Preliminary clinical trials with praziquantel in Schistosoma japonicum infections in the Philippines.

Praziquantel, a new antischistosomal compound, was tested for tolerance and efficacy against placebo in two double-blind clinical trials in Philippine patients infected with Schistosoma japonicum.The compound was given orally at a dose of 3 x 20 mg/kg at intervals of 4 hours to a total of 82 patients-some without advanced disease and some with hepatosplenic involvement. A total of 43 patients received placebo. In a single-blind trial, 42 patients were given a single oral dose of 50 mg/kg. Monitoring of vital organ functions included comprehensive laboratory tests and serial electrocardiograms. In 38 patients with hepatosplenic involvement due to advanced stages of infection, serial electroencephalograms were additionally recorded. No toxic effects were observed in any of these examinations.Undesirable side effects occurred in 53% of the patients given 3 x 20 mg/kg and in 70% after a dose of 1 x 50 mg/kg. They consisted mainly of abdominal discomfort, fever, sweating, and occasionally giddiness, but in general were transient and mild. At 6 months post-treatment, 60 of 75 patients treated with 3 x 20 mg/kg and 29 of 41 treated with 1 x 50 mg/kg were completely negative for eggs. At 12 months post-treatment, 25 of 33 and 14 of 26 patients in the two treatment groups were cured. Thus the divided dosage gave a superior therapeutic result. Praziquantel proved to be free of major toxicity, and was well tolerated, highly effective, and easy to administer. Confirmation of results in extended trials may soon permit large-scale treatment.