How effective is cannabis for chemotherapy-induced nausea and vomiting?

This is one of the best-supported indications for cannabinoids. The brainstem dorsal vagal complex and nucleus tractus solitarius — key emesis control centers — express CB1 receptors that, when activated, suppress vomiting. Dronabinol and nabilone are FDA-approved for chemotherapy-induced nausea and vomiting (CINV) refractory to standard antiemetics. A 2001 Cochrane review of 30 RCTs found cannabinoids superior to placebo and comparable to older antiemetics (prochlorperazine, metoclopramide) for CINV. However, modern 5-HT3 antagonists (ondansetron) and NK1 antagonists (aprepitant) are more effective and better tolerated than cannabinoids for most patients. Cannabinoids remain a useful option for refractory CINV or as add-on therapy. Smoked/vaporized cannabis has not been studied in controlled CINV trials — only pharmaceutical cannabinoids have RCT evidence.