OBJECTIVE: To compare bleeding patterns between a 21/7-day triphasic norgestimate/ethinyl estradiol (E2) 25microgram 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

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... arts" 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 Administration's Reproductive Health Drug Advisory Committee-endorsed criteria. RESULTS: Across the three cycles, the 21/7-day OCP group (n‫)561؍‬ reported fewer unscheduled bleeding days than did the 24/4-day OCP group (n‫)761؍‬ (mean 4.6 compared with 6.1 days, P‫.)300.؍‬ 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.)100.؍‬ 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 25microgram 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.