Kinetic disposition, systemic bioavailability and tissue distribution of salinomycin in chickens.

Salinomycin was administered to chickens orally and intravenously to determine blood concentration, kinetic behaviour, bioavailability and tissue residues. The drug was given by intracrop and intravenous routes in a single dose of 20 mg kg-1 body-weight. The highest serum concentrations of salinomycin were reached half an hour after oral dosage with an absorption half-life (t0.5(ab)) of 3.64 hours and elimination half-life (t0.5(beta)) of 1.96 hours. The systemic bioavailability percentage was 73.02 per cent after intracrop administration, indicating the high extent of salinomycin absorption from this route in chickens. Following intravenous injection the kinetics of salinomycin can be described by a two-compartment open model with a t1/2(alpha) of 0.48 hours, Vd ss (volume of distribution) of 3.28 litre kg-1 and Cl(beta) (total body clearance) of 27.39 ml kg-1 min-1. The serum protein-binding tendency of salinomycin as calculated in vitro was 19.78 per cent. Salinomycin concentrations in the serum and tissues of birds administered salinomycin premix (60 ppm) for two weeks were lower than those after administration of a single intracrop dose of pure salinomycin (20 mg kg-1 bodyweight). The highest concentration of salinomycin residues were present in the liver followed by the kidneys, muscles, fat, heart and skin. No salinomycin residues were detected in tissues after 48 hours except in the liver and these had disappeared completely by 72 hours.