Pharmacokinetics of an ampicillin/sulbactam (2:1) combination in rabbits

. Pharmacokinetics of an ampicillin/sulbactam (2:1) combination in rabbits. J. vet. Pharmacol. Therap.25, 259–264. The pharmacokinetics of a 2:1 ampicillin–sulbactam combination in six rabbits, after intravenous and intramuscular injection at a single dosage of 20 mg/kg bodyweight (13.33 mg/kg of sodium ampicillin and 6.67 mg/kg of sodium sulbactam) were investigated by using a high performance liquid chromatographic method for determining plasma concentrations. The plasma concentration–time curves were analysed by compartmental pharmacokinetic and noncompartmental methods. The disposition curves for both drugs were best described by an open two-compartment model after intravenous administration and a one-compartment model with first order absorption after intramuscular administration. The apparent volumes of distribution calculated by the area method for ampicillin and sulbactam were 0.62 ± 0.09 and 0.45 ± 0.05 L/kg, respectively, and the total body clearances were 0.65 ± 0.04 and 0.42 ± 0.05 L/kg h, respectively. The elimination half-lives of ampicillin after intravenous and intramuscular administration were 0.64 ± 0.11 and 0.63 ± 0.16 h, respectively, whereas for sulbactam the half-lives were 0.74 ± 0.12 and 0.77 ± 0.17 h, respectively. The bioavailability after intramuscular injection was high and similar in both drugs (73.34 ± 10.08% for ampicillin and 83.20 ± 7.41% for sulbactam). The mean peak plasma concentrations of ampicillin and sulbactam were reached at similar times (0.20 ± 0.09 and 0.34 ± 0.15 h, respectively) and peak concentrations were also similar but nonproportional to the dose of both products administered (13.07 ± 3.64 mg/L of ampicillin and 8.42 ± 1.74 mg/L of sulbactam). Both drugs had similar pharmacokinetic behaviour after intramuscular administration in rabbits.