Comparison of olanzapine 2.5 mg and 5 mg in the prevention of chemotherapy-induced nausea and vomiting: a Japanese nationwide database study

Background Olanzapine is prescribed as prophylaxis for chemotherapy-induced nausea and vomiting at a dose of 2.5 or 5 mg in Asian countries. We compared the effectiveness of olanzapine 2.5 mg and 5 mg in preventing chemotherapy-induced nausea and vomiting among patients receiving high-emetogenic chemotherapy for lung cancer. Methods Using a Japanese national inpatient database, we identified patients who received olanzapine doses of 2.5 or 5 mg during high-emetogenic chemotherapy for lung cancer between January 2016 and March 2021. We conducted a 1:1 propensity score-matched analysis with adjustment for various factors, including those affecting olanzapine metabolism. The outcomes were additional antiemetic drug administration (within 2-5 days after chemotherapy initiation), length of hospital stay, and total hospitalization costs. Results Olanzapine 2.5 and 5.0 mg were used in 2905 and 4287 patients, respectively. The propensity score-matched analysis showed that olanzapine 2.5 mg administration was significantly associated with a higher proportion of additional antiemetic drug administration (36% vs. 31%, p < 0.001) than olanzapine 5 mg. The median length of hospital stay was 8 days in both groups. Total hospitalization cost did not differ significantly between the two doses of olanzapine (5061 vs. 5160 USD, p = 0.07). The instrumental variable analysis demonstrated compatible results. Conclusion Prophylactic use of olanzapine 2.5 mg during chemotherapy for lung cancer was associated with a higher rate of additional antiemetic drugs than olanzapine 5 mg.