Perspectives on the Use of Ninjin'yoeito in Modern Medicine: A Review of Randomized Controlled Trials

Background. Ninjin'yoeito (NYT), a traditional Japanese (Kampo) medicine that originates from China, has been used to treat qi and blood deficiency based on its original concept. Kampo medicine has been widely used to treat many conditions and disorders combined with western medicine or Kampo medicine alone in modern situation. Aims. We reviewed randomized controlled trials (RCTs) of NYT and discussed various standpoints regarding its use in modern situation. Methods. We searched PubMed, Cochrane Library, and Evidence Reports of Kampo Treatment (EKAT) for articles written in English, and Ichushi, J-Stage, and EKAT for those written in Japanese. Articles published before January 1, 2019, were retrieved using the keywords "ninjinyoeito" and "ninjin'yoeito," and RCTs were selected from these extracted articles. Result. Of 734 articles, 13 were RCTs, 46 were non-RCTs or studies of other designs, 15 were case reports, and 36 were experimental studies using NYT. NYT was evaluated for its use as a treatment for cancer and related conditions, refractory blood diseases and conditions, and otorhinolaryngologic symptom in 13 RCTs. Based on the use of Kampo medicine in modern situation called as Yasui's classification, 10 of 13 RCTs were categorized as "the side effects of Western medicinal treatment are mitigated when combined with Kampo treatment" and the remaining 3 were categorized as "treatment effect of Kampo medicine is increased in combination with standard Western medicinal treatment." Conclusion. Several studies demonstrated the efficacy of NYT in refractory diseases and other conditions, and the accompanied side effects of treatment with western medicine.