Cycle Control With a 21-Day Compared With a 24-Day Oral Contraceptive Pill: A Randomized Controlled Trial

Abstract

OBJECTIVE:: To compare bleeding patterns between a 21/7-day triphasic norgestimate/ethinyl estradiol (E2) 25-microgram oral contraceptive pill (OCP) and a 24/4-day drospirenone/ethinyl E2 20-microgram OCP. METHODS:: In a three-cycle open-label multicenter study healthy sexually active women were assigned randomly to a 21/7-day (norgestimate/ethinyl E2) or 24/4-day (drospirenone/ethinyl E2) OCP regimen. Randomization was stratified to assure a balanced distribution between regimens for "fresh starts" and "switchers." Bleeding data were collected daily using an interactive voice-response system. Bleeding was defined according to the 2007 U.S. Food and Drug Administrations Reproductive Health Drug Advisory Committee-endorsed criteria. RESULTS:: Across the three cycles the 21/7-day OCP group (n=165) reported fewer unscheduled bleeding days than did the 24/4-day OCP group (n=167) (mean 4.6 compared with 6.1 days P=.003). Women using the 21/7-day OCP had significantly fewer episodes of unscheduled bleeding than did those using the 24/4-day OCP (mean 1.47 compared with 2.01 P=.001). Moreover women using the 21/7-day OCP had a significantly lower absence of scheduled bleeding at each cycle (P<.001). Both regimens were well-tolerated. CONCLUSION:: A 21-day norgestimate/ethinyl E2 25-microgram regimen results in less unscheduled bleeding and more scheduled bleeding than does a 24-day drospirenone/ethinyl E2 20-microgram regimen. CLINICAL TRIAL REGISTRATION:: ClinicalTrials.gov www.ClinicalTrials.gov NCT00745901. LEVEL OF EVIDENCE:: I.