Pharmacokinetics of selamectin in helmeted guineafowl (Numida meleagris) after topical administration

Twenty-one healthy helmeted guineafowl (Numida meleagris) housed at the Oklahoma City Zoo were used to evaluate the pharmacokinetic parameters of topical selamectin. Birds were divided randomly into three groups of seven birds each. On day 1, all birds received one dose of 20 mg/kg selamectin topically. Based on the group number, blood was collected from each bird on three separate occasions over a 28-day period. Plasma using liquid chromatography with mass spectrometry was used to determine selamectin concentrations. Mean plasma terminal half-life and maximum plasma concentrations of selamectin were 5.8 days and 16.1 ng/ml, respectively, with maximum plasma levels reached at 3 days. No adverse effects were detected. Birds in this study did reach and maintain plasma levels reported as therapeutic in other species for 19 days. Based on these results, selamectin may be a valuable antiparasiticide in some avian species.