Pharmacokinetic study of praziquantel administered alone and in combination with cimetidine in a single-day therapeutic regimen.

A brief therapeutic regimen of praziquantel, reduced to a single day, has been effective for treatment of neurocysticercosis. To study its pharmacokinetic characteristics, levels of praziquantel in plasma were determined for eight healthy volunteers after the administration of three oral doses of 25 mg/kg of body weight given at 2-h intervals, alone and with the simultaneous administration of cimetidine. Each volunteer received both regimens in a randomized crossover design. Blood samples were taken during a period of 12 h, and praziquantel concentration was measured by high-performance liquid chromatography. Levels of praziquantel in plasma remained above 300 ng/ml during a period of 12 h; they increased 100% when cimetidine was jointly administered. Compared with other regimens, the high levels obtained and the longer duration of action seem to be advantageous in prolonging the exposure of the parasites to the drug and support previous clinical experience showing that the treatment of neurocysticercosis with praziquantel can be reduced from 2 weeks to 1 day with the drug still retaining its cysticidal properties. Moreover, simultaneous administration of praziquantel and cimetidine could improve further the efficacy of the single-day therapy for cysticercosis and other parasitic diseases, such as schistosomiasis.