Preliminary report on the treatment of endometriosis with low-dose mifepristone (RU 486)

Abstract

Objective: We have previously shown that treatment with mifepristone, 50 to 100 mg daily, results in amenorrhea, anovulation, and symptomatic improvement in women with endometriosis. In this study we lowered the dose to 5 mg daily to determine whether clinical efficacy is altered without other adverse actions.

Study design: After a baseline cycle, seven women with endometriosis were given mifepristone, 5 mg daily, for 6 months. Daily symptom inventories were recorded. Laparoscopy was performed during the sixth month of therapy.

Results: Pelvic pain improved in six of seven patients. Cyclic bleeding ceased in all patients, but four of the seven patients complained of irregular bleeding. Surgical staging at the conclusion of the study (five of seven patients) did not detect a change in endometriosis.

Conclusions: Mifepristone, 5 mg daily, resulted in symptomatic improvement, but did not stabilize the endometrium. From our experience with three doses of mifepristone, we would recommend a dose of 50 mg be used for continued investigations.

PIP: The authors' previous research has demonstrated that treatment with 50-100 mg/day of mifepristone produces symptomatic improvement of endometriosis. The present study assessed the efficacy of a substantially reduced antiprogesterone dose. After a baseline cycle, 7 US women with pelvic pain caused by endometriosis were administered 5 mg of mifepristone daily for 6 months. Clinical responsiveness was evaluated in daily symptom inventories completed by study participants. Pelvic pain improved significantly within 1 month of treatment initiation in 6 of 7 patients. Cyclic bleeding ceased in all 7 patients, but 4 women complained of irregular bleeding that begin 3-5 months into treatment. Menstrual cyclicity returned 23-37 days after study completion. 2 women did not complete the study--1 because of continued pelvic pain and 1 because of heavy bleeding during the fifth cycle. Surgical staging through laparoscopy in the 5 remaining women failed to document a significant change in endometriosis. 1 woman had a slight increase in endometriosis score compared to baseline, 1 had no change, and the remaining 3 women showed decreases from 32-45%. Given the failure of the 5 mg dose to stabilize the endometrium and the high rate of uterine bleeding, a dose of 50 mg of mifepristone is recommended for future investigations.