Bioavailability, disposition kinetics and renal clearance of ampicillin following three routes of administration in sheep.

Bioavailability, disposition kinetics and renal clearance of ampicillin were investigated in 8 sheep following intravenous (i.v.), or intramuscular (i.m.) injection of 10 mg/kg or oral administration of 20 mg/kg dose. Peak of absorption was achieved in 26 +/- 9 min (mean +/- SD) after i.m. and 85 +/- 24 min after oral administration. The relative bioavailability of i.m. injected drug was 95 +/- 20 per cent compared to only 37 +/- 7 per cent following oral administration of double the dose. The disposition kinetics parameters of ampicillin were comparable in sheep with all three routes of drug administration. The renal clearance of ampicillin varied between 0.20 and 0.62 ml/min.kg while total body clearance was 50 to 64 ml/min.kg. The fractional urinary excretion of ampicillin in the first 8 hours after dosing was less than 1 per cent of the dose by all three routes.