Prostaglandin metabolite levels during cervical ripening with a controlled-release hydrogel polymer prostaglandin E2 pessary.

Prostaglandin E and F metabolite (PGEM and PGFM) concentrations in peripheral plasma were assayed following the vaginal administration of a controlled release hydrogel polymer pessary designed to release 0.6 mg PGE2 per hour in vivo. A linear relationship between calculated PGE2 release from the pessary and PGEM levels was observed with a correlation coefficient of 0.78. A significant rise in PGEM levels occurred two hours following pessary administration, with significantly higher PGEM levels in patients delivering within the eight hour observation period compared with those delivering later. PGFM levels increased more slowly. The results suggest that PGE2 released by the pessary crosses the vaginal epithelium and may stimulate endogenous prostaglandin production. The controlled rise of metabolites in association with the polymer pessary suggest that it should provide greater control in labour induction than other vehicles we have studied, but this should be confirmed by clinical trials.