Purpose: Nabilone is a synthetic cannabinoid with properties that make it an appealing candidate as a postoperative nausea and vomiting (PONV) prophylactic adjunct. Nabilone has proven clinical utility in chemotherapy-related nausea and vomiting but has not been adequately tested for PONV. The purpose of this study was to evaluate the effectiveness of a single dose of nabilone for the prevention of PONV.

Methods: This was a pragmatic single-centre randomized-controlled trial comparing oral nabilone vs placebo for the prevention of PONV. Eligible patients scheduled for elective surgery under general anesthesia who had a preoperative risk of PONV greater than 60% received either nabilone 0.5 mg or placebo orally prior to surgery. As part of the pragmatic design, the study medication was given in addition to any other combination of antiemetic prophylaxis. The primary outcome was the incidence of PONV. Secondary outcomes included the effect on pain, speed of recovery, and drug side effects.

Results: Of the 340 patients randomized, 172 received nabilone and 168 received placebo. There was no difference in the incidence of PONV, which occurred in 20.9% in the nabilone group and 21.4% in the placebo group (relative risk, 0.98; 95% confidence interval, 0.89 to 1.11; P = 0.99). There were also no differences in pain scores, opioid consumption, or reported drug side effects.

Conclusion: Oral nabilone 0.5 mg given as a single dose prior to surgery is ineffective in reducing PONV. This trial was registered at ClinicalTrials.gov, identifier: NCT02115529.