Some pharmacokinetic parameters of eprinomectin in goats following pour-on administration

Some pharmacokinetic parameters of eprinomectin were determined in goats following topical application at a dose rate of 0.5 mg/kg. The plasma concentration versus time data for the drug were analysed using a one-compartment model. The maximum plasma concentration of 5.60 +/- 1.01 ng/ml occurred 2.55 days after administration. The area under the concentration-time curve (AUC) was 72.31 +/- 11.15 ng day/ml and the mean residence time (MRT) was 9.42 +/- 0.43 days. Thus, the systemic availability of eprinomectin to goats was significantly lower than that for cows. The low concentration of eprinomectin in the plasma of goats suggests that the pour-on dose of 0.5 mg/kg would be less effective in this species than in cows. Further relevant information about the optimal dosage and residues in the milk of dairy goats is needed before eprinomectin should be used in this species.