Different Dosages of Mifepristone Versus Enantone to Treat Uterine Fibroids: A Multicenter Randomized Controlled Trial

Background: To evaluate the efficacy and safety of 10 mg and 25 mg mifepristone per day compared with 3.75 mg enantone in treating uterine fibroids.

Methods: This is a Multicenter randomized controlled trial. A total of 501 subjects with symptomatic uterine fibroids were enrolled and randomized into the group of 10mg, 25mg mifepristone and 3.75 enantone (with 307, 102 and 92 subjects respectively), with 458 subjects completed the treatment. Three months of daily therapy with oral mifepristone (at a dose of either 10 mg or 25 mg) or once-monthly subcutaneous injections of enantone (at a dose of 3.75 mg) were used. Change in volume of the largest uterine fibroid was the primary efficacy variable, and secondary efficacy variables included changes in anemia and relevant symptom. Safety evaluation included the analyses of adverse events, laboratory values, and relevant endometrial changes.

Results: After three months of treatment, the mean volume of the largest leiomyoma was significantly reduced by mifepristone 10 mg or 25 mg or enantone 3.75 mg (40.27%, 42.59% and 44.49% respectively) (P < 0.0001). Percentage change from baseline in largest leiomyoma volume was not statistically significant among the three groups (P = 0.1057). Most of the patients in all groups experienced amenorrhea after the treatment. There were also significant elevations in red blood cell count, hemoglobin and hematocrit (P < 0.0001), and significant reductions in prevalence of dysmenorrhea, pelvic pressure, non-menstrual abdominal pain (P < 0.0001) in each group, while no significant difference among the three groups.All study medications are well-tolerated, and no serious adverse event was reported. Treatment-related adverse event rate was significantly lower in mifepristone 10 mg group, compared to Enantone 3.75 mg group (13.59% vs. 32.58%, P = 0.0002). In both mifepristone groups, estradiol levels were maintained in the premenopausal range, whereas patients in the enantone group had a significant reduction to postmenopausal levels (P < 0.0001).

Conclusion: 10mg is as effective as 25mg mifepristone and 3.75 mg enantone with minimal drug-related side effects, and may provide an alternative for clinical application, especially for patient who are in perimenopause with uterine fibroids.