An RCT of varying oral contraceptive regimens in the treatment of primary dysmenorrhea

Abstract

Primary dysmenorrhea (PD) is the most common cause of pelvic pain in women. Oral contraceptives (OCP) are frequently prescribed, but not always effective. We theorized that cyclic OCP which induces withdrawal bleeding allows the production of prostaglandins and persistent pain. Continuous OCP (COCP) has not been studied as a primary treatment of PD, although recent studies show its superiority to traditional regimens in the treatment of endometriosis. We hypothesized that continuous OCP will result in more pain relief than cyclic administration in PD patients. A double-blind, randomized controlled trial (RCT) comparing COCP to a cyclic 21/7 regimen for 6 months in PD patients. We conducted a trial of two treatment regimens of a monophasic OCP (gestodene 0.075 mg/ethinyl estradiol 20 mcg) in 38 PD patients. The primary outcome was the difference in subjective perception of pain as measured by the Visual Analog Scale (VAS) over the period of six months, as analyzed by a mixed-effects model to account for the within-subject correlation over time. 33 patients completed the study. Mean VAS score (SD) in the cyclic regimen was 64.4 (31.9) at screening visit, 19.0 (24.8) after one month, and 5.2. (9.5) at the end of the study. Mean VAS score in the COCP group was 75.6 (16.7) at screening visit, 3.1 (5.8) after one month, and 0.8 (1.4) at the end of the study. In both groups pain reduction measured by VAS was significant compared to baseline. COCP regimen was superior to cyclic regimen when comparing pain reduction after one (mean difference: -27.3; 95% CI: (-40.5,-14.2); P<0.001) and three (mean difference: -17.8; 95% CI: (-33.4,-2.1); P=0.03) months of treatment, and almost reached statistical significance after six (mean difference: -16.0; 95% CI: (-32.2,0.1); P=0.05) months of treatment. Although both regimens of OCP are efficient in the treatment of PD, COCP regimen is superior to cyclic OCP in the short term.