Pooled analysis of two randomized, open-label studies comparing the effects of nomegestrol acetate/17β-estradiol and drospirenone/ethinyl estradiol on bleeding patterns in healthy women.

Objectives: To obtain more precise and detailed information regarding the bleeding patterns of nomegestrol acetate (NOMAC)/17β-estradiol (E2) and drospirenone/ethinyl estradiol (DRSP/EE) and to identify whether baseline demographic characteristics were associated with unscheduled bleeding, absent scheduled bleeding, or amenorrhea.

Study Design: This analysis pooled results from two pivotal open-label, randomized trials that compared bleeding patterns of NOMAC/E2 and DRSP/EE. In the two studies 4317 women aged 18-50 years from 24 countries across the Americas, Europe, and Asia underwent treatment.

Results: 2835 women taking NOMAC/E2 (2.5 mg/1.5 mg) in a 24/4-day regimen and 938 women taking DRSP/EE (3 mg/30 μg) in a 21/7-day regimen had at least 1 evaluable cycle for vaginal bleeding analyses. The frequency of absent scheduled bleeding was higher (p<.0001) for women using NOMAC/E2 than DRSP/EE across all 11 cycles (cycles 2-12), ranging between 17.6% and 31.6% and between 3.4% and 5.8%, respectively. For women who had absent scheduled bleeding in cycles 2, 3, or 4 the incidence of absent scheduled bleeding in subsequent cycles was high and ranged between approximately 50%-60% for NOMAC/E2 and approximately 40%-50% for DRSP/EE. Amenorrhea increased over time with both regimens, being higher with NOMAC/E2. Both absent scheduled bleeding and amenorrhea with NOMAC/E2 were more common in older women, overweight women, switchers, and smokers; unscheduled bleeding was more common in starters, but had no association with age, body mass index, and smoking.

Conclusions: NOMAC/E2 is associated with a higher prevalence of absent scheduled bleeding compared with DRSP/EE. Absent scheduled bleeding and amenorrhea were associated with age, body weight, switching and smoking. Unscheduled bleeding was more common in starters.

Implications: Information about the factors associated with bleeding patterns may help clinicians provide guidance to women considering use of the NOMAC/E2 oral contraceptive.