Pharmacokinetics of piperacillin during pregnancy.

The pharmacokinetics of piperacillin during pregnancy were investigated. Eight pregnant women received 4 g of piperacillin intravenously before caesarean section. Likewise, five non-pregnant subjects of child bearing age received the same dose before a gynaecological operation. The mean peak plasma concentrations of piperacillin were 87.5 and 172.2 mg/L for the pregnant and non-pregnant patients, respectively. The mean umbilical vein concentration was 9.7 mg/L; the mean umbilical artery concentration was 7.4 mg/L and the amniotic fluid concentration 6.8 mg/L. The feto-maternal ratio at the time of caesarean section was 0.27. Pharmacokinetic parameters of piperacillin indicate larger volumes of distribution and higher clearance rates during pregnancy compared with the non-pregnant state. The altered pharmacokinetics of piperacillin during pregnancy suggest that higher doses may be required for effective treatment of serious infections in pregnant women near term.