Effects of Dienogest on Surgically Induced Endometriosis in Rats after Repeated Oral Administration

Background: Dienogest demonstrates efficacy for lesion reduction and pain relief in clinical trials of endometriosis. The current study investigated an intraperitoneal animal model of endometriosis to further characterize the effects of dienogest. Methods: Endometrial-like lesions were induced in rats by autotransplantation of uterine tissue into the peritoneal cavity. Dienogest 0.3 or 1.0 mg/kg/day, danazol 100 mg/kg/day, or vehicle control were administered orally for 28 days. Changes in endometrial-like lesion size during treatment were assessed at laparotomy. Uterine horn weight was also measured as an index of the estrogenic effects of treatment. Results: Dienogest 0.3 mg/kg/day significantly reduced the total endometrial lesion area, with an effect equivalent to danazol 100 mg/kg/day. Unlike dienogest 1.0 mg/kg/day, dienogest 0.3 mg/kg/day had no effect on uterine horn weight, indicating an absence of estrogenic effects for this dose in rodents. Conclusion: Dienogest 0.3 mg/kg/day for 28 days demonstrated potent inhibitory activity on the growth of endometrial tissue in this model, providing supportive evidence for the efficacy of dienogest in lesion reduction. Copyright (C) 2011 S. Karger AG, Basel