Early First-Trimester Abortion Induction by Silastic Vaginal Devices for Continuous Release of 15(S)-15-Methyl Prostaglandin F2α Methyl Ester

Abstract

The abortifacient efficacy of four Silastic devices containing 15(S)-15-methyl prostaglandin F2alpha methyl ester (15-Me-PGF2alpha methyl ester) was evaluated by single vaginal insertion and retention for 24 hours in four groups of ten patients each at 31 to 49 days beyond the 1st day of the last menstrual period. There were eight complete and two incomplete abortions in the group receiving a device with a drug concentration of 0.5% and a surface area of 20 sq cm. Four complete abortions, four incomplete abortions, and two failures occurred with a 0.2%, 10 sq cm device. Seven complete and two incomplete abortions were obtained with a 0.5%, 10 dq cm device; one patient in this group was found to have aborted prior to treatment. A 0.5%, 2o sq cm device with one-half the thickness of the other 0.5% devices yielded five complete abortions, one incomplete abortion, and four failures. Side effects were minor and well tolerated in each group. Serial determinations of plasma progesterone, human chorionic gonadotropin, and 15-Me-PGF2alpha were obtained and related to the outcome of therapy. Because of failure to achieve sustained blood levels of drug or satisfactory rates of complete abortions, this technique, with the devices used in this study, is not believed to be acceptable for routine early first-trimester pregnancy termination.