A randomised double-blind trial to determine the bleeding profile of the prolonged-release contraceptive dienogest 2 mg/ethinylestradiol 0.02 mg versus an immediate-release formulation of drospirenone 3 mg/ethinylestradiol 0.02 mg.

Background: Dienogest (DNG) 2 mg/ethinylestradiol (EE) 0.02 mg is the first low-dose combined oral contraceptive (COC) with a prolonged-release formulation that allows stable plasma concentrations and has high contraceptive efficacy (Pearl index: 0.2). The aim of this trial was to determine the bleeding profile of this contraceptive compared to an immediate release formulation.

Methods: This prospective double-blind randomised controlled trial evaluated the bleeding patterns of DNG 2 mg/EE 0.02 mg compared with immediate-release drospirenone (DRSP) 3 mg/EE 0.02 mg in a 24/4-day regimen over nine cycles (randomisation ratio, 5:2). Participants recorded scheduled and unscheduled bleeding/spotting data using an electronic diary. A non-inferiority analysis for the proportion of participants with unscheduled bleeding/spotting was prespecified for Cycles 2-6. Safety, including adverse events, were monitored throughout the trial.

Results: Seven-hundred six and 288 participants received DNG/EE and DRSP/EE, respectively. Scheduled bleeding patterns per each 28-day cycle were similar in both groups. During Cycles 2-6, the proportion of participants with unscheduled bleeding/spotting was significantly lower in the DNG/EE group (50.5% [280/574] than in the DRSP/EE group (72.8% [171/235]]; treatment difference 22.3% [95% CI 15.9, 28.6%];  < 0.0001). A low proportion of participants discontinued the trial due to bleeding disorders (1.7% and 0.7%, respectively). The safety profiles were similar for both treatments.

Conclusions: The prolonged-release DNG 2 mg/EE 0.02 mg offers a significant decrease in unscheduled bleeding/spotting compared with an immediate-release COC, DRSP/EE, combined with high contraceptive efficacy and a very low adverse event profile.