The pharmacokinetics of eprinomectin in sheep following subcutaneous administration

The pharmacolcinetics of eprinomectin was determined in lactating sheep following subcutaneous administration at a dose rate of 0.2 mg kg(-1). The eprinomectin concentration in plasma was determined using High Performance Liquid Chromatography (HPLC) with a fluorescence detector. The kinetics of plasma concentrations were analysed using the non-compartment model. The maximum plasma concentration of 24.44 ng/mL occurred 2 days post-administration. Following subcutaneous administration of eprinomectin in sheep, the value of plasma elimination half-life, the area under the plasma concentration time curve (AUC) and mean residence time (MRT) were 388.52 +/- 0.25 h. 4282.10 ng.h/mL and 374.50 h, respectively. The values of Vd((area)), Vd((ss)) and CI(B) were 20.50 mL/kg, 13.70 mL/kg and 0.04 mL/h/kg, respectively. This study demonstrates that subcutaneous administration of eprinomectin led to higher bioavailability and longer mean residence time with a lower dose than a pour-on application, and that an injectable formulation may be applied in lactating sheep with zero withdrawal period.