Abortion of Early Pregnancy on an Outpatient Basis Using Silastic 15(S)-15-Methyl Prostaglandin F2α Vaginal Devices *

Hormonal changes associated with the use of 15(S)-15-methyl prostaglandin F 2 α in a Silastic device as an abortifacient were evaluated during very early first-trimester pregnancy. Five of six patients aborted completely with drug alone. Measurement of plasma samples demonstrated rapid drug absorption with apparent effective concentrations of 600 to 3000 pg/ml but without a pattern of sustained release and absorption. Routine serial determination of both serum chorionic gonadotropin (hCG) and β -subunit hCG were used to assess the efficacy of treatment. Although more sensitive, β -hCG measurement offered no advantage clinically over the standard hCG assay. Plasma progesterone values also reflected success or failure of the technique. Vomiting and diarrhea continue to be problems associated with the use of these compounds. The Silastic device may be the forerunner of a self-administered early abortifacient. Continued efforts are necessary to elucidate mechanisms of action and to find an analog specific for myometrial stimulation.