Meperidine metabolism in the parturient

A study of meperidine metabolism was undertaken in 21 normal parturients at term. Meperidine, 50 mg intravenously, was the sole analgesic agent used during the intrapartum period. Maternal and cord blood assessment for meperidine and normeperidine was done by gas chromatography-mass spectrophotometry. Most maternal sera showed a typical meperidine elimination curve. A secondary rise in maternal meperidine 30 to 180 minutes after injection was found in 4 patients. One patient showed a significant alteration in normeperidine appearance. These data add further validity to the hypothesis that the pregnant woman can metabolize meperidine by several pathways.