Preliminary trials with praziquantel in human infections due to Schistosoma mansoni.

As part of a programme of multicentre trials of the tolerance and therapeutic effect of praziquantel, clinical trials were carried out in Brazil in patients with active Schistosoma mansoni infections, each of whom had a minimum geometric mean egg output of 100 eggs per gram of faeces calculated from multiple pretreatment stool examinations.The first stage was a double-blind assessment of tolerance and efficacy of oral doses of 1 x 20, 2 x 20, or 3 x 20 mg of praziquantel per kg of body weight. Subsequently, single-blind trials explored the effects of 3 x 20 mg/kg at 4-hourly intervals, and a single dose of 50 mg/kg.Side effects increased in frequency as dosage increased. Nausea, epigastric pain, headache, dizziness, and drowsiness were all noted but their severity was mild or moderate and they disappeared in 48 hours. In general, monitoring laboratory tests showed little change.Following a stringent parasitological follow-up, 96% of 28 patients followed at 1 year after treatment with either 3 x 20 mg/kg or 1 x 50 mg/kg were cured. Praziquantel seems to be a very promising drug against S. mansoni and further clinical trials should be strongly encouraged.