Effect of Shakuyaku-kanzo-to in patients with muscle cramps: A systematic literature review.

Background: Previous clinical studies have reported that Shakuyaku-kanzo-to (SKT) has a therapeutic effect on muscle cramps, but few studies have clarified how SKT acts to treat muscle cramps. The aim of this study was to perform an updated systematic review of clinical trials for SKT in patients with muscle cramps.

Methods: The literature was systematically reviewed to assess the effects of SKT in patients with muscle cramps. PubMed, Web of Science, Cochrane Library, Google Scholar, and Ichushi-Web were searched using the terms "Shakuyaku-kanzo-to" ("shakuyakukanzoto", etc), "clinical trials" and "muscle cramps". Two quality assessments were conducted independently by three authors. Data were extracted using a standardized extraction tool, and a qualitative synthesis of evidence was performed.

Results: Three randomized controlled articles were identified and enrolled in this study. A systematic review, but not a meta-analysis, was performed because of the high heterogeneity and limited number of studies. In patients with liver cirrhosis, the odds ratio (OR) for improvement with SKT compared to placebo was 1.27 (95% confidence interval [CI], 0.445-2.086) and compared to Goshajinkigan was 0.81 (95%CI, -1.734-0.114). The OR for improvement with SKT compared with eperisone hydrochloride in patients with lumbar spinal stenosis was 2.86 (95%CI, 0.980-4.744).

Conclusions: Current evidence appears insufficient to allow a meta-analysis of the effects of SKT, but SKT might show efficacy in treating muscle cramps in patients with cirrhosis or lumbar spinal stenosis.