Pharmacokinetics of nine sulphonamides in goats

Pharmacokinetics of nine sulphonamides was investigated in healthy goats. From the plasma disappearance curves after intravenous bolus injection clearance rates, plasma half-lives and distribution volumes were calculated. Plasma-protein binding was measured in vitro and in vivo. The highest-bound sulphonamides showed the highest concentration dependence of protein binding.
Plasma disappearance curves were in accordance with the one-, two- or three-compartment pharmacokinetic models. Disposition of sulphadimidine after 100 or 200 mg/kg and of sulphisomidine after 200 mg/kg showed limited enzyme capacity characteristics. Disposition of sulphadimidine, sulphisomidine and sulphadimethoxine was dose-dependent. Goats could also be divided in fast and slow sulphadimidine eliminators. Correlation was found only between clearance and half-life. Dosage regimens were calculated for seven sulphonamides.