Comparative pharmacokinetics of fenbendazole in buffalo and cattle

Pharmacokinetics of fenbendazole following intravenous and oral administration to pigs

OBJECTIVE

To determine pharmacokinetics and metabolic patterns of fenbendazole after IV and oral administration to pigs.

ANIMALS

4 mixed-breed female pigs weighing 32 to 45 kg.

PROCEDURE

Fenbendazole was administered IV at a dose of 1 mg/kg. One week later, it was administered orally at a dose of 5 mg/kg. Blood samples were collected for up to 72 hours after administration, and plasma concentrations of fenbendazole, oxfendazole, and fenbendazole sulfone were determined by use of high-pressure liquid chromatography. Plasma pharmacokinetics were determined by use of noncompartmental methods.

RESULTS

Body clearance of fenbendazole after IV administration was 1.36 L/h/kg, volume of distribution at steady state was 3.35 L/kg, and mean residence time was 2.63 hours. After oral administration, peak plasma concentration of fenbendazole was 0.07 microg/ml, time to peak plasma concentration was 3.75 hours, and mean residence time was 15.15 hours. Bioavailability of fenbendazole was 27.1%. Oxfendazole was the major plasma metabolite, accounting for two-thirds of the total area under the plasma concentration versus time curve after IV and oral administration. Fenbendazole accounted for 8.4% of the total AUC after IV administration and 4.5% after oral administration.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that fenbendazole was rapidly eliminated from plasma of pigs. The drug was rapidly absorbed after oral administration, but systemic bioavailability was low.

Efficacy and pharmacokinetics of triclabendazole in buffalo with induced fasciolosis

A study was conducted to understand pharmacokinetics and flukicidal activity of intraruminal administration of triclabendazole (TCBZ) at 12.0, 24.0 and 36.0 mg kg-1 body weight in experimentally Fasciola gigantica-infected buffaloes on Week 2 and 10 post-infection. No fluke eggs in faeces and no flukes could be recovered from the liver of buffaloes following intraruminal administration of triclabendazole at 24.0 and 36.0 mg kg-1 body weight both on Weeks 2 and 10 post-infection, while the recommended therapeutic dose at 12.0 mg kg-1 body weight was 19-23% effective. Pharmacokinetic analysis of the data revealed a significantly higher (P < 0.05) concentration maximum of both the metabolites and area under concentration-time curve of TCBZ-SO2 in animals treated at 12.0 mg kg-1 body weight on Week 10 post-infection, whereas a significantly higher area under the concentration-curve and elimination half-life of both the metabolites and significantly higher concentration maximum and area under the concentration-time curve of both the metabolites were observed in animals treated on Week 10 post-infection at the dose rates of 24.0 and 36.0 mg kg-1 body weight, respectively. Bioavailability of triclabendazole was more in buffaloes with mature flukes than with immature flukes.

Influence of diet type on the kinetic disposition of fenbendazole in cattle and buffalo

The plasma concentration profiles of fenbendazole (FBZ), FBZ-sulphoxide and FBZ-sulphone were measured following intraruminal administration of FBZ at 7.5 mg kg-1 body weight in cattle and buffalo offered 3 different diets: 100% dry mature sorghum hay, 100% green Pennisetum spp. and a 50:50 mix of these 2 diets. Changing the diet from dry to green fodder resulted in significantly lower systemic availability of FBZ and its metabolites in both species. Buffalo had a lower systemic availability of the drug than cattle on the dry diet and the difference between species increased when the diet included green fodder. It is suggested that decreased transit time of digesta on the green fodder reduced systemic concentrations by reducing the time available for gastrointestinal absorption of the drug.