers (i.e., CYP2A6(*)1H, CYP2A6(*)4A, CYP2A6(*)9, and CYP2A6(*)12A) are associated with underrated nicotine metabolizing activity (50%-75%), linking them to low scores for nicotine dependence (0-4) on the FTND scale. In a clinical trial involving the use of bupropion, people who were carriers of slow nicotine metabolizers were found to have a tendency to maintain abstinence 1.7 times longer than people with normal nicotine metabolizers. An overview of CYP2A6 polymorphism enzymatic activities in nicotine dependence etiology and treatment revealed that slow nicotine metabolizers may strengthen the individualized treatment of nicotine dependence.

Differentiating the primary reinforcing and reinforcement-enhancing effects of varenicline

RATIONALE

Varenicline (VAR), a smoking cessation aid that is a partial agonist at nicotinic receptors, mimics the reinforcement-enhancing effects of nicotine. Varenicline, when accompanied by non-drug cues, is self-administered by rats, though it is unclear whether this results from varenicline acting as a primary reinforcer or a reinforcement enhancer of the cues.

OBJECTIVES

This study sought to disentangle these two potential actions.

METHODS

Rats were allowed to self-administer intravenous nicotine, saline, or varenicline during 1-h sessions in operant chambers equipped with two levers. Five groups had concurrent access to drug infusions and a moderately reinforcing visual stimulus (VS) for responding on separate levers. Meeting the reinforcement schedule on one lever was reinforced with VAR (0.01, 0.06, 0.1 mg/kg/infusion), nicotine (0.06 mg/kg/infusion), or saline, while meeting the same schedule on the other lever delivered the VS. Additional groups were reinforced for pressing a single "active" lever and received VAR paired with the VS, the VS with response-independent infusions of VAR, or VAR alone (0.1 mg/kg/infusion).

RESULTS

Rats readily responded for VAR paired with VS on a single lever. However, when VAR was the only reinforcer contingent on a response, rats did not respond more than for saline.

CONCLUSIONS

These findings show that VAR does not serve as a primary reinforcer in rats at doses that increase responding for non-drug reinforcers. These data are consistent with research showing that the primary reinforcing effects of VAR are weak, at best, and that the primary reinforcing and reinforcement-enhancing actions of nicotinic drugs are pharmacologically distinct.

Pharmacological Options for Smoking Cessation in Heavy-Drinking Smokers

There is a high prevalence of comorbid tobacco use and alcohol use disorder (AUD), affecting more than 6 million people in the US. Globally, tobacco and alcohol use rank fourth and fifth, respectively, for disability-adjusted life-years lost. Levels of alcohol use are higher in smokers than nonsmokers, and the prevalence of smoking is higher in heavy drinkers compared with nondrinkers. This relationship is driven by many different factors, including genetics, neurobiological mechanisms, conditioning processes, and psychosocial influences. Although this unique population tends to experience more negative health consequences, more severe AUD, and poorer response to treatment than those with either AUD or tobacco use disorder alone, there are currently no available treatment protocols tailored to this comorbid condition. In this review, we provide a comprehensive review of ongoing clinical research into smoking cessation options for heavy-drinking smokers (HDS) through an evaluation of the effect of promising novel pharmacotherapies as well as combination therapies, including varenicline, naltrexone, the combination of varenicline and naltrexone, and the combination of naltrexone and nicotine replacement therapy (NRT). These treatments are considered in light of the standard of care for smoking cessation, and seek to improve upon the available guidelines for this sizeable subgroup of smokers, namely those smokers who drink heavily.

The cytisine derivatives, CC4 and CC26, reduce nicotine-induced conditioned place preference in zebrafish by acting on heteromeric neuronal nicotinic acetylcholine receptors

RATIONALE

Cigarette smoking is one of the most serious health problems worldwide and people trying to stop smoking have high rates of relapse. Zebrafish (Danio rerio), by combining pharmacological and behavioral assays, is a promising animal model for rapidly screening new compounds to induce smoking cessation.

OBJECTIVES

This study aims to identify possible acetylcholine nicotinic receptors (nAChRs) involved in mediating nicotine (NIC)-induced conditioned place preference (CPP) in zebrafish and investigate the effect of the CC4 and CC26 cytisine derivatives in reducing NIC-induced CPP.

METHODS

CPP was evaluated using a two-compartment chamber, and the zebrafish were given CC4 (0.001-5 mg/kg), CC26 (0.001-1 mg/kg), cytisine (0.1-2.5 mg/kg), and varenicline (1-10 mg/kg) alone or with NIC (0.001 mg/kg). Swimming activity was evaluated using a square observational chamber. The affinity of the nicotinic ligands for native zebrafish brain nAChRs was evaluated by binding studies using [(3)H]-Epibatidine (Epi) and [(125)I]-αBungarotoxin (αBgtx) radioligands, and their subtype specificity was determined by means of electrophysiological assay of oocyte-expressed α4β2 and α7 subtypes.

RESULTS

CC4 and CC26 induced CPP with an inverted U-shaped dose-response curve similar to that of NIC. However, when co-administered with NIC, they blocked its reinforcing or slightly aversive effect. Binding and electrophysiological studies showed that this effect was due to binding to high-affinity heteromeric but not α7-containing receptors.

CONCLUSIONS

We have further characterized CC4 and identified a new compound (CC26) that may be active in inducing smoking cessation. Zebrafish is a very useful model for screening new compounds that can affect the rewarding properties of NIC.

Varenicline-induced acute dystonic reaction: a case report

Dystonia is a syndrome characterized by sustained muscle contractions frequently causing twisting and repetitive movements or abnormal postures. Dystonic reactions may be a complication of many drugs such as antipsychotics, anti-emetics and antidepressants. This report presents a 25-year-old patient who was admitted to an emergency department with acute dystonia following the use of varenicline, a pharmacological agent used for the treatment of nicotine addiction. Dystonic reactions may be related to the dopaminergic deficiency caused by the use of varenicline. In conclusion, this report suggests that varenicline can cause dystonic reaction in at least some patients.

Varenicline for smoking cessation: A review of the literature

BACKGROUND

Smoking is the leading preventable risk to human health. Various agents have been used to promote smoking cessation, but none has had long-term efficacy. Varenicline, a new nicotinic ligand based on the structure of cytosine, was approved by the US Food amd Drug Administration for use as a smoking cessation aid.

OBJECTIVES

The aims of this review were to provide an overview on the mechanism of action and preclinical and clinical data of the new drug, varenicline, and to discuss the current and future impact of varenicline as a treatment for smoking cessation.

METHODS

MEDLINE, BIOSIS, and Google scholar databases were searched (March 1, 2007-July 1, 2008) using the terms varenicline, smoking cessation, and nicotinic receptors. Full-text articles in English were selected for reference, and articles presenting the mechanism of action, pharmacokinetics, and data from preclinical and clinical trials were included.

RESULTS

The initial literature search yielded 70 papers. A total of 20 articles fulfilled the inclusion criteria. Varenicline, an α4β2 nicotinic acetylcholine receptor partial agonist, inhibits dopaminergic activation produced by smoking and decreases the craving and withdrawal syndrome that accompanies cessation attempts. In Phase III clinical trials, the carbon monoxide-confirmed 4-week continuous abstinence rates were significantly higher with varenicline than with buproprion sustained release or placebo for weeks 9 through 12. Varenicline has been found to be well tolerated, with nausea being the most commonly reported (28.1%) adverse event.

CONCLUSIONS

Varenicline is the first drug for smoking cessation that has been found to have significant effectiveness in long-term relapse prevention (up to 52 weeks). Varenicline, with its unique profile of agonist and antagonist properties, increased cessation rates (both short- and long-term) compared with both placebo and bupropion sustained release.

Paradise Lost: The relationships between neurological and psychological changes in nicotine-dependent patients

The neural reward circuit and cognitive distortion play an important role in addiction; however, the relationship between the two has not yet been addressed. In this article, we review recent findings on nicotine dependence and propose a novel hypothesis. Previous research using functional magnetic resonance imaging (fMRI) has shown that while activation of the reward circuit (ventral striatum) appears in response to tobacco-related rewards in nicotine dependence, responses to rewards other than tobacco (e.g. food and money) are reduced. Moreover, this change is observed at the very early stages of smoking, even when a person has smoked fewer than 10 cigarettes in his/her lifetime. Thus, we propose the following hypothesis, called the Paradise Lost theory: given addicts' lower ventral striatal responses to non-tobacco rewards, nicotine addiction disables smokers from sensing the pleasures of ordinary life (the Paradise Lost state). However, since smokers do not notice this, they produce an overestimation of tobacco (cognitive distortion), such that they do not have many pastimes other than smoking or feel that quitting smoking would reduce the happiness and pleasure and increase the difficulty of life. Cognitive distortion thus makes it difficult for smokers to take the initiative to quit smoking and even causes relapse after smoking cessation. This theory furthers our understanding of addiction and could improve our approach to the prevention and treatment of addiction.

Varenicline for smoking cessation

Varenicline is a selective alpha(4)beta(2) nicotinic acetylcholine receptor partial agonist and the first non-nicotine-containing medication developed with the sole purpose of treating nicotine addiction. To date, four published clinical trials have demonstrated the efficacy and safety of varenicline for smoking cessation in healthy adults who were ready to make a quit attempt. One additional trial found that extended use of varenicline effectively reduced relapse to smoking. One trial to date published as a poster documented the 1-year safety of the drug. Varenicline was more efficacious than bupropion 24 weeks after randomization to a 12-week treatment course and 1 year after randomization in an identical trial. It has no contraindications except hypersensitivity and is well tolerated. This article reviews the available information on varenicline and discusses its clinical use.

Safety of varenicline in patients with cardiovascular disease

Smoking cessation lowers the risk of death substantially in patients with cardiovascular disease. Although varenicline is an effective medication for smoking cessation, its safety in this population has been questioned and evaluated in several studies. In 2 randomized controlled trials of patients with cardiovascular disease, the rates of serious cardiovascular events were up to 2% higher in patients receiving varenicline than placebo, though the differences were not statistically significant. In the first meta-analysis of mostly trials involving patients with a history of cardiovascular disease, varenicline was found to significantly increase the risk of cardiovascular events by 72%; however, a second meta-analysis did not find a significant increased risk. In an observational study, varenicline was not associated with an increased risk of events when compared to bupropion in a subgroup analysis of patients with a history of cardiovascular disease. Because the evidence on the safety of varenicline in this population is limited and conflicting, additional data are needed to formulate stronger conclusions. In the meantime, health care professionals should consider individual smoking patterns, concomitant medical conditions, and cost when recommending smoking cessation pharmacotherapy for patients with cardiovascular disease.

CC4, a dimer of cytisine, is a selective partial agonist at α4β2/α6β2 nAChR with improved selectivity for tobacco smoking cessation

BACKGROUND AND PURPOSE

Many of the addictive and rewarding effects of nicotine are due to its actions on the neuronal nicotinic ACh receptor (nAChR) subtypes expressed in dopaminergic mesocorticolimbic cells. The partial agonists, cytisine and varenicline, are helpful smoking cessation aids. These drugs have a number of side effects that limit their usefulness. The aim of this study was to investigate the preclinical pharmacology of the cytisine dimer1,2-bisN-cytisinylethane (CC4).

EXPERIMENTAL APPROACH

The effects of CC4 on nAChRs were investigated using in vitro assays and animal behaviours.

KEY RESULTS

When electrophysiologically tested using heterologously expressed human subtypes, CC4 was less efficacious than cytisine on neuronal α4β2, α3β4, α7 and muscle-type receptors, and had no effect on 5-hydroxytryptamine3 receptors. Acting through α4β2 and α6β2 nAChRs, CC4 is a partial agonist of nAChR-mediated striatal dopamine release and, when co-incubated with nicotine, prevented nicotine's maximal effect on this response. In addition, it had low affinity for, and was less efficacious than nicotine and cytisine on the α3β4 and α7-nAChR subtypes. Like cytisine and nicotine, CC4-induced conditioned place preference (CPP), and its self-administration shows an inverted-U dose-response curve. Pretreatment with non-reinforcing doses of CC4 significantly reduced nicotine-induced self-administration and CPP without affecting motor functions.

CONCLUSION AND IMPLICATIONS

Our in vitro and in vivo findings reveal that CC4 selectively reduces behaviours associated with nicotine addiction consistent with the partial agonist selectivity of CC4 for β2-nAChRs. The results support the possible development of CC4 or its derivatives as a promising drug for tobacco smoking cessation.

Healthcare financing systems for increasing the use of tobacco dependence treatment

BACKGROUND

We hypothesized that provision of financial assistance for smokers trying to quit, or reimbursement of their care providers, could lead to an increased rate of successful quit attempts.

OBJECTIVES

The primary objective of this review was to assess the impact of reducing the costs of providing or using smoking cessation treatment through healthcare financing interventions on abstinence from smoking. The secondary objectives were to examine the effects of different levels of financial support on the use and/or prescription of smoking cessation treatment and on the number of smokers making a quit attempt.

SEARCH METHODS

We searched the Cochrane Tobacco Addiction Group Specialized Register in April 2012.

SELECTION CRITERIA

We considered randomised controlled trials (RCTs), controlled trials and interrupted time series studies involving financial benefit interventions to smokers or their healthcare providers or both.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and assessed the quality of the included studies. Risk ratios (RR) were calculated for individual studies on an intention-to-treat basis and meta-analysis was performed using a random-effects model. We included economic evaluations when a study presented the costs and effects of two or more alternatives.

MAIN RESULTS

We found eleven trials involving financial interventions directed at smokers and healthcare providers.Full financial interventions directed at smokers had a statistically significant favourable effect on abstinence at six months or greater when compared to no intervention (RR 2.45, 95% CI 1.17 to 5.12, I² = 59%, 4 studies). There was also a significant effect of full financial interventions when compared to no interventions on the number of participants making a quit attempt (RR 1.11, 95% CI 1.04 to 1.32, I² = 15%) and use of smoking cessation treatment (NRT: RR 1.83, 95% CI 1.55 to 2.15, I² = 43%; bupropion: RR 3.22, 95% CI 1.41 to 7.34, I² = 71%; behavioural therapy: RR 1.77, 95% CI 1.19 to 2.65). There was no evidence of an effect on smoking cessation when we pooled two trials of financial incentives directed at healthcare providers (RR 1.16, CI 0.98 to 1.37, I² = 0%). Comparisons of full coverage with partial coverage, partial coverage with no coverage, and partial coverage with another partial coverage intervention did not detect significant effects. Comparison of full coverage with partial or no coverage resulted in costs per additional quitter ranging from $119 to $6450.

AUTHORS' CONCLUSIONS

Full financial interventions directed at smokers when compared to no financial interventions increase the proportion of smokers who attempt to quit, use smoking cessation treatments, and succeed in quitting.  The absolute differences are small but the costs per additional quitter are low to moderate. We did not detect an effect on smoking cessation from financial incentives directed at healthcare providers. The methodological qualities of the included studies need to be taken into consideration when interpreting the results.

Molecular actions of smoking cessation drugs at α4β2 nicotinic receptors defined in crystal structures of a homologous binding protein

Partial agonists of the α4β2 nicotinic acetylcholine receptor (nAChR), such as varenicline, are therapeutically used in smoking cessation treatment. These drugs derive their therapeutic effect from fundamental molecular actions, which are to desensitize α4β2 nAChRs and induce channel opening with higher affinity, but lower efficacy than a full agonist at equal receptor occupancy. Here, we report X-ray crystal structures of a unique acetylcholine binding protein (AChBP) from the annelid Capitella teleta, Ct-AChBP, in complex with varenicline or lobeline, which are both partial agonists. These structures highlight the architecture for molecular recognition of these ligands, indicating the contact residues that potentially mediate their molecular actions in α4β2 nAChRs. We then used structure-guided mutagenesis and electrophysiological recordings to pinpoint crucial interactions of varenicline with residues on the complementary face of the binding site in α4β2 nAChRs. We observe that residues in loops D and E are molecular determinants of desensitization and channel opening with limited efficacy by the partial agonist varenicline. Together, this study analyzes molecular recognition of smoking cessation drugs by nAChRs in a structural context.

Risk of cardiovascular serious adverse events associated with varenicline use for tobacco cessation: systematic review and meta-analysis

OBJECTIVE

To examine the risk of treatment emergent, cardiovascular serious adverse events associated with varenicline use for tobacco cessation.

DESIGN

Meta-analysis comparing study effects using four summary estimates.

DATA SOURCES

Medline, Cochrane Library, online clinical trials registries, and reference lists of identified articles.

REVIEW METHODS

We included randomised controlled trials of current tobacco users of adult age comparing use of varenicline with an inactive control and reporting adverse events. We defined treatment emergent, cardiovascular serious adverse events as occurring during drug treatment or within 30 days of discontinuation, and included any ischaemic or arrhythmic adverse cardiovascular event (myocardial infarction, unstable angina, coronary revascularisation, coronary artery disease, arrhythmias, transient ischaemic attacks, stroke, sudden death or cardiovascular related death, or congestive heart failure).

RESULTS

We identified 22 trials; all were double blinded and placebo controlled; two included participants with active cardiovascular disease and 11 enrolled participants with a history of cardiovascular disease. Rates of treatment emergent, cardiovascular serious adverse events were 0.63% (34/5431) in the varenicline groups and 0.47% (18/3801) in the placebo groups. The summary estimate for the risk difference, 0.27% (95% confidence interval -0.10 to 0.63; P = 0.15), based on all 22 trials, was neither clinically nor statistically significant. For comparison, the relative risk (1.40, 0.82 to 2.39; P = 0.22), Mantel-Haenszel odds ratio (1.41, 0.82 to 2.42; P = 0.22), and Peto odds ratio (1.58, 0.90 to 2.76; P = 0.11), all based on 14 trials with at least one event, also indicated a non-significant difference between varenicline and placebo groups.

CONCLUSIONS

This meta--analysis--which included all trials published to date, focused on events occurring during drug exposure, and analysed findings using four summary estimates-found no significant increase in cardiovascular serious adverse events associated with varenicline use. For rare outcomes, summary estimates based on absolute effects are recommended and estimates based on the Peto odds ratio should be avoided.

Varenicline dose dependently enhances responding for nonpharmacological reinforcers and attenuates the reinforcement-enhancing effects of nicotine

INTRODUCTION

Varenicline (VAR), a partial nicotinic agonist, is one of the most effective smoking cessation pharmacotherapies. The therapeutic efficacy of VAR could be partly the result of substituting for and/or blocking the reinforcement-enhancing effects of nicotine (NIC). We assessed the effects of VAR alone and in combination with NIC (0.4 mg/kg) while rats pressed the lever for a moderately reinforcing visual stimulus (VS).

METHODS

Rats were injected with placebo (0.9% saline), NIC, VAR (0.1-1 mg/kg), or NIC + VAR. A follow-up study was conducted with a broader dose range of VAR-alone dosages (0.01-3.0 mg/kg). All drug manipulations were conducted in a between-subjects design to prevent confounding effects of repeated exposure.

RESULTS

There was a dose-dependent effect of VAR alone. Moderate doses of VAR (0.1 and 1.0 mg/kg) increased the number of VS presentations earned, while lower and higher VAR doses (0.01 and 3.0 mg/kg) did not change responding for the VS. VAR dose dependently attenuated the reinforcement-enhancing effects of NIC, with the highest dose (1.0 mg/kg) exhibiting the greatest antagonist effect.

CONCLUSIONS

The results of these studies support the assertion that the therapeutic efficacy of VAR may be due to the partial agonist characteristics of the drug, specifically, its ability to partially replace the reinforcement-enhancing effects of NIC as well as antagonize these effects.

Effects of menthol on the pharmacokinetics of bupropion among Black smokers

INTRODUCTION

Despite the widespread use of mentholated cigarettes, lower cessation rates, and disproportionately high smoking-related morbidity among Blacks, the possible role of menthol in smokers' response to pharmacotherapy has not been well-studied. This study examined the effects of menthol on the pharmacokinetic (PK) profiles of bupropion and its principal metabolites, hydroxybupropion, threohydrobupropion, and erythrohydrobupropion among Black smokers.

METHODS

After a 7-day placebo run-in period, participants received 150 mg bid sustained-release bupropion for 20-25 days. Blood samples were drawn for PK analysis on 2 occasions, 10-15 days after the commencement of bupropion while participants were still smoking (smoking phase) and at days 20-25 when they were asked not to smoke (nonsmoking phase).

RESULTS

18 smokers of nonmenthol cigarettes and 23 smokers of menthol cigarettes were enrolled in this study. No differences were found by menthol smoking status in the Cmax and area under the plasma concentration versus time curve (AUC) of bupropion and its metabolites in the smoking or nonsmoking phases. However, among menthol smokers, the AUC ratios of metabolite/bupropion were lower in the nonsmoking phase compared with the smoking phase (hydro/bup = 31.49 ± 18.84 vs. 22.95 ± 13.27, p = .04; erythro/bup = 1.99 ± 1.02 vs. 1.76 ± 0.75, p = .016; threo/bup = 11.77 ± 8.90 vs. 10.44 ± 5.63, p = .034). No significant differences were found in the metabolite/bup ratios between smoking and nonsmoking conditions among nonmenthol smokers.

CONCLUSIONS

We did not find a significant effect of menthol compared with nonmenthol cigarette smoking on the PKs of bupropion and metabolites at steady state. More research is needed to advance the understanding of mechanisms underlying disparities in smoking cessation outcomes related to smoking of menthol cigarettes.

Varenicline as a smoking cessation aid in schizophrenia: effects on smoking behavior and reward sensitivity

RATIONALE

Smoking rates are up to five times higher in people with schizophrenia than in the general population, placing these individuals at high risk for smoking-related health problems. Varenicline, an α4β2 nicotinic acetylcholine receptor partial agonist, is a promising aid for smoking cessation in this population. To maximize treatment efficacy while minimizing risks, it is critical to identify reliable predictors of positive response to varenicline in smokers with schizophrenia.

OBJECTIVES

Negative symptoms of schizophrenia are related to dysfunctions in the brain reward system, are associated with nicotine dependence, and may be improved by nicotine or nicotinic receptor agonists, suggesting that smoking cessation may be especially difficult for patients with substantial negative symptoms. The purpose of the study was to evaluate negative symptoms as predictors of response to varenicline.

METHODS

Patients with schizophrenia (N = 53) completed a 12-week smoking cessation trial combining varenicline with cognitive behavioral therapy. Negative symptoms were assessed via the Scale for the Assessment of Negative Symptoms (Andreasen 1983). Outcomes included smoking abstinence as assessed by self-report and expired carbon monoxide. Change in performance on a probabilistic reward task was used as an index of change in reward sensitivity during treatment.

RESULTS

At week 12, 32 participants met criteria for 14-day point-prevalence abstinence. Patients with lower baseline symptoms of affective flattening (more typical affect) were more likely to achieve smoking abstinence and demonstrated larger increases in reward sensitivity during treatment.

CONCLUSIONS

These data suggest that affective flattening symptoms in smokers with schizophrenia may predict response to varenicline.

How do we safely get people to stop smoking?

Nicotine replacement therapy (NRT) is a valuable, proven, and U.S. Food and Drug Administration-approved tool for smoking cessation. However, the discoveries of functional nicotinic acetylcholine receptors (nAChR) on lung epithelial and cancer cells and of nAChR polymorphisms associated with lung cancer risk, in addition to a large number of preclinical studies indicating that nicotine may promote or facilitate cancer development and growth, have prompted concern that NRT, although important for smoking cessation, may actually augment lung carcinogenesis. Therefore, it is of great public health interest that two independent studies reported in this issue of the journal (Murphy and colleagues, beginning on page 1752, and Maier and colleagues, beginning on page 1743) showed that nicotine given in drinking water at a dose to achieve blood concentrations in mice similar to those achieved in people receiving NRT did not enhance lung carcinogenesis or tumor growth in several mouse models of lung cancer. Effective non-nicotine alternatives to NRT, such as varenicline and bupropion, are also available and perhaps better than NRT for smoking cessation therapy. In the near future, nicotine vaccines will likely be added to the smoking cessation armamentarium. However, the normal and pathophysiologic role of nicotine, nAChRs, and the signaling pathways they activate in lung epithelial cells and lung cancer still requires elucidation.

Induced psychosis after withdrawal of varenicline: a case report

López Arteaga MT, Amo C, Sánchez Morla EM, Sánchez Román M. Induced psychosis after withdrawal of varenicline: a case report.

Objective: Varenicline has been associated with psychiatric side effects, and cases with psychotic symptoms during treatment have been reported, few of them after the withdrawal. We describe a case with no current or previous medical or psychiatric history.

Method: A single case report.

Results: The patient without previous psychiatric pathology, following the withdrawal of treatment with varenicline, experiences delirium and behavioural disturbances. There was a remission of symptoms after 3 weeks of treatment with risperidone.

Conclusion: Discontinuation of treatment with varenicline due to poor tolerance for side effects (nausea and insomnia) could trigger psychotic symptoms in subjects with no personal or family psychiatric history.

Gastrointestinal adverse effects of varenicline at maintenance dose: a meta-analysis

Background

Tobacco smoking remains the leading modifiable health hazard and varenicline is amongst the most popular pharmacological options for smoking cessation. The purpose of this study is to critically evaluate the extent of gastrointestinal adverse effects of varenicline when used at maintenance dose (1 mg twice a day) for smoking cessation.

Methods

We conducted a meta-analysis of randomised controlled trials published in PUBMED and EMBASE according to the PRISMA guidelines. Selected studies satisfied the following criteria: (i) duration of at least 6 weeks, (ii) titrated dose of varenicline for 7 days then a maintenance dose of 1 mg twice-per-day, (iii) randomized placebo-controlled design, (iv) extractable data on adverse event - nausea, constipation or flatulence. Data was synthesized into pooled odd ratios (OR) basing on random effects model. Quality of studies was also rated as per Cochrane risk-of-bias assessment. Number need to harm (NNH) was calculated for each adverse effect.

Results

98 potentially relevant studies were identified, 12 of which met the final inclusion criteria (n = 5114). All 12 studies reported adverse events on nausea, which led to an OR of 4.45 (95% CI = 3.79-5.23, p < 0.001; I² = 0.06%, CI = 0%-58.34%) and a NNH of 5. Eight studies (n = 3539) contain data on constipation pooled into an OR of 2.45 (95% CI = 1.61-3.72, p < 0.001; I² = 34.09%, CI = 0%-70.81%) with a NNH of 24. Finally, five studies (n = 2516) reported adverse events of flatulence, which pooled an OR of 1.74 (95% CI = 1.23-2.48, p = 0.002; I² = 0%, CI = 0%- 79.2%) with a NNH of 35.

Conclusions

Use of varenicline at maintenance dose of 1 mg twice a day for longer than 6 weeks is associated with adverse gastrointestinal effects. In realistic terms, for every 5 treated subjects, there will be an event of nausea, and for every 24 and 35 treated subjects, we will expect an event of constipation and flatulence respectively. Family physicians should counsel patients of such risks accordingly during their maintenance therapy with varenicline.

Pharmacotherapeutic management of nicotine dependence in pregnancy

Smoking in pregnancy can cause serious adverse antenatal and postnatal morbidities, and a significant number of women continue to smoke in pregnancy despite these consequences. Early intervention in the form counseling from their physicians, pregnancy-specific self-help materials, counseling sessions with a health educator, and/or continued follow-up can result in better pregnancy outcomes and possibly long-term cessation. If a woman cannot quit despite these measures, pharmacotherapy can be considered. Currently, nicotine replacement therapy (NRT), transdermal patches, and bupropion are used in pregnancy, but data on the safety and efficacy are largely lacking.

Tabagismo em universitários de ciências da saúde: prevalência e conhecimento

OBJETIVO: Determinar a prevalência de tabagismo e o nível de conhecimento acerca do tabagismo entre estudantes universitários da área de saúde. MÉTODOS: Estudo transversal. Um questionário estruturado e autoadministrado foi respondido em sala de aula por universitários do último ano dos cursos da saúde de Cuiabá e Várzea Grande (MT). Foram avaliados alunos de uma universidade pública e de duas universidades particulares. Cinco variáveis foram analisadas: idade, sexo, curso de graduação, status tabágico e noções sobre o tabagismo. A variável "conhecimento" foi dividida em cinco partes: tabagismo como doença; tabagismo e nicotina como causa de dependência; treinamento específico sobre tabagismo; fatores dificultadores da cessação tabágica; e formas de tratamento do tabagismo. Os últimos dois itens somente foram respondidos pelos alunos dos cursos de medicina. RESULTADOS: A prevalência do tabagismo variou de 9,3% na universidade pública a 21,1% em uma das universidades particulares. Aproximadamente 30% dos entrevistados não souberam identificar a nicotina como causadora da dependência, 20,8% não consideravam o tabagismo como doença, e 47,2% responderam não terem recebido nenhum treinamento sobre o tabagismo. Os alunos de medicina da universidade pública mostraram maior conhecimento sobre as diversas formas de tratamento do tabagismo. CONCLUSÕES: A prevalência do tabagismo entre os universitários estudados foi alta. O conhecimento sobre tabagismo foi deficitário, o que poderia refletir uma inadequação da grade curricular dos cursos dessas universidades

Smoking cessation: an integral part of lung cancer treatment

Lung cancer is the leading cause of cancer death in the US. About 50% of lung cancer patients are current smokers at the time of diagnosis and up to 83% continue to smoke after diagnosis. A recent study suggests that people who continue to smoke after a diagnosis of early-stage lung cancer almost double their risk of dying. Despite a growing body of evidence that continued smoking by patients after a lung cancer diagnosis is linked with less effective treatment and a poorer prognosis, the belief prevails that treating tobacco dependence is useless. With improved cancer treatments and survival rates, smoking cessation among lung cancer patients has become increasingly important. There is a pressing need to clarify the role of smoking cessation in the care of lung cancer patients.

OBJECTIVE

This paper will report on the benefits of smoking cessation for lung cancer patients and the elements of smoking cessation treatment, with consideration of tailoring to the needs of lung cancer patients.

RESULTS

Given the significant benefits of smoking cessation and that tobacco dependence remains a challenge for many lung cancer patients, cancer care providers need to offer full support and intensive treatment with a smoking cessation program that is tailored to lung cancer patients' specific needs.

CONCLUSION

A tobacco dependence treatment plan for lung cancer patients is provided.

Strategies for smoking cessation: what is new and what works?

While the prevalence of smoking in the USA has declined over the past half century, there still remain over 40 million current smokers, ensuring that smoking will continue to be a major factor influencing premature morbidity and mortality rates for years to come. Most people begin smoking during their teenage years and struggle to quit as adults. Nicotine dependence should be considered a chronic health condition with exacerbations and remissions. Clinicians have an important role to play in helping their patients to stop smoking. The systematic identification of all smokers is the initial step in addressing smoking cessation. Providing both pharmacotherapy and counseling support for all quit attempts helps to optimize rates of cessation. First-line pharmacotherapy to support a quit attempt include nicotine replacement (gum, patch, lozenge, nasal spray or inhaler), bupropion or varenicline. Use of these agents can increase quit rates by 1.5- to threefold. Several studies have shown that combining the nicotine patch with either gum or nasal spray can increase quit rates over single modality therapy. Recent studies have also suggested that giving smokers stop-smoking medications for several weeks in advance of their quit date may help to boost long-term quit rates. New medications are under development, including a nicotine vaccine and faster delivery nicotine medications. However, from a public health perspective, a ban on the sale of nicotine-containing combustion tobacco products may represent the most straightforward means to minimize the harm caused by tobacco use.

Smoking cessation intervention: an evidence-based approach

Cigarette smoking represents the most important source of preventable morbidity and premature mortality worldwide. Approximately 100 million deaths were caused by tobacco use in the 20th century. There are >1 billion smokers worldwide, and globally the use of tobacco products is increasing, with the epidemic shifting to the developing world. Tobacco dependence is a chronic condition that often requires repeated intervention for success. Just informing a patient about health risks, although necessary, is usually not sufficient for a decision to change. Smokers should be provided with counseling when attempting to quit. Pharmacologic smoking cessation aids are recommended for all smokers who are trying to quit, unless contraindicated. Evidence-based guidelines recommend nicotine replacement therapy, bupropion SR, and varenicline as effective alternatives for smoking cessation therapy, especially when combined with behavioral interventions. Combination pharmacotherapy is indicated for highly nicotine-dependent smokers, patients who have failed with monotherapy, and patients with breakthrough cravings. An additional form of nicotine replacement therapy or an addition of a non-nicotine replacement therapy oral medication (bupropion or varenicline) may be helpful. The rate of successful smoking cessation at 1 year is 3% to 5% when the patient simply tries to stop, 7% to 16% if the smoker undergoes behavioral intervention, and up to 24% when receiving pharmacological treatment and behavioral support.

The nicotinic acetylcholine receptor partial agonist varenicline and the treatment of drug dependence: a review

Drug dependence is a chronic brain disease characterized by recurrent episodes of relapse, even when the person is motivated to quit. Relapse is a major problem and new pharmacotherapies are needed to prevent relapse episodes. The nicotinic acetylcholine receptor (nAChR) plays an important role in nicotine dependence, alcohol consumption and cue-induced cocaine craving. Stimulation of the nAChR has been found to alter and modulate cell firing in brain areas important for the maintenance of drug dependence. Varenicline, an alpha4beta2 nAChR partial agonist and an alpha7 nAChR full agonist registered for the treatment of nicotine dependence, significantly reduces nicotine craving and prevents relapse. In addition, varenicline reduces alcohol consumption in rats. Based on a review of the available literature, we hypothesize a potential role for varenicline in the prevention of relapse in patients recovering from drug dependence other than nicotine dependence.

The multiple facets of cigarette addiction and what they mean for encouraging and helping smokers to stop

Addiction involves powerful motivation to engage in an activity repeatedly to an extent that is harmful often accompanied by impaired capacity for self-control. To effectively combat addiction to cigarettes requires an understanding that there are several mechanisms underlying it. The PRIME Theory of motivation aims to provide a model that can encapsulate these mechanisms. It recognises that evolution has led to multiple levels of motivation from basic impulses and inhibitions, through 'motives' (feelings of want and need), to 'evaluations' (beliefs about what is good or bad), and plans (intentions regarding future actions). Self-control involves self-consciously generating motives from evaluations or plans; it requires and depletes mental energy. Nicotine from cigarettes generates the motivation to smoke and undermines self-control by interacting with all of the level of motivation. It: creates stimulus-impulse associations resulting in cue-driven urges; impairs inhibitory control; gives enjoyment resulting in 'wanting' to smoke; it leads to 'nicotine hunger', withdrawal symptoms and beliefs about benefits of smoking (e.g. stress relief) all of which can result in a 'need' to smoke. Evidence is emerging that wanting to smoke (because of enjoyment) is a major deterrent to making quit attempts but does not influence success, while cue-driven impulses to smoke, nicotine hunger and adverse mood and beliefs about the benefits of smoking are important in relapse. Combating cigarette addiction requires attention to all of these factors.

Current approaches to pharmacotherapy for smoking cessation

It is well established that smoking is the primary preventable cause of disease and death in the United States and that it is responsible for a wide range of negative health consequences, including but not limited to respiratory disease. According to the US Public Health Service, all patients attempting to quit smoking should be encouraged to use one or more effective pharmacotherapy agents for cessation except in the presence of special circumstances or in populations for which there is insufficient evidence of effectiveness (pregnant women, smokeless tobacco users, light smokers and adolescents). These medications are most effective when coupled with behavioral counseling interventions. This review article provides an overview of comprehensive (the 5 A's framework: Ask, Advise, Assess, Assist, Arrange) and brief (Ask, Advise, Refer) interventions for assisting patients with quitting, and a more detailed review of the seven first-line pharmacological agents for smoking cessation (nicotine replacement therapy formulations, bupropion SR and varenicline) and combination therapy regimens. This information will facilitate respiratory therapists in addressing the most important risk factor for pulmonary disease in the patient population that they serve.

Cigarette-by-cigarette satisfaction during ad libitum smoking

Smoking is thought to produce immediate reinforcement, and subjective satisfaction with smoking is thought to influence subsequent smoking. The authors used ecological momentary assessment (A. A. Stone & S. Shiffman, 1994) to assess cigarette-by-cigarette smoking satisfaction in 394 heavy smokers who subsequently attempted to quit. Across 14,882 cigarettes rated, satisfaction averaged 7.06 (0-10 scale), but with considerable variation across cigarettes and individuals. Women and African American smokers reported higher satisfaction. More satisfied smokers were more likely to lapse after quitting (HR = 1.1, p < .03), whereas less satisfied smokers derived greater benefit from patch treatment to help them achieve abstinence (HR = 1.23, p < .001). Cigarettes smoked in positive moods were more satisfying, correcting for mood at the time of rating. The best predictor of subsequent smoking satisfaction was the intensity of craving prior to smoking. Understanding subjective smoking satisfaction provides insight into sources of reinforcement for smoking.

Is nicotine a key player or spectator in the induction and progression of cardiovascular disorders?

Cigarette smoking is common in societies worldwide and a growing body of evidence suggests that chronic cigarette smoking may affect the structure and function of cardiovascular system. The chronic exposure to high levels of nicotine, a major component of cigarette smoking, has been observed to play a pathogenic role in the induction and progression of cardiovascular disorders including cardiomyopathy and peripheral vascular disease. Nicotine alters the function of vascular endothelium, initiates the adhesion cascade and stimulates the vascular inflammatory events to induce atherosclerosis and hypertension. Moreover, nicotine has been noted to induce direct coronary spasm and ischemia, which develop coronary artery disease and myocardial infarction. In addition, nicotine stimulates the excessive release of impulses from sinoatrial node that may account for the induction of cardiac arrhythmia. The present review critically discussed the possible detrimental role of chronic nicotine exposure in cardiac and vascular endothelial dysfunction. Moreover, the signaling mechanisms involved in the pathogenesis of nicotine exposure-induced cardiovascular dysfunction have been discussed. In addition, the pharmacological interventions to ameliorate chronic nicotine exposure-induced cardiovascular abnormalities have been delineated.

A longer course of varenicline therapy improves smoking cessation rates

Smoking exerts strong dose-dependent increases in cardiovascular risk and mortality, and quitting can profoundly decrease these risks. Varenicline attenuates nicotine addiction by reducing withdrawal symptoms and cravings. A meta-analysis performed addressed whether a longer duration of varenicline is associated with better abstinence rates than shorter courses of treatment. For this meta-analysis, a literature search was performed to identify randomized controlled trials investigating the efficacy of the smoking cessation agent varenicline. The association between abstinence and duration of treatment was analyzed using fixed-effect meta-regression. Five randomized controlled trials were identified and included in this meta-analysis. A highly significant relationship (P<.001) was found between the length of exposure to varenicline and abstinence rate. Cessation rates were approximately twice as high with varenicline treatment of 24 weeks compared to 6 weeks. In conclusion, a meta-analysis of randomized controlled trials suggests that longer duration of varenicline therapy improves long-term abstinence rates.

Varenicline: a first-line treatment option for smoking cessation

BACKGROUND

Varenicline acts as a partial agonist/antagonist with affinity and selectivity for alpha(4) beta(2) nicotinic acetylcholine receptors. This activity at the nicotine-receptor level may help patients achieve smoking cessation by reducing cravings/withdrawal symptoms and smoking satisfaction.

OBJECTIVE

This article reviews the literature on the pharmacologic properties, therapeutic efficacy, and tolerability of varenicline for smoking cessation.

METHODS

Pertinent controlled clinical trials, meta-analyses, meeting abstracts, case reports, and review articles published in English between 1966 and May 2008 were identified through searches of MEDLINE and OVID using the terms varenicline, smoking, tobacco cessation, and CP 526555.

RESULTS

Eight clinical trials were identified that compared <or=12 weeks of varenicline treatment with placebo and/or bupropion sustained release (SR); one of the trials reported follow-up data to 24 weeks, and the remainder reported data to 52 weeks. During treatment with oral varenicline titrated to 1 mg BID, CO-confirmed 4-week continuous quit rates/continuous abstinence rates (CQRs/CARs) in weeks 9 through 12 ranged from 43.9% (odds ratio [OR] = 3.85 [95% CI, 2.69-5.50; P < 0.001 vs placebo]; OR = 1.90 [95% CI, 1.38-2.62; P < 0.001 vs bupropion SR]) to 65.4% (OR = 2.98 [95% CI, 1.78-4.99; P < 0.001 vs placebo]). In 4 of these trials, varenicline 1 mg BID was associated with significantly higher CQRs/CARs compared with placebo at week-52 follow-up, ranging from 21.9% (P < 0.001) to 34.6% (P = 0.036). One trial reported a significantly higher CAR at 52 weeks with varenicline compared with bupropion SR (23.0% vs 14.6%, respectively; P = 0.004), and another reported a significantly higher CAR at 52 weeks with varenicline compared with nicotine replacement therapy (25.9% vs 19.8%, respectively; P = 0.040). In a relapse-prevention study that included a 12-week extension period for participants who were abstinent after the initial 12 weeks of treatment, CARs were significantly improved at 24 weeks with varenicline relative to placebo (70.5% vs 49.6%, respectively; OR = 2.48; 95% CI, 1.95-3.16; P < 0.001). Treatment with varenicline was generally well tolerated in study populations with no major comorbidities. In a pooled analysis of 2 Phase III trials, the most commonly reported adverse events (AEs) with varenicline, bupropion SR, and placebo were nausea (28.8%, 9.9%, and 9.1%, respectively), insomnia (14.2%, 21.5%, and 12.6%), and headache (14.2%, 11.1%, and 12.4%). In a pooled analysis of 2 identically designed Phase III trials, bupropion SR was associated with the highest overall rates of discontinuation due to all-cause AEs compared with varenicline and placebo (13.9%, 9.5%, and 8.2%, respectively) and due to AEs considered related to study drug (12.1%, 7.9%, and 6.4%). In double-blind clinical trials of varenicline, nausea was the most frequently reported AE (16.3%-41.9%). Varenicline treatment should begin 7 days before the proposed smoking quit date; dose titration is recommended to minimize dose-related nausea. Based on postmarketing reports of serious AEs in vareniclinetreated patients, caution is recommended when operating vehicles or heavy machinery. Patient education and monitoring for potential AEs are also recommended, particularly in patients with a history of psychiatric illness.

CONCLUSIONS

Varenicline has a unique mechanism of action compared with other first-line options for smoking cessation. Available clinical-trial data support its use as an effective and generally well-tolerated therapy for smoking cessation in healthy adult smokers, although there is a need for further efficacy and safety evaluation in the general population, particularly those with comorbid conditions.

Mechanism-based medication development for the treatment of nicotine dependence

Tobacco use is a global problem with serious health consequences. Though some treatment options exist, there remains a great need for new effective pharmacotherapies to aid smokers in maintaining long-term abstinence. In the present article, we first discuss the neural mechanisms underlying nicotine reward, and then review various mechanism-based pharmacological agents for the treatment of nicotine dependence. An oversimplified hypothesis of addiction to tobacco is that nicotine is the major addictive component of tobacco. Nicotine binds to alpha4beta2 and alpha7 nicotinic acetylcholine receptors (nAChRs) located on dopaminergic, glutamatergic and GABAergic neurons in the mesolimbic dopamine (DA) system, which causes an increase in extracellular DA in the nucleus accumbens (NAc). That increase in DA reinforces tobacco use, particularly during the acquisition phase. Enhanced glutamate transmission to DA neurons in the ventral tegmental area appears to play an important role in this process. In addition, chronic nicotine treatment increases endocannabinoid levels in the mesolimbic DA system, which indirectly modulates NAc DA release and nicotine reward. Accordingly, pharmacological agents that target brain acetylcholine, DA, glutamate, GABA, or endocannabonoid signaling systems have been proposed to interrupt nicotine action. Furthermore, pharmacokinetic strategies that alter plasma nicotine availability, metabolism and clearance also significantly alter nicotine's action in the brain. Progress using these pharmacodynamic and pharmacokinetic agents is reviewed. For drugs in each category, we discuss the mechanistic rationale for their potential anti-nicotine efficacy, major findings in preclinical and clinical studies, and future research directions.

Visual hallucinations associated with varenicline: a case report

Introduction

Varenicline is widely used for smoking cessation. It has shown efficacy over placebo and bupropion in manufacturer-sponsored trials. Those with mental illness were excluded from these trials. There are case reports of exacerbation of mental illness and development of psychiatric symptoms with varenicline use.

Case presentation

A 61-year-old male Caucasian being treated for post-traumatic stress disorder, depression not otherwise specified and alcohol dependence, was prescribed varenicline while he was in a post-traumatic stress disorder/alcohol dual diagnosis treatment program. He developed visual hallucinations, which became worse with titration of the medication. These symptoms resolved upon discontinuation of varenicline.

Conclusion

Patients with mental illness have a higher incidence of nicotine dependence, and attempts should be made for smoking cessation. Varenicline has not been widely tested in this population. There are reports of exacerbation of mental illness, and probable causation of psychiatric symptoms in the mentally ill. Providers should be aware of this possibility and advise their patients appropriately.