Antiemetic Effect of Rikkunshito, a Japanese Kampo Herbal Medicine, on Cisplatin-induced Nausea and Vomiting: A Nationwide Database Study in Japan

Objective The effect of Rikkunshito, a Japanese herbal Kampo medicine, on chemotherapy-induced nausea and vomiting (CINV) has been evaluated in several small prospective studies, with mixed results. We retrospectively evaluated the antiemetic effects of Rikkunshito in patients undergoing cisplatin-based chemotherapy using a large-scale database in Japan. Methods The Diagnosis Procedure Combination inpatient database from July 2010 to March 2019 was used to compare adult patients with malignant tumors who had received Rikkunshito on or before the day of cisplatin administration (Rikkunshito group) and those who had not (control group). Antiemetics on days 2 and 3 and days 4 and beyond following cisplatin administration were used as surrogate outcomes for CINV. Patient backgrounds were adjusted using the stabilized inverse probability of treatment weighting, and outcomes were compared using univariable regression models. Results We identified 669 and 123,378 patients in the Rikkunshito and control groups, respectively. There were significantly fewer patients using intravenous 5-HT-receptor antagonists in the Rikkunshito group (odds ratio, 0.38; 95% confidence interval, 0.16-0.87; p=0.023) on days 2 and 3 of cisplatin-based chemotherapy. Conclusion The reduced use of antiemetics on day 2 and beyond of cisplatin administration suggested a beneficial effect of Rikkunshito in palliating the symptoms of CINV.