Dr. Barbieri responds
I thank Drs. Chow, Barnes, and Ribot for their interest in my recent editorial on the medical treatment of endometriosis. I agree with Dr. Chow that dienogest, a synthetic progestin, is effective in the treatment of pelvic pain caused by endometriosis. In one observational study, norethindrone acetate 2.5 mg daily and dienogest 2 mg daily had similar efficacy in the treatment of pelvic pain. Dienogest treatment was associated with fewer side effects but was much more expensive than norethindrone acetate.1 The US Food and Drug Administration has approved a combination estradiol- progestin pill (Natazia, Qlaira) as a contraceptive, and I have occasionally used this medication in my practice for women with pelvic pain caused by endometriosis. Dienogest monotherapy is not available in the United States.
Dr. Barnes reminds us that norethindrone is a substrate for the aromatase enzyme system and can be converted to ethinyl estradiol.2 The conversion occurs at a very low rate, likely less than 0.4%.3 At a norethindrone acetate dose of 5 mg daily, aromatization would result in the production of less than 2 μg of ethinyl estradiol daily.
Dr. Ribot advocates for surgery as the primary treatment of pelvic pain caused by endometriosis. I agree with Dr. Ribot that, for severe pain caused by deep infiltrating endometriosis, surgery is an optimal approach. However, for women with pelvic pain and Stage I endometriosis, hormonal treatment after initial surgical diagnosis and treatment reduces pain recurrence and repetitive surgical procedures.4
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