Eprinomectin in dairy zebu Gobra cattle (Bos indicus): plasma kinetics and excretion in milk

The pharmacokinetics and mammary excretion of eprinomectin were determined in zebu Gobra following topical administration of 0.5 mg kg(-1). The kinetics of plasma and milk was analysed using a one-compartment model. The maximum plasma concentration of 8.83+/-2.15 ng ml(-1) occurred 1.30 days post-administration. The area under the plasma concentration-time curve was 30.63+/-5.56 ng day(-1) ml(-1) and the mean residence time was 3.38+/-0.60 days. Eprinomectin was detected in milk at the first sampling time and thereafter for at least 8 days. The systemic availability of eprinomectin was significantly lower than that for other breeds of cattle. Comparison of the milk and plasma data demonstrated the parallel disposition of the drug in the milk and plasma with a milk/plasma ratio of 0.094. The very low extent of mammary excretion supports the permitted use of eprinomectin in lactating zebu Gobra.