Shakuyaku-kanzo-to (Shao-Yao-Gan-Cao-Tang) as treatment of painful muscle cramps in patients with lumbar spinal stenosis and its minimum effective dose

Shakuyaku-kanzo-to (Shao-Yao-Gan-Cao-Tang) is a Kampo medicine, which is known to be effective against muscle cramps as well as crampy pain in the gastrointestinal smooth muscle and skeletal muscle. However, glycyrrhizin in this medicine also causes adverse drug reactions such as hypokalemia, hypertension, and edema. We analyzed the therapeutic efficacy of Shakuyaku-kanzo-to for painful muscle cramps associated with lumbar spinal stenosis and clarified its minimum effective dose. 58 patients with lumbar spinal stenosis and painful muscle cramps were included. We evaluated the therapeutic efficacy of Shakuyaku-kanzo-to (n=16) comparing with eperisone hydrochloride (n=14). We then examined the minimum effective dose of Shakuyaku-kanzo-to in the remaining 28 patients. Shakuyaku-kanzo-to reduced the frequency of painful muscle cramps to less than 50% in 13 of 16 patients. However, eperisone hydrochloride reduced it to the same level in 4 of 14 patients. The onset of the maximum therapeutic effect of Shakuyaku-kanzo-to was less than 3 days from the start of treatment in 11 of 15 patients. Regarding the minimum effective dose for painful muscle cramps, 2.5 g of Shakuyaku-kanzo-to used as needed had a therapeutic effect that was equivalent to the regular use of 7.5 g/day (given in divided doses three times daily). Our data show that Shakuyaku-kanzo-to is effective for painful muscle cramps associated with lumbar spinal stenosis. The dosage of 2.5 g of Shakuyaku-kanzo-to as needed had a therapeutic effect that was equal to the regular use of 7.5 g/day.