Estimated incidence of adverse reactions to Kampo medicines in randomized controlled clinical trials

ABSTRACT Aim Japanese kampo medicines have a long history of empirical use but have not been clinically validated. Therefore, information about the incidence of adverse drug reactions (ADR) is usually lacking. We estimated the incidence of ADR from reports of randomized controlled trials of kampo products. Methods Trials of kampo products from the evidence reports of the kampo treatment database were examined to determine the number of patients treated with kampo products, and the number and type of ADR. Results Data for 20 340 users of kampo products were analyzed. Of ≥1000 patients who took kampo products, the proportions of those with ADR were as follows: bakumondoto, 2/2167 patients (0.09%); maobushisaishinto, 8/1201 patients (0.67%); saireito, 21/1131 patients (1.86%); daikenchuto, 5/1131 patients (0.44%); and rikkunshito, 23/1126 patients (2.04%). Five patients (0.02%) developed pseudoaldosteronism; all had received shakuyakukanzoto. Liver injury was reported in 32 patients (0.16%) and was approximately threefold higher in those treated with Scutellaria root formulae (15/4206; 0.36%) than in those treated with non‐Scutellaria formulae (17/16134; 0.11%). Of the Scutellaria root formulae, orengedokuto produced the highest incidence of liver injury (1.97%). No cases of interstitial pneumonia or mesenteric phlebosclerosis were reported. The ADR data for some formulae were similar to data from post‐marketing ADR surveys. Conclusion Examining data from a large number of trials is a useful way of estimating the incidence of kampo medicine ADR.