Dose-dependent plasma disposition kinetics of albendazole in goats

As goats metabolize and eliminate anthelmintic compounds more rapidly from blood compared with sheep, a study was designed to compare the pharmacokinetics and bioavailability of albendazole (ABZ) metabolites in goats following oral administrations of ovine dose of 5 mg kg⁻¹ body weight and to investigate the effects of increased doses (7.5 and 10 mg kg⁻¹ body weight). The study revealed significantly (P<0.05) higher concentration maximum (C_max), area under concentration-time curve (AUC) and total area under the first movement of plasma drug concentration-time curve (AUMC) for albendazole sulphoxide (ABZ-SO) and albendazole sulphone (ABZ-SO₂) in goats administered ABZ at 7.5 and 10.0 mg kg⁻¹ body weight. Increased AUC had resulted in double relative bioavailability of both the metabolites in goats administered ABZ at higher doses. It was concluded that the dosing of goats with the sheep dose of ABZ is similar in consequence to under-dosing with the effect of allowing the heterozygote resistant worms to survive. As no significant difference in drug bioavailability was observed in goats administered 7.5 and 10.0 mg kg⁻¹ body weight, goats should be dosed with ABZ at least at 7.5 mg kg⁻¹ body weight to control gastrointestinal nematodes.