Comparative bioavailability of praziquantel tablets

Six different brands of 600 mg praziquantel tablets were evaluated. In vitro studies demonstrated that all but one of the products met the British Pharmacopoeia 1980 disintegration time specifications. The comparative bioavailability of four of the internationally available brands of praziquantel tablets were then studied in eight healthy volunteers using a crossover design. Serum praziquantel levels were determined by high-performance liquid chromatography. Individual serum profiles were analyzed for pharmacokinetic parameters such as maximum serum concentration, time to reach maximum, and area under the curve. Following administration of praziquantel 40 mg/kg po, the mean peak serum concentrations and the time to reach the peak ranged from 1.007 to 1.625 micrograms/ml and from 1.72 to 2.81 hours, respectively. The elimination half-life of praziquantel was 1.15 (0.94-1.25) hours. Differences greater than 20 percent (p less than 0.05) were noted for these parameters between the original brand and the generic formulations. The relative bioavailabilities of the generic praziquantel formulations, with respect to the original brand, were 91.25, 80.95, and 69.86 percent. This is due to the failure of disintegration and subsequently poor dissolution. The effect of 30 percent reduction of bioavailability may lead to unacceptably high rates of treatment failure.