[Pharmacokinetics of metronidazole during perioperative short-term prophylaxis in cesarean section].

Placental transfer and elimination of metronidazole and its main metabolites, 1-(2-hydroxyethyl-)2-hydroxymethyl-5-nitroimidazole (metabolite I) and 2-methyl-5-nitroimidazole-1-acetic acid (metabolite II) were studied in newborn infants and compared with maternal data obtained in 8 high-risk parturients who were subjected to Caesarian section after intravenous infusion of 500 mg metronidazole. Unchanged metronidazole is rapidly transferred across the placental membranes. Its concentrations were the same in maternal venous blood and in both umbilical vessels at delivery. The concentrations of metabolite I were lower in the umbilical vein and artery than in the mother in the first hour after infusion. The elimination half-lives of metronidazole and metabolite I were markedly prolonged in the newborn infants in comparison with the maternal values. No adverse effects were observed in infants or mothers.