Efficacy of pharmacokinetic interactions between piperonyl butoxide and albendazole against gastrointestinal nematodiasis in goats.

To test the hypothesis that modulation of hepatic microsomal sulphoxidation and sulphonation by the cytochrome P450 inhibitor piperonyl butoxide could increase bioavailability of albendazole, the present study was undertaken to understand the pharmacokinetics of albendazole in goats at a dose of 7.5 mg kg- 1 body weight with and without co-administration with piperonyl butoxide at 63.0 mg kg- 1 body weight. Plasma albendazole sulphoxide metabolite, the anthelmintically active moiety, reached its maximum concentration of 0.322 ± 0.045 µg ml- 1 and 0.384 ± 0.013 µg ml- 1 at 18 h and 24 h after administration of albendazole alone and co-administration of albendazole with piperonyl butoxide, respectively. Analysis of the data revealed statistically increased albendazole sulphoxide levels at 24 (P 0.05) in values of maximum concentration (normal and calculated) could be observed between groups of goats. However, values of time to reach the concentration maximum (normal and calculated), area under the concentration-time curve (0-∞ and calculated), minimum residence time, distribution half-life, elimination half-life and total area under the first movement of plasma drug concentration-time curve were significantly higher (P <  0.05) in plasma levels of albendazole sulphoxide in goats following single oral co-administration of albendazole with piperonyl butoxide. The faecal egg count reduction and lower 95% confidence limit for the group treated with albendazole alone were 97 and 68%, while for co-administration of albendazole and piperonyl butoxide the values were 99 and 97%, respectively. The ED50 for egg hatch was 0.196, indicating suspected resistance to benzimidazole anthelmintics. The drug combination proved efficacious against an albendazole-resistant nematode parasite population in goats.

Diet-induced modulation of pharmacokinetics of albendazole in Sahiwal cattle.

The influence of diet type and pre-treatment fasting on the kinetic disposition of albendazole was evaluated in Sahiwal heifers following oral and intra-ruminal administration of the drug. The anthelmintically active moiety albendazole sulphoxide appeared early and was eliminated early in cattle offered green fodder, with decreased maximum concentration (C max) and area under concentration-time curve (AUC) when the drug was administered both through oral and intra-ruminal routes. Further, the elimination half-life (t ½ß) revealed significantly increased values for albendazole sulphoxide in cattle administered albendazole through the intra-ruminal route. An increased AUC and t ½ß is reflective of increased bioavailability of albendazole in animals offered dry fodder. Increased values (P <  0.05) of C max, time to C max (T max), AUC and t ½ß for albendazole sulphoxide occurred in cattle with a pre-treatment 24-h fast, resulting in its increased bioavailability. Extrapolation of data of the active metabolite albendazole sulphoxide levels in terms of drug-parasite contact revealed increased exposure of parasites to the drug in cattle administered albendazole through the intra-ruminal route and with 24-h pre-treatment fasting.