Improvement of decocting method for Kampo medicines using a microwave oven to extend its applications in clinical practice

Decoction of Kampo medicines plays an important role in clinical practice, especially in individualized treatment, while the inconvenience and a long time requirement of the decocting process are impediments to its widespread use in Japan. In this study, we improved the decocting method by using a microwave oven such as those found in most kitchens. To validate the feasibility and safety of this new method, we decocted kakkonto, which is the most widely used formula in clinical treatment in Japan, and keishikabushito, which contains toxic components using a microwave oven. Regarding the contents of 8 characteristic components in the kakkonto decoction and the contents of 6 toxic components in the keishikabushito decoction as indices, and with the extraction and detoxification effects equal to those of the conventional decocting method as targets, we optimized the decocting conditions with Response Surface Methods. With this new method, it took 35 min to obtain almost the same extraction effect for kakkonto as with the conventional decocting method, which takes 40 min; meanwhile, it took only 45 min to detoxify keishikabushito, which takes 60 min using the conventional decocting method. Decocting Kampo medicines with a microwave oven is feasible and as safe as the conventional decocting method. It is a convenient, safe, time-saving method, and may be applied widely in clinical practice. This innovation should allow more patients to benefit from decoction and the individualized treatment it offers.