Hormone Choice Can Affect Bleeding Patterns in Continuous OC

A growing number of physicians and patients are looking to continuous use of oral contraceptives (OCs) to reduce the number of menstrual days and provide other quality-of-life improvements. But there are unanswered questions about the effect of different hormones used in OC on bleeding patterns.

A study from Oregon Health Sciences University in Portland, OR, concluded that norethindrone acetate (NET) may be a preferred agent. Use of a continuous OC with NET results in more days of amenorrhea and fewer days of bleeding than preparations containing levonorgestrel (LNG).

A group led by Stephanie Koontz, MD, compared 100 mcg LNG with 1 mg NET in a randomized, double-blind active treatment trial with 139 women for 6 months. Both agents were used with additions of ethinyl estradiol (EE) in 20- and 30-mcg doses. Women in the study logged bleeding and other adverse effects on a daily menstrual calendar. An exit survey was used to measure overall satisfaction with treatment.

There were dropouts in all four groups, but significantly more women in the NET group completed the trial compared to the LNG group. Women taking NET plus EE 30 mcg were most successful, with 72% completing the trial. That compares to 55% for NET plus EE 20 mcg, 44% for LNG plus EE 30 mcg, and 56% for LNG plus EE 20 mcg.

The LNG + EE 30 mcg group reported the lowest percentage of total days of amenorrhea (75%), similar to the LNG + EE 20 mcg group at 80%. Both LNG groups reported significantly more days of amenorrhea than NET + EE 20 mcg (89%) and NET + EE 30 mcg (87%). There were no significant differences in adverse events, but women on LNG + EE 30 mcg were less satisfied than women in the other three groups.

Koontz SL, Edelman AB, Nichols MD, Jensen JT. Continuous oral contraceptives: Are bleeding patterns dependent on the hormones given? Obstet Gynecol. 2005;105(4 suppl):55S.