Multicenter, comparative study of cycle control, efficacy and tolerability of two low-dose oral contraceptives containing 20 microg ethinylestradiol/100 microg levonorgestrel and 20 microg ethinylestradiol/500 microg norethisterone.
A comparison of cycle control, efficacy and tolerability of two oral contraceptive preparations containing 20 microg ethinylestradiol combined with either 100 microg levonorgestrel (EE/LNG 20/100) or 500 microg norethisterone (EE/NET 20/500) was conducted. These results were compared to a standard reference preparation, containing 30 microg ethinylestradiol combined with 150 microg levonorgestrel (EE/LNG 30/150). Efficacy data from 8,544 treatment cycles were obtained from 767 women. Good cycle control and effective contraception was achieved with the two LNG preparations, however, the cycle control results were less favorable with EE/NET 20/500. The cumulative incidence of women with at least one episode of intermenstrual bleeding from cycles 2 to 7 (primary target variable) was 43.9% for EE/LNG 20/100, 72.7% for EE/NET 20/500, and 15.7% for the standard EE/LNG 30/150. The difference between the 2 20 microg of EE preparations, which favored EE/LNG 20/100, was statistically significant (p = 0.001). The overall spotting rates (cycles 1-13) were 9.3% for EE/LNG 20/100, 21.7% for EE/NET 20/500, and 3.3% for the standard EE/LNG 30/150. Amenorrhea was reported in 7.1% (EE/LNG 20/100), 20.6% (EE/NET 20/500), and 0.9% (standard EE/LNG 30/150), respectively. Intermenstrual bleeding episodes were shorter with EE/LNG 20/100 and EE/LNG 30/150 of the 13 treatment cycles. The study Pearl indices were 0.9 for EE/LNG 20/100, 1.9 for EE/NET 20/500, and 0.0 for EE/LNG 30/150. All three treatments were well tolerated. However, tolerability was somewhat less favorable with EE/NET 20/500. A total of 160 women prematurely discontinued the study for various reasons (EE/LNG 20/100: 7%; EE/NET 20/500: 18%; EE/LNG 30/150: 4%). The overall adverse event incidence rate during the trial was low in all groups. Blood pressure remained largely unaffected. Thirteen serious adverse events were recorded for all treatment groups, all but one were assessed as not related to the treatments. There were no remarkable treatment related differences in mean body weight throughout the study and the laboratory values were largely unaffected in all three treatments groups.