Pharmacokinetics of cyclosporine in woodchucks and Pekin ducks

The purpose of this study was to evaluate the pharmacokinetics of cyclosporine (Cy) in woodchucks ( Marmota monax ) and Pekin ducks. These data are needed to design rational dosing regimens. Pharmacokinetic parameters were calculated from blood concentration-time data obtained following intravenous (i.v.) administration of 10 mg/kg body weight to woodchucks and Pekin ducks. Whole blood samples were collected in EDTA and assayed using a commercially available radioimmunoassay kit that employs a monoclonal antibody specific for Cy. The blood concentration-time profile best Dtted an open, two-compartmental model in Pekin ducks. Compartmental analysis of data in woodchucks did not adequately describe the data. When non-compartmental pharmacokinetic analysis of the data was performed, the resulting mean (± SD) pharmacokinetic parameters in woodchucks and Pekin ducks, respectively, were as follows: volume of distribution at steady-state, 2.9 (± 0.8) and 2.7 (± 0.2) L/kg; systemic clearance, 10.2 (± 2.8) and 28.6 (± 6.1) mL/kg/min; mean residence time, 4.8 (± 1.1) and 1.6 (± 0.3). These data suggest that Pekin ducks clear Cy at a faster rate than do woodchucks and that a greater dose of Cy should be administered to Pekin ducks in order to achieve adequate immunosuppression.