Induction of labor by oral PGE2 administration--evaluation of different dose schedules

The efficacy and safety of different oral doses of PGE2 in tablet form were evaluated in 30 women admitted to the hospital for labor induction at or near term. The aim was to select a recommendable dose schedule based on recording of uterine contractility, clinical outcome and measurement of the resulting plasma levels of the two prostaglandin metabolites 15-keto-13, 14-dihydro-PGE2 and 15-keto-13, 14-dihydro-PGE2 alpha by gas-chromatography-mass spectrometry and by radio-immunoassay. Measurements of uterine contractility and of plasma levels of the PGE2 metabolite both showed that the preferable interval between oral doses of PGE2 tablets is one hour. Following 1.0 mg PGE2, the plasma concentration peaked after 45 to 60 minutes and had returned to approximately pretreatment levels after 120 minutes. With a two-hour interval between doses there was above all a decreased frequency of contractions in the last part of the interval. No such variation in the contractility pattern was seen when 1.0 mg PGE2 was administered every hour. When the individual dose was increased to 2.0 mg, signs of overstimulation of uterine contractility were observed. The plasma concentration of the E2 metabolite increased in accordance with the oral dose. A slow rise in the plasma concentrations of the E2 and F2 alpha metabolites was found some hours following initiation of treatment, possibly indicating an increased endogenous prostaglandin biosynthesis, probably secondary to the stimulated uterine contractility.