A hyperactive endocannabinoid signalling system may contribute to addictions. We tested the efficacy and safety of surinabant, a novel selective CB₁ cannabinoid receptor antagonist, for smoking cessation. In a randomized, double-blind, placebo-controlled, parallel-group clinical trial, participants were assigned to brief counselling and one of three doses of surinabant, 2.5 mg/day (n = 199), 5 mg/day (n = 204), or 10 mg/day (n = 205) or placebo (n = 202) orally for 8 weeks with 6 weeks of non-drug follow-up. For weeks 5 through 8, the 4-week continuous abstinence rates were 25.2% for placebo vs. 22.6%, 22.1% and 21.5% for 2.5 mg/day, 5 mg/day and 10 mg/day doses of surinabant (p for trend, 0.4). The gain in body weight from baseline was reduced with surinabant 2.5 mg/day, 5 mg/day and 10 mg/day (0.75 kg [SE, 0.13], 0.53 kg [SE, 0.13], and 0.24 kg [SE, 0.13], respectively, versus 1.19 kg [SE, 0.13] for placebo; p for trend, < 0.001). The most common adverse events for participants receiving active drug with a greater incidence than placebo were headache, nausea, insomnia, anxiety, nasopharyngitis, diarrhoea and hyperhidrosis. Surinabant did not improve smoking cessation rates compared with placebo, but had a small effect on reducing post-cessation weight gain.
Trial registration: ClinicalTrials.gov NCT00432575.