Long-term use of dienogest for the treatment of endometriosis

Aim: To investigate the safety and efficacy of 52 weeks of dienogest treatment in patients with endometriosis. Methods: One hundred and thirty‐five patients with endometriosis received 2 mg of dienogest orally each day for 52 weeks. Adverse drug reactions and bone density were evaluated. Global improvement was assessed based on the changes in severity categories of five subjective symptoms during non‐menstruation (lower abdominal pain, lumbago, dyschezia, dyspareunia, and pain on vaginal examination) and two objective findings (induration involving the pouch of Douglas and limited uterine mobility). Results: The most common adverse drug reactions included metrorrhagia (71.9%), headaches (18.5%), and constipation (10.4%). No clinically significant changes were noted in the incidence or severity of reactions associated with the course of the treatment period (52 weeks). Changes from the baseline bone mineral density of the lumbar spine measured by dual‐energy X‐ray absorptiometry were −1.6 ± 2.4% and −1.7 ± 2.2% (mean ± standard deviation) at 24 and 52 weeks, respectively, which were statistically significant decreases; however, there was no cumulative decrease. The proportions of patients assessed as marked or moderate improvement in terms of global improvement were 72.5% (95/131 cases) at 24 weeks and 90.6% (106/117 cases) at 52 weeks. Conclusion: The long‐term effect of dienogest on bone mineral density was slight, whereas the efficacy increased cumulatively.