Effect of Orally Administered Shao-Yao-Gan-Cao-Tang (Shakuyaku-kanzo-to) on Muscle Cramps in Maintenance Hemodialysis Patients: A Preliminary Study

Muscle cramps are one of the most common complications of hemodialysis (HD), and often are a source of great pain in spite of various clinical measures. The traditional herbal medicine, shao-yao-gan-cao-tang (Japanese name: Shakuyaku-kanzo-to), consists of equal amounts of paeony and licorice roots, and has been used in Japan and China for muscle pain or skeletal muscle tremors. To determine whether this medicine is able to prevent frequent and unendurable muscle cramps in patients undergoing HD, Shakuyaku-kanzo-to at 6 g per day was prospectively administered for 4 weeks to five patients on HD who were suffering from frequent muscle cramps. The frequency and severity of cramping before and after the treatment treatment were carefully observed and compared. Skeletal muscle cramps completely disappeared in two of the treated patients after the start of oral administration of Shakuyaku-kanzo-to. Moreover, the frequency of cramping was significantly decreased in two of the remaining three patients after persistent administration. The severity of muscle cramps was also decreased by this treatment in the responsive patients. No serious side effects were detected during the treatment period. The inhibitory effect of Shakuyaku-kanzo-to on muscle contraction was also experimentally examined by using phrenic nerve-diaphragm preparations from male Wistar rats. Differences between the twitch responses were determined when the diaphragms and the nerves were stimulated in the presence and absence of the extract of Shakuyaku-kanzo-to. The results demonstrated that extracts of paeony and licorice roots inhibit contraction of skeletal muscles in rats. Taken together, we suggest that administration of Shakuyaku-kanzo-to is a safe, effective treatment for preventing muscle cramps in patients undergoing HD.