Effect of prostaglandin E2 and its metabolites on lower segment myometrium in vitro.

The spontaneous activity of pregnant human lower segment myometrium has been studied in vitro using strips removed at cesarean section. Contractions were measured isometrically. During the 4-h experiments there was in increase in amplitude and decrease in frequency of contractions in control preparations. Prostaglandin F2 alpha (PGF2 alpha), its metabolites and prostaglandin E2 (PGE2) have been shown to be oxytocic in vivo, but there are no published data on the oxytocic effect of PGE2 metabolites. The effect on contractile activity of adding either PGE2 or one of its initial metabolites (15-keto-PGE2, 13,14-dihydro-15-keto-PGE2 or 13,14-dihydro-PGE2) or prostaglandin A2 (PGA2) to the tissue baths has been tested. No significant or consistent change in contractility was observed after the addition of any of the compounds tested. This probably indicates an inherent difference in the response of different portions of the uterine muscle, and cannot be taken to exclude activity in the intact uterus, particularly since PGE2 is a well-known oxytocic agent in vivo. The difficulty of working with this type of preparation is stressed, since there is wide variation in contractility as well as a constantly changing pattern.

The systemic absorption from the vagina of prostaglandin E2 administered for the induction of labour.

The absorption rates of PGE2 released from tablets, gel and pessary bases inserted into the vagina for the induction of labour in a total of 27 patients have been measured by means of serial plasma 15-keto-PGE2 levels. The results are discussed with a view to obtaining both the optimum dose of PGE2 and vehicle of release.

The routine use of oral prostaglandin E2 tablets for induction or augmentation of labour.

The use of oral prostaglandin E2 (PGE2) tablets is an effective and safe adjunct to low amniotomy for the induction of labour at term. Routine use of this regimen and the use of oral PGE2 tablets for augmentation of spontaneous labour has shown that the method is very effective in multiparous patients, but much less so in primiparous patients. Success or failure could not be predicted by the pre-induction Bishop score. The incidence of gastro-intestinal side effect is dose dependent, but is low in multiparous patients.

Prostaglandin E2 tablets used intravaginally for the induction of labour.

Prostaglandin E2 tablets were administered intravaginally 505 patients for the induction of labour, without amniotomy, using doses ranging from 1 to 5 mg as a single insertion. The advantages and limitations of this method of induction of labour are discussed.

PIP: Prostaglandin E2 (PGE2) tablets were administered intravaginally to 505 patients for labor induction, without amniotomy, in doses ranging from 1-5 mg as a single insertion in this randomized, double-blind study conducted at 2 hospitals. Patient mean age, pregnancy duration, and pretreatment Bishop score did not differ significantly among the groups of patients receiving various doses of PGE2. The preinduction Bishop score and percentage of patients successfully induced with 3-mg intravaginal PGE2 tablets were significantly greater, whereas the induction-delivery time was significantly shorter, in patients delivered at Whipps Cross Hospita vs. Charing Cross Hospital (P .05). Plasma levels of 15-keto-PGE2 after the 3-mg dose of PGE2 in 4 selected patients showed wide variation. Labor was not induced in 1 patient with intermittent low plasma 15-keto-PGE2 levels, but it was successfully induced in the other 3, although the patient with the highest plasma level did not become established in labor until the end of the sampling period. Other unpublished studies showed no detectable levels of endogenous 15-keto-PGE2 in patients in spontaneous labor, and so these measurements illustrated the wide variation in plasma levels of 14-keto-PGE2 after a single intravaginal cose. No instances of gastrointestinal side effects or uterine hypertonus were recorded. An increase by 1-mg increments up to 5 mg did not increase the success rate. The effectiveness of this method of labor induction was greater than that of oxytocin without amniotomy and comparable with that achieved using extra-amniotic PGE2, and it is simpler than these 2 methods.

Radioimmunoassay of 15-keto-prostaglandin E2 in peripheral plasma after oral administration of prostaglandin E2 tablets used for induction of labour.

A radioimmunoassay of the 15-keto- metabolite of prostaglandin E2 has been developed. The details of the assay are described. Using unextracted plasma, serial measurements of 15-keto-PGE2 have been carried out every 15 minutes for 3 hours in 9 women ingesting 0.5 mg PGE2 oral tablets used for the induction of labour.