Pharmacokinetics of a novel formulation of ivermectin after administration to goats

Objective-To evaluate the pharmacokinetics of a novel commercial formulation of ivermectin after administration to goats. Animals-6 healthy adult goats. Procedure-Ivermectin (200 mu g/kg) was initially administered IV to each goat, and plasma samples were obtained for 36 days. After a washout period of 3 weeks, each goat received a novel commercial formulation of ivermectin (200 mu g/kg) by SC injection. Plasma samples were then obtained for 42 days. Drug concentrations were quantified by use of high-performance liquid chromatography with fluorescence detection. Results-Pharmacokinetics of ivermectin after IV administration were best described by a 2-compartment open model; values for main compartmental variables included volume of distribution at a steady state (9.94 L/kg), clearance (1.54 L/kg/d), and area under the plasma concentration-time curve (AUC; 143 [ng(circle)d]/mL). Values for them noncompartmental variables included mean residence time (737 days), AUC (153 [ng(circle)d]/mL), and clearance (1.43 L/kg/d). After SC administration, noncompartmental pharmacokinetic analysis was conducted. Values of the variables calculated by use of this method included maximum plasma concentration (C-max; 21.8 ng/mL), time to reach C-max (3 days), and bicavailability (F; 91.8%). Conclusions and Clinical Relevance-The commercial formulation used in this study is a good option to consider when administering ivermectin to goats because of the high absorption, which is characterized by high values of F In addition, the values of C-max and time to reach C-max are higher than those reported by other investigators who used other routes of administration.