Olanzapine-containing antiemetic therapy for the prevention of carboplatin-induced nausea and vomiting Abstract Purpose There remains an unmet clinical need for the control of chemotherapy-induced nausea and vomiting (CINV), particularly in the prevention of nausea and the delayed phase control. We evaluated the efficacy and safety of antiemetic therapy with olanzapine, a neurokinin-1 receptor antagonist, a 5-hydroxytryptamine-3 (5-HT3) receptor antagonist and dexamethasone in patients receiving carboplatin-containing chemotherapy. Olanzapine inhibits signalling via multiple neurotransmitter receptors involved in CINV. Methods Chemotherapy-naïve patients with lung cancer who received carboplatin-containing chemotherapy were enrolled in this phase-II study. Patients received olanzapine, aprepitant, a 5-HT3 receptor antagonist and dexamethasone. The primary endpoint was the complete response rate (no vomiting and no rescue therapy) during 120 h after administration of chemotherapy agents. Results Thirty-three patients received olanzapine-containing antiemetic therapy. The overall complete response rate was 93.3% (95% confidence interval, 80.4–98.3%). The frequency of nausea was 15.2% in the delayed phase and 18.2% in the overall phase. Somnolence was observed in 16 patients. Conclusion Adding olanzapine to antiemetic therapy with aprepitant, a 5-HT3 receptor antagonist and dexamethasone improved CINV control in patients receiving carboplatin-containing chemotherapy.