Single-dose pharmacokinetics of ampicillin/sulbactam (2:1) combination after intravenous administration to sheep and goats

Abstract The pharmacokinetic behaviour of a combination of ampicillin and sulbactam (2:1) in six sheep and six goats after single intravenous doses of 20 mg kg bodyweight −1 (13·33 mg kg −1 of ampicillin and 6·67 mg kg −1 of sulbactam) was investigated by using a high-performance liquid chromatographic method for determining plasma concentrations. The objective was to determine whether there are differences between sheep and goats in the disposition kinetics of ampicillin and sulbactam. The plasma concentration-time curves were analysed by compartmental pharmacokinetic and non-compartmental methods. The disposition curves for both drugs were best described by a biexponential equation (two-compartment open model) in both sheep and goats. The mean ( sd ) elimination half-lives of ampicillin were 0·32 (0·05) h in sheep and 0·32 (0·04) h in goats, and the half-lives of sulbactam were 0·74 (0·10) h and 0·79 (0·18) h in sheep and goats, respectively. The apparent volumes of distribution of ampicillin and sulbactam were similar in the two species. Mean ( sd ) body clearances of ampicillin were 0·69 (0·07) litre h −1 kg −1 in sheep and 0·72 (0·11) litre h −1 kg −1 in goats, and the body clearances of sulbactam were 0·38 (0·03) and 0·38 (0·07) litre h −1 kg −1 in sheep and goats, respectively. There were no significant differences between any of the pharmacokinetic parameters of ampicillin and sulbactam in the sheep and goats.