VAGINAL ADMINISTRATION OF PGE(2) FOR INDUCTION OF LABOR STIMULATES ENDOGENOUS PGF(2 alpha) PRODUCTION

Prostaglandin E, is effective for induction of labor but many preparations exist using a variety of vehicles from which the active ingredient may not be equally available. Plasma concentrations of bicyclic PGE(2) metabolite (PGEM) and 13, 14-dihydro, 15-keto PGF(2 alpha) (PGFM) were measured following administration of a 3mg PGE, vaginal tablet or lmg PGE(2) vaginal gel to twenty-four parous women with favorable induction features, randomly allocated to receive one or other preparation. PGEM increased rapidly following both administration of the 3mg PGE(2) vaginal tablet and the lmg PGE(2) vaginal gel, reaching a peak within 40 minutes of PGE(2) administration. The maximal rise in PGEM in the gel group correlated directly with the change in cervical score and inversely with the need for augmentation with oxytocin and the induction-delivery interval. A secondary rise in PGFM was noted in both groups 3-4 hours following PGE, administration. The magnitude of the increase in PGE, may be important in the clinical response to PGE(2) administration, while PGE, absorption may switch-on endogenous PGF(2 alpha) production, similar to what is seen in spontaneous labor.