Varenicline: quantifying the risk

Low incidence of adverse events following varenicline initiation among opioid dependent smokers with comorbid psychiatric illness

BACKGROUND

Most drug treatment patients smoke cigarettes, yet few data exist on the prevalence and outcomes of varenicline treatment among smokers with comorbid substance use and psychiatric disorders.

METHODS

We reviewed all patient charts of opioid-dependent smokers prescribed varenicline between May 2006 and December 2009 in two urban methadone clinics that also provide on-site medical and psychiatric care. We assessed prevalence, adverse events, and effectiveness of varenicline treatment in this cohort.

RESULTS

We identified 575 smokers among 690 patients (83.3%), and assessed 82 courses of varenicline treatment prescribed to 70 smokers. Both cardiovascular risk factors and psychiatric illness were highly prevalent among those prescribed varenicline: hypertension, 51%; hyperlipidemia, 23%; diabetes, 20%; depression, 53%; anxiety, 30%; psychotic disorders, 10%; bipolar disorder, 8.6%. Of 82 varenicline courses, nine (11%) were discontinued due to adverse events and two due to depressive symptoms. One patient initiated new psychiatric medications within six months of initiating varenicline, but did not discontinue varenicline. There were no reports of suicidal ideation, agitation prompting clinical intervention, or psychiatric hospitalization. There were no incident cardiac or vascular events within six months of varenicline prescription. Some (8.6%) varenicline-treated smokers quit smoking, and cessation was significantly associated with varenicline treatment duration.

CONCLUSIONS

Despite substantial comorbidity, opioid-dependent smokers receiving integrated substance abuse, medical and psychiatric care had few documented adverse events with varenicline treatment. Methadone patients will likely experience little harm and a great deal of benefit from treatment with varenicline for smoking cessation.

Use of varenicline for smoking cessation and risk of serious cardiovascular events: nationwide cohort study

OBJECTIVE

To investigate whether varenicline is associated with an increased risk of serious cardiovascular events compared with another drug used for smoking cessation, bupropion.

DESIGN

Nationwide historical cohort study.

SETTING

Denmark, 2007-10.

PARTICIPANTS

New users of varenicline (n = 17,926) and bupropion (n = 17,926).

MAIN OUTCOME MEASURES

Individual level data on dispensed drug prescriptions, cardiovascular events, and potential confounders were linked between registries. Cox regression was used to estimate hazard ratios of cardiovascular events in analyses matched for propensity score. The primary outcomes at six months after start of treatment were acute coronary syndrome, ischaemic stroke, and cardiovascular death analysed individually and as a composite of any major event.

RESULTS

There were 57 major cardiovascular events among varenicline users (6.9 cases per 1000 person years) compared with 60 events among bupropion users (7.1 cases per 1000 person years); the hazard ratio for any major event was 0.96 (95% confidence interval 0.67 to 1.39). Varenicline use was not associated with an increased risk of acute coronary syndrome (1.20, 0.75 to 1.91), ischaemic stroke (0.77, 0.40 to 1.48), and cardiovascular death (0.51, 0.13 to 2.02). In subgroup analyses, the risk of any major cardiovascular event was not significantly different between patients with and without a history of cardiovascular disease (1.24 (0.72 to 2.12) and 0.83 (0.51 to 1.36), respectively; P=0.29).

CONCLUSIONS

This cohort study found no increased risk of major cardiovascular events associated with use of varenicline compared with bupropion for smoking cessation. On the basis of the upper confidence limit, the data allowed the exclusion of a 40% increased risk of the composite outcome of any major cardiovascular event. While the estimates were less precise for specific outcomes, any differences would be small in absolute terms.

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.