Metabolic and quantitative studies in connection with intraamniotic administration of prostaglandin F2α for induction of therapeutic abortion

Prostaglandin F2α, unlabeled or tritium-labeled, was administered intraamniotically to eight women in the second trimester of pregnancy. The absorption of PGF2α from amniotic fluid and the metabolism of the compound were studied in samples of blood, amniotic fluid, and urine. The radioactivity in amniotic fluid was found to disappear very slowly, and 5 to 10 hrs after the administration several other radioactive compounds appeared in the amniotic fluid. The main product was identified as 9α, 11α-dihydroxy-15- -ketoprost-5-enoic acid by gas chromatography-mass spectrometry of two derivatives. The metabolites excreted into urine were found to be identical with those obtained after intravenous injection of PGF2α. Low concentrations of PGF2α, around 0.2–0.3 nanog/ml, were found in plasma following intraamniotic administration. The metabolite was found in much higher concentrations; the maximum levels ranged between 1.5 and 14.8 nanog/ml.