Concentration time course of praziquantel in Filipinos with mild Schistosoma japonicum infection.

Despite extensive use of praziquantel, the current drug of choice for the treatment of schistosomiasis and other helminthic infections, little information is available about its pharmacokinetics in individuals living in geographic areas where such infections are endemic. We investigated the pharmacokinetics of praziquantel by determining its serum concentration-time course in four selected Filipino volunteers with mild Schistosoma japonicum infection who lived in an endemic area in the Southern Philippines. At specified intervals during a 24-hour time period after a single oral dose of praziquantel (25 mg/kg BW), intravenous samples of blood were drawn, processed and analyzed for praziquantel using reverse phase high pressure liquid chromatography. The same study was repeated one week later to assess pharmacokinetic reproducibility. A third study, simulating current field practice, consisted of dosing the patient four hours apart and analyzing for praziquantel in serial blood samples drawn at specified time intervals after the first and second dose. The following results were obtained: 1) Serum concentration-time course of praziquantel was reproducible for each patient but varied from patient to patient. 2) Praziquantel was rapidly absorbed in the gastrointestinal tract as measurable amounts appeared in the blood as early as 15 minutes after dosing. Time to peak serum concentration ranged from 1.50 to 6.00 hours with almost complete elimination from blood by 24 hours whether it was administered as a single dose (1 x 25 mg/kg BW) or as a twice a day dose (2 x 25 mg/kg BW) 4 hours apart. Half-life values ranged from 1.00 to 2.50 hours.(ABSTRACT TRUNCATED AT 250 WORDS)