Efficacy and safety of a new 24-day oral contraceptive regimen of norethindrone acetate 1 mg/ethinyl estradiol 20 μg (Loestrin® 24 Fe)

Abstract

Background New low-dose formulations of combination oral contraceptives (COCs) are safe and effective, but they may be associated with an increased risk of breakthrough bleeding. Extending the duration of active hormonal treatment may reduce the frequency of intracyclic bleeding/spotting while maintaining efficacy and tolerability. Methods This 6-month, open-label, randomized, active-controlled study involved healthy women aged 18–45 years who were at risk for pregnancy. Women were randomized 4:1 to a 24-day regimen of norethindrone acetate 1 mg/ethinyl estradiol 20 μg (NETA/EE-24) or to a 21-day regimen of the same combination (NETA/EE-21). The outcomes assessed included pregnancy and incidence, duration of bleeding and intensity of bleeding. Results The cumulative risk of pregnancy in the NETA/EE-24 group ( n=705) was 0.9% during six cycles of treatment. Compared with NETA/EE-21 ( n=181), NETA/EE-24 was associated with significantly fewer intracyclic bleeding days (0.95 vs. 1.63; p=.005), fewer days of withdrawal bleeding (2.66 vs. 3.88; p<.001) and fewer total bleeding/spotting days for Cycles 2–6 (18.6 vs. 23.2; p<.001). NETA/EE-24 was well tolerated, and side effects were generally mild to moderate in severity. Conclusions NETA/EE-24 is an effective well-tolerated COC that is associated with a bleeding profile more favorable than that of NETA/EE-21.