Objective: An overview, meta-analysis, and trial sequential analysis were conducted to evaluate the efficacy and safety of varenicline for smoking cessation. Methods: Systematic reviews (SRs) and randomized controlled trials evaluating varenicline versus placebo for smoking cessation were included. A forest plot was used to summarize the effect size of the included SRs. Traditional meta-analysis and trial sequential analysis (TSA) were performed using Stata software and TSA 0.9 software, respectively. Finally, the Grades of Recommendation, Assessment, Development, and Evaluation approach was used to assess the quality of evidence for the abstinence effect. Results: A total of 13 SRs and 46 randomized controlled trials were included. Twelve review studies showed that varenicline was superior to placebo for smoking cessation. The meta-analysis results showed that, compared with the placebo, varenicline significantly increased the odds of smoking cessation (odds ratio = 2.54, 95% confidence interval = 2.20-2.94, P < 0.05, moderate quality). Subgroup analysis showed that there were significant differences in smokers with disease and general smokers (P < 0.05). Differences were also found in the follow-up time at 12, 24, and 52 weeks (P < 0.05). The common adverse events were nausea, vomit, abnormal dreams, sleep disturbances, headache, depression, irritability, indigestion, and nasopharyngitis (P < 0.05). The TSA results confirmed the evidence for the effect of varenicline on smoking cessation. Conclusions: Existing evidence supports the superiority of varenicline over a placebo for smoking cessation. Varenicline had mild to moderate adverse events but was well tolerated. Future trials should investigate varenicline in combination with other smoking cessation approaches and compare it with other interventions.

Objective: A network meta-analysis based on randomized controlled trials was conducted to investigate the effects of pharmacological interventions on smoking cessation. Methods: English databases were searched to obtain randomized controlled trials reporting the effect of pharmacological interventions on smoking cessation. The risk of bias for the included trials was assessed using Cochrane Handbook tool. Stata 15.1 software was used to perform network meta-analysis, and GRADE approach was used to assess the evidence credibility on the effects of different interventions on smoking cessation. Results: A total of 159 studies involving 60,285 smokers were included in the network meta-analysis. The analysis involved 15 interventions and which yielded 105 pairs of comparisons. Network meta-analysis showed that varenicline was more helpful for smoking cessation than other monotherapies, such as nicotine replacement therapy [Odds Ratio (OR) = 1.42, 95% confidence interval (CI) (1.16, 1.73)] and bupropion [OR = 1.52, 95% CI (1.22, 1.89)]. Furthermore, combined interventions were superior to monotherapy in achieving smoking cessation, such as varenicline plus bupropion over bupropion [OR = 2.00, 95% CI (1.11, 3.61)], varenicline plus nicotine replacement therapy over nicotine replacement therapy [OR = 1.84, 95% CI (1.07, 3.18)], and nicotine replacement therapy plus mecamylamine over naltrexone [OR = 6.29, 95% CI (1.59, 24.90)]. Finally, the surface under the cumulative ranking curve value indicated that nicotine replacement therapy plus mecamylamine had the greatest probability of becoming the best intervention. Conclusion: Most pharmacological interventions demonstrated a benefit in smoking cessation compared with placebo, whether monotherapy or combination therapy. Moreover, confirmed evidence suggested that some combination treatments, such as varenicline plus bupropion and nicotine replacement therapy plus mecamylamine have a higher probability of being the best smoking cessation in