Pharmacokinetics of Ivermectin Administered Intravenously to Cattle

Ivermectin, a macrocyclic lactone disaccharide antiparasitic agent, was administered intravenously to six young calves (one bull, five steers) as a bolus dose of 200 μ/kg. The disposition kinetics of ivermectin in cattle can be described by a three-compartment open model with elimination from the central compartment. Compartmental analysis yielded mean parameters as follows: terminal elimination rate constant (β)=0.258 d−1, biological half-life (t1/2/β)=2.7 d; apparent volume of distribution of the central compartment (Vd1)=0.45 L/kg; apparent volume of distribution at steady state (Vdss)=2.4 L/kg. The area under the plasma concentration–time curve (AUC) was 254ng · d/mL. Noncompartmental parameters, obtained by utilizing statistical moment theory, mean residence time (MRT), clearance (CL), and Vdss were calculated to be 2.8 d, 0.79 L/kg · d, and 2.2 L/kg, respectively.