Time-related effects of RU486 treatment in experimentally induced endometriosis in the rat

OBJECTIVE: To evaluate the time-dependent effect of the progesterone antagonist RU486 on experimentally induced endometriosis in the rat. DESIGN: Endometriosis was induced by implanting endometrium onto the peritoneal side wall. Size of the implants was measured before and after treatment. PARTICIPANTS: Fifty-two adult female Sprague-Dawley female rats weighing 200 to 225 g. SETTING: Departmental research laboratory of university hospital. INTERVENTION: Animals treated with RU486 or vehicle only for 2, 4, 6, or 8 weeks. MAIN OUTCOME MEASURES: Size of the implant was measured before and after treatment; relative change in size of the implants was calculated. RESULTS: There was not a statistically significant difference between the treatment groups and the control groups. There was no regression of endometriosis in any of the treatment groups. CONCLUSIONS: RU486 administered for 8 weeks in the rat model was not effective therapy for endometriosis.