Impact of drug dosage and brand on bioavailability and efficacy of praziquantel

The efficacy of two brands (brand 1=Billricide; Bayer AG, Leverkusen, Germany; brand 2=Distocide; EPICO pharmaceuticals, Cairo, Egypt) of praziquantel (PZQ) in full and half doses (40 and 20 mg kg-1 monitored as percentage egg reduction and cure rate was investigated in S. mansoni infected school-children. A total of 506 school-children (8-16 years of age) were classified into three groups according to their intensity of infection, heavy [>500 eggs per grams (epg)], moderate (100-500 epg) and light (<100 epg), after examination of three stool samples (three slides per sample) on three consecutive days. Percentage egg reduction and cure rate were monitored 4 and 10 weeks post-treatment for each dose regimen in the different test groups. Before testing the efficacy of either brand in patients, the pharmacokinetic parameters of the two brands were studied in non-infected normal volunteers. Statistical analysis of the pharmacokinetic parameters of brand 1 vs brand 2 (in a dose of 20 or 40 mg kg-1) revealed no significant difference in elimination (ke), absorption rate constant (ka), elimination half life (tl/2e), area under the time-concentration curve (Auc), serum maximum concentration (Cpmax) and time to maximum concentration (Tmax). As regards the efficacy of test drugs, statistical analysis revealed that up to 10 weeks post-treatment tre two brands of PZQ in full dose were equally effective in reducing egg count as their half doses except in heavily infected cases treated with brand 2 of PZQ. In this group a significantly higher percentage of egg reduction was recorded in patients receiving 40 mg kg-1 when compared to those treated with 20 mg kg-1. Considering patients cured (passing no viable eggs), higher doses of brand 1 and brand 2 produced in several instances a higher percentage of cures than lower doses. However comparison of brand 1 to brand 2 of PZQ whether in full or half dose did not reveal any statistically significant difference in either the cure rate or percent egg reduction. © 1995.