Double-blind studies of tolerance to praziquantel in Japanese patients with Schistosoma japonicum infections.

The first clinical trials of praziquantel against Schistosoma japonicum infections in Japan were planned to assess tolerance only. Three double-blind studies against placebo involving a total of 51 patients were conducted with dosages of praziquantel of 1 x 20 mg/kg body weight, 2 x 20 mg/kg, 3 x 20 mg/kg given on one day.The frequency of unwanted side effects was higher in the group of patients given praziquantel at a dose of 3 x 20 mg/kg than in all other drug- or placebo-treated patients. In general, the side effects, which included drowsiness, headache, lumbago, abdominal fullness, or epigastric discomfort, lasted for several hours but disappeared spontaneously. The results of laboratory tests showed no significant changes caused by treatment.The overall assessment showed excellent or good tolerance in all patients treated with praziquantel at the lower dose levels. In those given 3 x 20 mg/kg, tolerance was excellent in 1 of 12 patients, good in 9, and fair in 2, whereas the respective placebo-treated group showed excellent tolerance in 3 of 12, good in 7, and fair in 2.