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Takuma Higurashi, Akiko Fuyuki, Hidenori Ohkubo, Hiroshi Iida, Masahiko Inamori, Masataka Taguri, Yasuhiko Komiya, Shungo Goto, Leo Taniguchi, Naoya Okada, Takafumi Ito, Akira Mizuki, Noriaki Manabe, Ken Haruma, Mitsuo Nagasaka, Yoshihito Nakagawa, Naoki Ohmiya, Sayuri Yamamoto, Yasushi Funaki, Kunio Kasugai and Atsushi Nakajima
Background: Irritable bowel syndrome (IBS) is a common gastrointestinal functional disorder characterized by abdominal pain and altered bowel habits in the absence of any structural abnormality. IBS patients often suffer from abdominal symptoms and severe reduction in quality of life (QOL). The Kampo formula keishikashakuyakuto (KST) is considered effective for IBS abdominal pain. However, there are few high-quality randomized controlled trials of Kampo treatment of IBS. Methods: This will be a multicenter, double-blind, placebo-controlled, randomized controlled trial using patients who fulfil the Rome IV criteria for IBS. All eligible patients will be randomly allocated into either a KST group or a placebo group. Patients in the KST group will receive an oral dose of 2.5 g KST three times per day before or between meals for 8 weeks. Patients in the placebo group will receive placebo medicine with the same frequency as the KST group. IBS-QOL and IBS severity index scores for the two groups will be compared before and after treatment. Discussion: This will be the first study to assess the effect of KST on QOL in IBS patients. Kampo medicine is believed to improve IBS-associated symptoms; however, its mechanism of efficacy is still unknown. Clear evidence that KST is effective for IBS would expand the therapeutic options for the disease and have a substantial clinical impact. Registration: This trial has been registered in the University Hospital Medical Information Network Clinical Trials Registry as UMIN000026235. Funding: Research for creating scientific knowledge about Kampo medicine from the Japan Agency for Medical Research and Development.