Dose-dependent Efficacy of Olanzapine for Chemotherapy-induced Nausea and Vomiting: A Systematic Review and Meta-analysis.

Background/aim: This study aimed to investigate the efficacy of olanzapine, an antiemetic agent used to prevent chemotherapy-induced nausea and vomiting (CINV), at 5 and 10 mg/day, by chemotherapy emetogenic risk, and to evaluate the efficacy of low dose olanzapine at 2.5 mg/day.

Materials and methods: PubMed and Web of Science were searched to identify studies evaluating the efficacy of olanzapine in CINV prevention from database inception up to August 31, 2023. The primary endpoints were complete response (CR, defined as no emesis and no rescue) rates in acute, delayed, and overall phases. Additionally, data on the efficacy of 2.5 mg/day olanzapine were evaluated.

Results: A total of 24 studies were included in the meta-analysis. The CR rates in acute, delayed, and overall phases were 91% [95% confidence interval (CI)=88-94%], 76% (95%CI=71-80%), and 72% (95%CI=67-77%), respectively. Subgroup analysis in studies on highly emetogenic chemotherapy (HEC) revealed the CR rates in acute, delayed, and overall phases were not significantly different between 5 and 10 mg/day olanzapine. Conversely, the CR rates in delayed and overall phases were significantly better with 5 mg/day olanzapine in studies on moderately emetogenic chemotherapy (MEC) (p =0.03 and p=0.04, respectively). Evaluation of olanzapine at 2.5 mg/day suggested that it is effective in CINV prevention.

Conclusion: Olanzapine was effective at both 5 and 10 mg/day in patients receiving HEC or MEC; its efficacy was not dose-dependent. Reduced olanzapin dose at 2.5 mg/day could be considered as an option for the management of CINV.