A comparative study between excess-dose users and regular-dose users of rhubarb contained in Kampo medicines

With prolonged use of rhubarb-containing Kampo medicines, some patients come to ask for high-dose rhubarb because of deteriorated reactivity to rhubarb. We divided patients into two groups in terms of rhubarb-dose, and compared clinical backgrounds between regular-dose group and excess-dose group. Patients who were treated with rhubarb-containing Kampo extracts (manufactured prescriptions) or Kampo formulae (decoctions) for more than 12 months were enrolled. These two groups were compared for age, sex, shape of stool, abdominal symptoms, existence of hemorrhoids, Kampo diagnosis of abdomen, past stimulant laxative use, duration of stimulant laxative use before the first administration of rhubarb, duration of rhubarb use in our hospital, and initial existence of stimulant pain caused by taking stimulant laxatives for the first time. No significant difference was shown between the two groups in terms of age, duration of stimulant laxative-use before the first prescription of rhubarb, shape of stool, abdominal symptoms, existence of hemorrhoids, or duration of rhubarb-use. However, most patients in the regular-dose group had initial stimulant pain of the abdomen upon taking stimulant laxatives for the first time, but most patients in the excess-dose group did not (p < 0.001). All patients except one in the regular dose group had the sign of "umbilical region tenderness on pressure", but half of the excess-dose group did not have it (p = 0.041). Based on these findings, the absence of "initial stimulant pain" and the absence of "umbilical region tenderness on pressure" may predict increasing or excess use of rhubarb, and long-term use of rhubarb should be discouraged more strongly in the patients without these signs.