Low-dose oral contraceptive pill for dysmenorrhea associated with endometriosis: a placebo-controlled, double-blind, randomized trial

ObjectiveTo evaluate the efficacy of a low-dose oral contraceptive pill (OCP) for patients with dysmenorrhea associated with endometriosis.DesignA double-blind, randomized, placebo-controlled trial.SettingsClinical trial sites in Japan.Patient(s)One hundred patients with dysmenorrhea associated with endometriosis. Most enrolled patients had radiologic evidence of endometriosis rather than surgical diagnosis.Intervention(s)Patients were randomly assigned to receive either monophasic OCP (ethinylestradiol plus norethisterone) or placebo. Participants used their usual pain medications as needed during the trial.Main Outcome Measure(s)After four cyclic treatments, we used a zero- to three-point verbal rating scale and a visual analogue scale to measure the severity of disability because of dysmenorrhea in daily life, and the patients' use of analgesics.Result(s)Total dysmenorrhea scores assessed by the verbal rating scale were significantly decreased at the end of treatment in both groups. From the first cycle through the end of treatment, dysmenorrhea in the OCP group was significantly milder than in the placebo group. Nonmenstrual pelvic pain was present at baseline in 24.5% (12 of 49) of the OCP group and 34.0% (16 of 47) of the placebo group. The volume of endometrioma (larger than 3 cm in diameter) was significantly decreased in the OCP group, but not in the placebo group. No serious adverse events related to using OCPs occurred.Conclusion(s)The present study clearly demonstrated for the first time that OCPs could be used to effectively and safely treat pain associated with endometriosis.