Continuous oral contraceptives: are bleeding patterns dependent on the hormones given?

To estimate whether progestin type or estrogen dose influences bleeding patterns, adverse effects, or satisfaction with combined oral contraceptives dosed continuously.

This was a randomized, double blind, 4-arm active treatment study. Subjects received either 100 microg levonorgestrel/20 microg ethinyl estradiol (E2) (20LNG group), 100 microg levonorgestrel/30 microg ethinyl E2 (30LNG group), 1,000 microg norethindrone acetate/20 microg ethinyl E2 (20NETA group), or 1,000 microg norethindrone acetate/30 microg ethinyl E2 (30NETA group) for 180 days. Subjects logged bleeding events and adverse effects on a daily menstrual calendar. An exit survey measured satisfaction with bleeding patterns.

One hundred thirty-nine women were enrolled. Patients in the 20NETA and 30NETA arms had significantly more days of amenorrhea than the 30LNG arm in the second 90 days (P < .008). The 30LNG group reported more spotting days than the 20NETA group over the entire study period (P < .008) and the 30NETA group for the second 90 days (P < .008). Only a small number of bleeding days were reported with no differences between groups. No differences in adverse effects between groups were found. Women in the 30LNG arm reported lower levels of satisfaction with their bleeding patterns than the other groups (30LNG compared with 20NETA, P = .01; 30LNG compared with 30NETA, P = .001).

The addition of 10 microg of ethinyl E2 to a 20 microg ethinyl E2 pill containing levonorgestrel or norethindrone acetate did not improve bleeding patterns. During continuous dosing, the use of oral contraceptives containing 1,000 microg norethindrone acetate resulted in more days of amenorrhea and fewer days of spotting than preparations containing 100 microg levonorgestrel.

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