RESEARCH Open Access i e

are widely used and researched in the USA and Europe [1,2]. One of the underlying reasons for this is to reduce the high costs of health care. There is a national health insurance system which enables everyone in Japan to re-ceive advanced health care at a low cost. Another char-acteristic of the health insurance system in Japan is that patients can access Western and Kampo medical care at the same time in the same medical institution [1,2]. Kampo, or traditional Japanese herbal medicine based on traditional Chinese herbal medicine, has been used for the treatment of not only acute but also chronic pain in Japan [3]. The Ministry of Health, Labor and Welfare of Japan, approves the use of 148 Kampo preparations (traditional herbal medicines) [4]. Currently, most Kampo preparations are prescribed as extract formulations of high quality. More-over, physicians who have studied Western medicine and Kampo medicine practice Western and Kampo medica