The Effects of Pharmacological Interventions on Smoking Cessation in People with Alcohol Dependence: A Systematic Review and Meta-analysis of Nine Randomized Controlled Trials

Background Pharmacotherapies are widely used for smoking cessation. However, their effect on smoking cessation for people with alcohol dependence remains unclear. Objective This study aimed to explore the effects of pharmacotherapies on smoking cessation for people with alcohol dependence. Methods Five electronic databases were searched in January 2021 for randomized controlled trials (RCTs) reporting the use of pharmacotherapies to promote smoking cessation in people with alcohol dependence. The risk of bias was assessed using the Cochrane tool. RevMan version 5.3 was used to perform meta-analyses of the changes in smoking behavior, and the GRADE approach was used to assess the certainty of the evidence. Results Nine RCTs involving 908 smokers with alcohol dependence were identified. Eight RCTs were published in the United States, and one was from Canada. The risk of bias was rated as low in three studies and unclear in the remaining six. The results of the meta-analysis showed that, compared with the placebo group, Varenicline had a significant effect on short-term smoking cessation (three RCTs, OR = 6.27, 95% CI: [2.49, 15.78], p < 0.05, very low certainty). Naltrexone had no significant effect on smoking cessation in short-term or long-term observations (three RCTs, OR = 0.99, 95% CI: [0.54, 1.81], p = 0.97, moderate certainty), and Topiramate had no significant effect (two RCTs, OR = 1.56, 95% CI: [0.67, 3.46], p > 0.05, low certainty). Only one trial reported that Bupropion had no effect on smoking cessation. Conclusion Varenicline may have a positive effect on smoking cessation in people with alcohol dependence. However, Naltrexone, Topiramate, and Bupropion seem to have no clear effect on increasing smoking abstinence among drinkers. The small number of studies and the low certainty of evidence indicate that caution is required in interpreting the results.