Slow-release L-cysteine Lozenges in Smoking Cessation: Meta-analysis of Two Randomized Controlled Trials

The hypothesis that elimination of cigarette smoke-derived acetaldehyde in the saliva by slow-release L-cysteine would eliminate acetaldehyde-enhanced nicotine addiction among smokers has been tested in two randomized controlled trials (RCT) using Acetium^® lozenge (Biohit Oyj, Helsinki, Finland). Both RCTs showed a similar direction and magnitude of the effect size, but only the larger study was adequately powered to reach statistical significance.

The two published RCTs on Acetium^® in smoking intervention included in this formal meta-analysis include: a cohort of 423 cigarette smokers, randomly allocated to intervention (n=212) and placebo arms (n =211) in Study 1, as well as a cohort of 1,998 smokers, with 996 and 1,002 subjects in the intervention and placebo arms, respectively, in Study 2. Both studies analyzed the results for intention-to-treat (ITT) and per protocol (PP) compliance groups. Random-effects (RE) meta-analysis was used to compute the summary effect size.

In the ITT group of Study 1, Acetium^® was more effective than placebo, with OR=1.48 (95% CI=0.87-2.54), and in Study 2, the respective OR=1.26 (95% CI=0.99-1.59). In the PP groups, the success rates in both studies were better: OR=1.65 (95% CI=0.75-3.62) and OR=1.51 (95% CI=1.12-2.02), respectively. In RE meta-analysis, the summary estimates of Acetium^® efficacy were statistically significant in both the ITT (n=2,421) and PP (n=863) analysis: OR=1.29 (95% CI=1.04-1.60, p=0.018) and OR=1.53 (95% CI=1.16-2.01, p=0.0025), respectively.

Although meta-analyses with a limited number of studies should be interpreted with caution, these data provide clear support to the concept that Acetium^® lozenge significantly (1.5-fold) increases the likelihood of successful smoking cessation as compared to placebo.