Risk of serious adverse cardiovascular events associated with varenicline: a systematic review and meta-analysis

Tobacco addiction and the dysregulation of brain stress systems

Tobacco is a highly addictive drug and is one of the most widely abused drugs in the world. The first part of this review explores the role of stressors and stress-associated psychiatric disorders in the initiation of smoking, the maintenance of smoking, and relapse after a period of abstinence. The reviewed studies indicate that stressors facilitate the initiation of smoking, decrease the motivation to quit, and increase the risk for relapse. Furthermore, people with depression or an anxiety disorder are more likely to smoke than people without these disorders. The second part of this review describes animal studies that investigated the role of brain stress systems in nicotine addiction. These studies indicate that corticotropin-releasing factor, Neuropeptide Y, the hypocretins, and norepinephrine play a pivotal role in nicotine addiction. In conclusion, the reviewed studies indicate that smoking briefly decreases subjective stress levels but also leads to a further dysregulation of brain stress systems. Drugs that decrease the activity of brain stress systems may diminish nicotine withdrawal and improve smoking cessation rates.

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

The primary objective of this review is to assess the efficacy and tolerability of nicotine receptor partial agonists, including cytisine, dianicline and varenicline 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, PsycINFO and Web of Science 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 December 2011. We also searched online clinical trials registers.

SELECTION CRITERIA

We included randomized 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 randomization 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 recent cytisine trials (937 people) found that more participants taking cytisine stopped smoking compared with placebo at longest follow-up, with a pooled RR of 3.98 (95% confidence interval (CI) 2.01 to 7.87). One trial of dianicline (602 people) failed to find evidence that it was effective (RR 1.20, 95% CI 0.82 to 1.75). Fifteen trials compared varenicline with placebo for smoking cessation; three of these also included a bupropion treatment arm. We also found one open-label trial comparing varenicline plus counselling with counselling alone. We found one relapse prevention trial, comparing varenicline with placebo, and two open-label trials comparing varenicline with nicotine replacement therapy (NRT). We also include one trial in which all the participants were given varenicline, but received behavioural support either online or by phone calls, or by both methods. This trial is not included in the analyses, but contributes to the data on safety and tolerability. The included studies covered 12,223 participants, 8100 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 2.27 (95% CI 2.02 to 2.55; 14 trials, 6166 people, excluding one trial evaluating long term safety). Varenicline at lower or variable doses was also shown to be effective, with an RR of 2.09 (95% CI 1.56 to 2.78; 4 trials, 1272 people). The pooled RR for varenicline versus bupropion at one year was 1.52 (95% CI 1.22 to 1.88; 3 trials, 1622 people). The RR for varenicline versus NRT for point prevalence abstinence at 24 weeks was 1.13 (95% CI 0.94 to 1.35; 2 trials, 778 people). The two 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 main adverse effect of varenicline was nausea, which was mostly at mild to moderate levels and usually subsided over time. A meta-analysis of reported serious adverse events occurring during or after active treatment and not necessarily considered attributable to treatment suggests there may be a one-third increase in the chance of severe adverse effects among people using varenicline (RR 1.36; 95% CI 1.04 to 1.79; 17 trials, 7725 people), but this finding needs to be tested further. Post-marketing safety data have raised questions about a possible association between varenicline and depressed mood, agitation, and suicidal behaviour or ideation. The labelling of varenicline was amended in 2008, and the manufacturers produced a Medication Guide. Thus far, surveillance reports and secondary analyses of trial data are inconclusive, but the possibility of a link between varenicline and serious psychiatric or cardiovascular events cannot be ruled out.

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 threefold 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. Two open-label trials of varenicline versus NRT suggested a modest benefit of varenicline but confidence intervals did not rule out equivalence. Limited evidence suggests that varenicline may have a role to play in relapse prevention. The main adverse effect of varenicline is nausea, but mostly at mild to moderate levels and tending to subside over time. Possible links with serious adverse events, including serious psychiatric or cardiovascular events, cannot be ruled out.Future trials of cytisine may test extended regimens and more intensive behavioural support. There is a need for further trials of the efficacy of varenicline treatment extended beyond 12 weeks.

Preclinical evidence that activation of mesolimbic alpha 6 subunit containing nicotinic acetylcholine receptors supports nicotine addiction phenotype

INTRODUCTION

Nicotine is a major psychoactive ingredient in tobacco yet very few individuals quit smoking with the aid of nicotine replacement therapy. Targeted therapies with more selective action at nicotinic acetylcholine receptors (nAChRs) that contain a β2 subunit (β2*nAChRs; *denotes assembly with other subunits) have enjoyed significantly greater success, but exhibit potential for unwanted cardiac, gastrointestinal, and emotive side effects.

DISCUSSION

This literature review focuses on the preclinical evidence that suggests that subclasses of β2*nAChRs that assemble with the α6 subunit may provide an effective target for tobacco cessation. α6β2*nAChRs have a highly selective pattern of neuroanatomical expression in catecholaminergic nuclei including the ventral tegmental area and its projection regions. α6β2*nAChRs promote dopamine (DA) neuron activity and DA release in the mesolimbic dopamine system, a brain circuitry that is well-studied for its contributions to addiction behavior. A combination of genetic and pharmacological studies indicates that activation of α6β2*nAChRs is necessary and sufficient for nicotine psychostimulant effects and nicotine self-administration. α6β2*nAChRs support maintenance of nicotine use, support the conditioned reinforcing effects of drug-associated cues, and regulate nicotine withdrawal.

CONCLUSIONS

These data suggest that α6β2*nAChRs represent a critical pool of high affinity β2*nAChRs that regulates nicotine dependence phenotype and suggest that inhibition of these receptors may provide an effective strategy for tobacco cessation therapy.

Preventive aspects in peripheral artery disease

The prevalence of peripheral artery disease is steadily increasing and is associated with significant morbidity, including a significant percentage of amputations. Peripheral artery disease often goes undiagnosed, making its prevention increasingly important. Patients with peripheral arterial disease are at increased risk of adverse cardiovascular outcomes which makes prevention even more important. Several risk factors have been identified in the pathophysiology of peripheral artery disease which should be modified to decrease risk. Smoking, hyperlipidemia, hypertension, and diabetes are among proven risk factors for the development of peripheral artery disease, thus smoking cessation, lipid control, blood pressure control, and glucose control have been tried and shown to be effective in preventing the morbidity associated with this disease. Pharmacologic agents such as aspirin and clopidogrel alone or in combination have been shown to be effective, though risk of bleeding might be increased with the combination. Anticoagulation use is recommended only for acute embolic cases. Other treatment modalities that have been tried or are under investigation are estrogen replacement, naftidrofuryl, pentoxifylline, hyperbaric oxygen, therapeutic angiogenesis, and advanced glycation inhibitors. The treatment for concomitant vascular diseases does not change in the presence of peripheral artery disease, but aggressive management of risk factors should be undertaken in such cases.

PURLs: Counseling is a must with this smoking cessation aid

For many smokers, the benefits of quitting will outweigh the risks associated with varenicline.

Systematic review of the cost-effectiveness of varenicline vs. bupropion for smoking cessation

The purpose of this systematic review was to review the cost-effectiveness of first-line non-nicotine therapies (varenicline and bupropion SR) for smoking cessation, identify differences in the models used and their conclusions of cost-effectiveness, and to determine which variables, if any, impact conclusions of cost-effectiveness. A systematic literature search was conducted in MEDLINE, PsychINFO, the National Health Service Economic Evaluation Database, the Health Technology Database and the Tufts Cost-effectiveness Analysis Registry from the earliest possible date through May 2011. To be included, studies had to compare cost-effectiveness of varenicline to bupropion using either a Markov model or discrete event simulation and be published as a full text manuscript in English or Spanish. Study selection and data extraction were done in duplicate with disagreement resolved through discussion. Data regarding the model characteristics, results and conclusions were extracted as were details to assess the quality of the study. Model characteristics and cost-effectiveness results were compared across studies and summarised qualitatively. Ten unique studies were included, all of which were Markov models. Eight studies used the Benefits of Smoking Cessation on Outcomes (BENESCO) model and all found varenicline to dominate bupropion. The two non-BENESCO models found varenicline to be cost-effective. Conclusions regarding the cost-effectives were changed upon sensitivity analysis with the following variables: time horizon, cost of bupropion, efficacy of either drug, age and the incidence of smoking related disease. Varenicline dominated bupropion in most cost-effectiveness models. However, applicability of models to clinical practice and variables which changed conclusion of cost-effectiveness should be considered in the interpretation of results.

Safety and tolerability of varenicline tartrate (Champix(®)/Chantix(®)) for smoking cessation in HIV-infected subjects: a pilot open-label study

The prevalence of smoking in HIV-infected subjects is high. As a smoking cessation aid, varenicline (Champix(®), Pfizer, Saint-Laurent, QC, Canada or Chantix(®), Pfizer, Mission, KS) has not been previously evaluated in HIV-infected smokers. In this multicenter pilot open label study, varenicline 1.0 mg was used twice daily for 12 weeks with dose titration in the first week. Adverse events (AEs) during the treatment period were recorded. Changes from baseline in laboratory tests, vital signs, daily cigarette consumption, nicotine dependence, and withdrawal were measured through week 24. Self-reported abstinence was validated by serum cotinine at week 12. We enrolled 36 subjects with a mean of 29 pack-years of smoking and a minimum of 4 cigarettes per day. All but 1 were male, 33 (92%) were white. The most frequently reported AEs were nausea (33%), abnormal dreams (31%), affect lability (19%), and insomnia (19%). Six (17%) subjects discontinued varenicline due to AEs. No grade 3/4 laboratory abnormalities or serious AEs occurred during the study. There was no significant change in HIV viral load. CD4 counts increased by 69 cells/mm3 (p = 0.001) at week 24. Serum cotinine-verified 4-week continuous abstinence rate through weeks 9-12 was 42% (95% confidence interval [CI]: 26-58%). AEs and abstinence rates were comparable to those in published randomized controlled trials conducted in generally healthy HIV-negative smokers. Varenicline was safe and appears effective among HIV-infected smokers in this exploratory study, although AEs were common. The most common AE was nausea, with no adverse effect on HIV treatment outcome. Close monitoring of liver enzymes and blood pressure is recommended for HIV-positive smokers taking varenicline.

[Risk factor "smoking" : smoking cessation in patients with cardiovascular diseases]

Smoking is the most frequent cause of avoidable premature death. Annually, almost 6 million people die due to nicotine consumption. Comparing modifiable cardiovascular risk factors, smoking has the strongest impact on cardiovascular mortality. More than 50% of all premature myocardial infarctions are related to nicotine consumption. Even in patients with known coronary disease receiving optimal medical therapy, there is a remarkable additional preventive effect of smoking cessation detectable. Therefore, smoking cessation is an essential component of primary and secondary prevention strategies. Smoking cessation programs applying a combination of behavior therapy and supporting medical treatment have been demonstrated to be the most effective.

3D-QSAR and 3D-QSSR models of negative allosteric modulators facilitate the design of a novel selective antagonist of human α4β2 neuronal nicotinic acetylcholine receptors

Subtype selective molecules for α4β2 neuronal nicotinic acetylcholine receptors (nAChRs) have been sought as novel therapeutics for nicotine cessation. α4β2 nAChRs have been shown to be involved in mediating the addictive properties of nicotine while other subtypes (i.e., α3β4 and α7) are believed to mediate the undesired effects of potential CNS drugs. To obtain selective molecules, it is important to understand the physiochemical features of ligands that affect selectivity and potency on nAChR subtypes. Here we present novel QSAR/QSSR models for negative allosteric modulators of human α4β2 nAChRs and human α3β4 nAChRs. These models support previous homology model and site-directed mutagenesis studies that suggest a novel mechanism of antagonism. Additionally, information from the models presented in this work was used to synthesize novel molecules; which subsequently led to the discovery of a new selective antagonist of human α4β2 nAChRs.

Suicidal behavior and depression in smoking cessation treatments

BACKGROUND

Two treatments for smoking cessation--varenicline and bupropion--carry Boxed Warnings from the U.S. Food and Drug Administration (FDA) about suicidal/self-injurious behavior and depression. However, some epidemiological studies report an increased risk in smoking or smoking cessation independent of treatment, and differences between drugs are unknown.

METHODOLOGY

From the FDA's Adverse Event Reporting System (AERS) database from 1998 through September 2010 we selected domestic, serious case reports for varenicline (n = 9,575), bupropion for smoking cessation (n = 1,751), and nicotine replacement products (n = 1,917). A composite endpoint of suicidal/self-injurious behavior or depression was defined as a case with one or more Preferred Terms in Standardized MedDRA Query (SMQ) for those adverse effects. The main outcome measure was the ratio of reported suicide/self-injury or depression cases for each drug compared to all other serious events for that drug.

RESULTS

Overall we identified 3,249 reported cases of suicidal/self-injurious behavior or depression, 2,925 (90%) for varenicline, 229 (7%) for bupropion, and 95 (3%) for nicotine replacement. Compared to nicotine replacement, the disproportionality results (OR (95% CI)) were varenicline 8.4 (6.8-10.4), and bupropion 2.9 (2.3-3.7). The disproportionality persisted after excluding reports indicating concomitant therapy with any of 58 drugs with suicidal behavior warnings or precautions in the prescribing information. An additional antibiotic comparison group showed that adverse event reports of suicidal/self-injurious behavior or depression were otherwise rare in a healthy population receiving short-term drug treatment.

CONCLUSIONS

Varenicline shows a substantial, statistically significant increased risk of reported depression and suicidal/self-injurious behavior. Bupropion for smoking cessation had smaller increased risks. The findings for varenicline, combined with other problems with its safety profile, render it unsuitable for first-line use in smoking cessation.

Transdermal Nicotine Replacement Therapy Safety in Patients with Cardiovascular Disease

Purpose

The safety and efficacy of nicotine replacement therapy in patients with stable cardiovascular disease and following an acute coronary event are reviewed.

Summary

Physicians have been hesitant to prescribe nicotine replacement therapy (NRT) in patients with cardiac disease due to the reported harmful cardiovascular effects of nicotine, including an increase in heart rate and blood pressure, as well as its possible contribution to the pathogenesis of coronary artery disease and sudden cardiac death. However, several studies have shown that NRT is safe following myocardial infarction and is preferred over continued cigarette smoking. One cohort study assessed the safety and efficacy of transdermal NRT in smokers admitted for acute coronary syndromes and found no difference in mortality versus patients given a placebo. Additionally, the cost of NRT should not be viewed as a barrier due to the long-term savings in preventable hospitalizations following additional cardiovascular events.

Conclusion

Transdermal NRT was found to be safe and effective in patients with acute myocardial infarction and with a known history of cardiovascular disease. It has also proven to be effective in smoking cessation, which eliminates the most important risk factor for an acute coronary event. NRT showed no increased frequency in mortality or other cardiac adverse events.

The Relationship between Smoking and Depression Post-Acute Coronary Syndrome

The purpose of the current paper is to review research on the relationship between smoking cessation and depressed mood post-Acute Coronary Syndrome (Myocardial infarction or unstable angina; ACS). Emerging evidence regarding the effect of anhedonia-a specific subcomponent of mood disturbance characterized by reduced pleasure-on post-ACS outcomes is also discussed. There is strong evidence that depression prospectively predicts post-ACS relapse to smoking. Weaker evidence suggests that smoking at the time of ACS is related to post-ACS depression. Bupropion is a particularly promising treatment for this population because of its smoking cessation and anti-depressant effects. Future research should focus on the relative risk of using nicotine replacement therapies post-ACS, the efficacy of bupropion for smoking cessation and depression reduction in post-ACS patients, the role of anhedonia in post-ACS smoking cessation, and the development and testing of integrated behavioral treatments (smoking cessation plus interventions targeting mood management) for ACS patients.

Treatment of tobacco dependence

BACKGROUND

110 000 to 140 000 people die in Germany each year of tobacco-related diseases. Thus, measures should be taken to lower the number of persons who start smoking, encourage smokers to stop, and keep those who have stopped from starting again, in order to achieve a sustained benefit in public health.

METHOD

We present recommendations for the diagnostic evaluation, counseling, psychotherapy, and pharmacotherapy of smokers, derived from the findings of current Cochrane meta-analyses and from the pertinent German-language and American guidelines.

RESULTS

Motivational interviewing by a physician, including a recommendation to stop smoking and counseling on how to do this, can reinforce a smoker's motivation to quit. Behavioral therapeutic approaches support changes in behavior, while medical aids such as nicotine replacement therapy, bupropion, and varenicline help former smokers overcome the initial withdrawal symptoms. Low-threshold measures such as self-help books, telephone counseling, and Internet-based cessation programs complement the evidence-based treatments. With a combination of medications and psychotherapeutic support, abstinence rates of up to approximately 40% can be achieved at the end of one year.

CONCLUSION

Smokers who decide to quit can benefit from their doctors' support. Physicians should be taught about tobacco dependency and how to treat it as part of their undergraduate medical education, residency training, and continuing medical education.