Cycle control with oral contraceptives containing 20 micrograms of ethinyl estradiol. A multicenter, randomized comparison of levonorgestrel/ethinyl estradiol (100 micrograms/20 micrograms) and norethindrone/ethinyl estradiol (1000 micrograms/20 micrograms).

A randomized, open-label, multicenter study was undertaken to compare the effects of oral contraceptives (OC) containing 100 micrograms levonorgestrel (LNG)/20 micrograms ethinyl estradiol (EE) (Aless/Loette) and 1000 micrograms norethindrone acetate (NETA)/20 micrograms EE (Loestrin Fe 1/20) on menstrual cycle control over four cycles of use. A total of 84 evaluable women provided 274 cycles of exposure in the LNG/EE group, and 89 women provided 289 cycles of exposure in the NETA/EE group. Overall, the LNG/EE group achieved a consistently higher percentage of normal menstrual cycles as well as a lower rate of intermenstrual bleeding and amenorrhea than the NETA/EE group. In cycle 4, 63.8% of cycles were normal in the LNG/EE group compared with 41.9% in the NETA/EE group (p < 0.005). Of the total cycles in the NETA/EE group, 10% were amenorrheic, compared with 1.1% in the LNG/EE group. The occurrence of bleeding and/or spotting was significantly lower in cycles 2 and 3 in the LNG/EE group (41.7% and 34.8%, respectively) compared with the NETA/EE group (62.3% and 56.3%; p < 0.05). Other cycle variables were generally similar between groups, as was the incidence of adverse events. These results demonstrate that good cycle control was achieved with an OC containing 20 micrograms EE and that 100 micrograms LNG/20 micrograms EE produces better cycle control than 1000 micrograms NETA/20 micrograms EE.