Efficacy of dronabinol alone and in combination with ondansetron versus ondansetron alone for delayed chemotherapy-induced nausea and vomiting.

To compare the efficacy and tolerability of dronabinol, ondansetron, or the combination for delayed chemotherapy-induced nausea and vomiting (CINV) in a 5-day, double-blind, placebo-controlled study. Patients receiving moderately to highly emetogenic chemotherapy received dexamethasone (20 mg PO), ondansetron (16 mg IV) and either placebo or dronabinol (2.5 mg) prechemotherapy on day 1. Patients randomized to active treatment (dronabinol and/or ondansetron) also received dronabinol (2.5 mg) after chemotherapy on day 1. On day 2, fixed doses of placebo, dronabinol (10 mg), ondansetron (16 mg), or combination therapy were administered. On days 3-5, patients received placebo, flexible doses of dronabinol (10-20 mg), ondansetron (8-16 mg), or dronabinol and ondansetron (10-20 mg dronabinol, 8-16 mg ondansetron). Total response (TR = nausea intensity <5 mm on visual analog scale, no vomiting/retching, no rescue antiemetic), nausea (occurrence and intensity) and vomiting/retching episodes. Sixty-four patients were randomized; 61 analyzed for efficacy. TR was similar with dronabinol (54%), ondansetron (58%), and combination therapy (47%) versus placebo (20%). Nausea absence was significantly greater in active treatment groups (dronabinol, 71%; ondansetron, 64%; combination therapy, 53%) versus placebo (15%; p < 0.05 vs. placebo for all). Nausea intensity and vomiting/retching were lowest in patients treated with dronabinol. Active treatments were well tolerated. The low number of patients due to slow enrollment limits the interpretation of these data. Dronabinol or ondansetron was similarly effective for the treatment of CINV. Combination therapy with dronabinol and ondansetron was not more effective than either agent alone. Active treatments were well tolerated.