Cytisine for smoking cessation: A systematic review and meta-analysis

Abstract

Background: Cytisine is a smoking cessation medication. This systematic review incorporates recently published randomized controlled trials (RCTs) to provide an updated evidence-based assessment of cytisine's efficacy and safety.

Methods: We searched Cochrane Library, MEDLINE, and EMBASE, for RCTs comparing cytisine to other smoking cessation treatments in adults who smoke.

Primary outcome: 6-month biochemically verified continuous abstinence. Other outcomes: abstinence at longest follow-up, adverse events, mortality, and health-related quality of life (HRQOL). We used Grading of Recommendations Assessment, Development and Evaluation (GRADE) to assess evidence certainty.

Results: We included 14 RCTs involving 9953 adults. Cytisine was superior to placebo (risk ratio [RR] 2.25, 95% confidence interval [CI] 1.13-4.47; 5 RCTs, 4325 participants), but not varenicline (RR 1.13, 95% CI 0.65-1.95; 2 RCTs, 2131 participants) for the primary outcome. Cytisine was superior to placebo (RR 2.78, 95% CI 1.64-4.70; 8 RCTs, 5762 participants) and nicotine replacement therapy [NRT] (RR 1.39, 95% CI 1.12-1.73; 2 RCTs, 1511 participants), but not varenicline (RR 1.02, 95% CI 0.72-1.44; 4 RCTs, 2708 participants) for abstinence at longest follow-up. Cytisine increased mostly gastrointestinal adverse events compared to placebo (RR 1.15; 95% CI 1.06-1.25; 8 RCTs, 5520 participants) and NRT (RR 1.52, 95% CI 1.26-1.84; 1 RCT, 1310 participants) but less adverse events compared to varenicline (RR 0.67; 95% CI 0.48-0.95; 3 RCTs, 2484 participants).

Conclusion: Cytisine shows greater efficacy than placebo and NRT, but more adverse events. It is comparable to varenicline, with fewer adverse events. This can inform clinicians and guidelines on cytisine for smoking cessation.

Keywords: Cytisine; Nicotine replacement; Placebo; Smoking cessation; Varenicline.