Since there is no registered anthelmintic drug available for use in goats, extra-label use of drugs is a common practice in most
countries. The aim of the present study was to compare the pharmacokinetic disposition of levamisole (LVM)-oxyclozanide
(OXZ) combination in sheep and goats following per os administration. Goats (n = 8) and sheep (n = 8) 12- to 16-months-old were
used for this study. The animals received tablet formulation of LVM and OXZ combination orally at a dose of 7.5 mg/kg and
15 mg/kg body weight, respectively. Blood samples were collected by jugular vein at different times between 5 min and 120 h
after drug administrations. The plasma concentrations of LVM and OXZ were analyzed by HPLC following liquid-liquid phase
extraction procedures. The plasma concentrations and systemic availabilities of both LVM and OXZ in goats were lower and the
plasma persistence of LVM was shorter compared with those observed in sheep. Terminal half-lives (t1/2z) of both molecules
are shorter in goats compared with those in sheep. Goats treated with LVM-OXZ combination at the recommended dose for
sheep may result in a reduced efficacy, because of under-dosing, which may increase the risk of drug resistance in parasites.
Increased or repeated dose could be a strategy to provide higher plasma concentration and thus to improve the efficacy against
the target parasites in goats compared with sheep. However, some adverse reactions may occur since LVM has relatively very
narrow therapeutic index due to its nicotine-like structure and effect
