Olanzapine as an add‐on, pre‐operative anti‐emetic drug for postoperative nausea or vomiting: a randomised controlled trial

Summary Postoperative nausea or vomiting occurs in up to 40% in patients with multiple risk factors, despite prophylaxis. Olanzapine is an antipsychotic drug that is used to prevent nausea and vomiting in palliative care and to treat chemotherapy‐induced nausea and vomiting. This study aimed to examine whether pre‐operative olanzapine, as a prophylactic anti‐emetic added to intra‐operative dexamethasone, ondansetron and total intravenous anaesthesia, reduced the incidence of postoperative nausea or vomiting. We performed a multiply‐blinded randomised controlled trial in patients aged 18–60 years with cancer at high risk of postoperative nausea or vomiting (three or four risk factors according to the Apfel criteria) plus a previous history of chemotherapy‐induced nausea and vomiting. Patients were allocated at random to receive 10 mg olanzapine or placebo orally 1 h before surgery in addition to a two‐drug regimen (dexamethasone and ondansetron) and propofol anaesthesia to prevent postoperative nausea or vomiting. The primary outcome was the incidence of postoperative nausea or vomiting in the first 24 h after surgery. In total, 100 patients were enrolled; 47 in the olanzapine group and 49 in the control group completed the study. The baseline characteristics of the groups were similar. The incidence of postoperative nausea or vomiting in the first 24 h after surgery was lower in the olanzapine group (12/47, 26%) than in the control group (31/49, 63%) (p = 0.008, RR 0.40 (95%CI 0.21–0.79)). Adding pre‐operative oral olanzapine to intra‐operative dexamethasone and ondansetron was highly effective in reducing the risk of postoperative nausea or vomiting in the first 24 hours after surgery in patients with a previous history of chemotherapy‐induced nausea and vomiting and at least three Apfel risk factors for postoperative nausea or vomiting.