Harms associated with taking nalmefene for substance use and impulse control disorders: A systematic review and meta-analysis of randomised controlled trials

Importance Nalmefene is a newly approved drug for alcohol use disorder, but the risk of harms has not been evaluated from empirical trial evidence. Objective To assess the harm of nalmefene administered to individuals diagnosed with substance use or impulse control disorders by performing a systematic review and meta-analysis of randomised controlled trials. Data sources A search was performed in Cochrane Central Register of Controlled Trials (CENTRAL, 2014), MEDLINE via PubMed (1950), EMBASE via Ovid (1974), and Clinicaltrials. gov through December 2014. Study selection This study included only randomised controlled trials with placebo or active controls that administered nalmefene to adult individuals for treating impulse control and/or substance use disorders. Both published and unpublished randomised controlled trials were eligible for inclusion. Data extraction and synthesis Internal validity was assessed using the Cochrane risk-of-bias tool. Published information from the trials was supplemented by contact between reviewers and industry sponsor. Data were combined using two meta-approaches in fixed effects models; Peto Odds Ratios and risk differences were reported with 95% confidence intervals (95% CIs). Main outcomes and measures Number of patients with serious adverse events, including specific psychiatric serious adverse events and withdrawals due to adverse events. Results Of 20 potentially relevant studies, 15 randomised controlled trials met the inclusion criteria, and 8 of these provided data enabling the meta-analysis. Overall, serious adverse events did not occur more often in the nalmefene group than in the placebo group (Peto Odds Ratio = 0.97 [95% CI 0.64 - 1.44]; P = 0.86). Risk of psychiatric serious adverse events was slightly elevated, albeit not at a statistically significant level (Peto Odds Ratio = 1.32 [95% CI 0.62, 2.83]; P = 0.47). Withdrawals due to adverse events were significantly more likely to occur with nalmefene compared to placebo (Peto Odds Ratio = 3.22 [95% CI 2.46 - 4.22]; P<0.001) Conclusions and relevance The three-fold increased risk of withdrawal from treatment on nalmefene due to adverse events is a matter of safety concern. The nature of these adverse events cannot be elucidated further without access to individual patients data.