Use of varenicline versus bupropion and risk of psychiatric adverse events

Abstract

Aim: To investigate whether varenicline use was associated with increased risk of psychiatric adverse events, compared with bupropion, another drug used for smoking cessation.

Design, setting and participants: We conducted a registry-based cohort study in Denmark, 2007-10, comparing new users of varenicline and bupropion in unmatched and 1 : 1 propensity score-matched analyses.

Measurements: Using Cox regression, we estimated the hazard ratio (HR) of any psychiatric adverse event (emergency department visit or in-patient admission with a psychiatric diagnosis) within 30 days following treatment initiation. The unmatched and matched analyses correspond to conventional crude and fully adjusted analyses, respectively.

Findings: In unmatched analyses, there were 106 (0.18%) psychiatric adverse events among 59 790 varenicline users (rate 22 events per 1000 person-years), compared with 46 (0.26%) events among 17 936 bupropion users (rate 31 per 1000); the HR was 0.69 [95% confidence interval (CI): 0.49-0.98]. In propensity score-matched analyses, 39 (0.22%) events occurred among 17 935 varenicline users (rate 27 per 1000), compared with 46 (0.26%) events among 17 935 bupropion users (rate 31 per 1000); varenicline was not associated with increased risk of psychiatric adverse events (HR 0.85, 95% CI: 0.55-1.30). The overall rate of psychiatric adverse events was substantially higher among participants with a history of psychiatric disorder than in patients without such history; the risk associated with varenicline did not differ significantly by history of psychiatric disorder.

Conclusions: In Denmark, the risk of psychiatric adverse events diagnosed during an emergency department visit or in-patient admission was not significantly higher with varenicline use compared with bupropion.