A review of frequently used Kampo prescriptions. Part 5. Rikkunshito

Background: The source of rikkunshito (RKT) is thought to be Yixuezhengzhuan by Yu Tuan. RKT was originally designed for many patients to treat gastrointestinal symptoms such as abdominal bloating, discomfort, nausea, and anorexia. Key Findings: RKT consists of eight types of crude drugs. Clinical studies including randomized clinical trials (RCT) for patients with non-erosive reflux disease (NERD) refractory to proton-pump inhibitor (PPI) have demonstrated that RKT improves not only acid-related dysmotility symptoms, but also extra-esophageal symptoms, and with RCT trial for functional dyspepsia (FD), RKT can simultaneously treat gastrointestinal and psychological symptoms. Moreover, RKT was recently applied to the day-to-day conditions, post-operative management, and chemotherapy in cancer patients. Preclinical studies have also reported that various pharmacological functions of RKT such as its protective effect on mucosal injuries and its prokinetic effect on gastrointestinal tract motility have been elucidated. RKT was considered to increase plasma ghrelin levels by the inhibition of 5-HT_2B and 5-HT_2C receptor activities, enhanced ghrelin-mediated signaling, inhibited degradation of acylated ghrelin to suppress decreases in plasma ghrelin levels by inhibiting the rate of degradation of acyl ghrelin to des-acyl ghrelin, and inhibited PDE III activity. The incidence of adverse events associated with RKT was only 1.2%, and almost all adverse drug reactions were non-serious reactions. Conclusion: RKT is one of the very good candidates for beneficial medicines especially for patients presenting with intractable symptoms caused by gastrointestinal diseases such as disorders of gut–brain interaction or cancers.