SummaryThe pharmacokinetics of a single dose of intravenous ampicillin were studied in nine patients during their third trimester of pregnancy. Each volunteer was given either 500 mg (5.7–8.8 mg/kg) or 1 g (15.4–21.4 mg/kg) of sodium ampicillin by rapid infusion. Postinfusion plasma concentration—time curves followed biexponential decay in all subjects. Calculated parameters included a mean plasma distribution volume of 177.1 ± 97.5 ml/kg, tissue or peripheral distribution volume of 246.2 ± 143.9 ml/kg, elimination half-life of 1.60 ± 0.51 h, and total body clearance of 4.59 ± 1.48 ml/min/kg. Dose-dependent disposition was not observed. Gestation-specific drug therapy research during pregnancy is discussed.