Eprinomectin in dairy goats: dose influence on plasma levels and excretion in milk

Abstract

The plasma levels and milk excretion of eprinomectin were determined in goats following topical application at doses of 0.5 mg kg⁻¹ and 1.0 mg kg⁻¹. The area under the concentration–time curve (AUC) was 2 times lower for 0.5 mg kg⁻¹ (8.24 ± 3.50 ng day⁻¹ ml⁻¹) than for 1.0 mg kg⁻¹ (15.68 ± 8.84 ng day⁻¹ ml⁻¹), suggesting that the pharmacokinetics of eprinomectin in goats is dose independent. The bioavailability of eprinomectin in lactating compared with non-lactating goats is low. This is probably due to the physiological status of dairy animals, which present a marked decrease in body fat. Comparison of the eprinomectin concentrations in the milk and plasma demonstrated a parallel disposition of the drug with a milk-to-plasma ratio of 0.10–0.25. The amount of drug recovered in the milk was 0.3–0.5% of the total administered dose. In all cases, the maximum level of residue in milk remained below the maximum acceptable level of 30 ng ml⁻¹ permitted in lactating cattle.