Haemostatic effects of a new combined oral contraceptive, nomegestrol acetate/17β-estradiol, compared with those of levonorgestrel/ethinyl estradiol. A double-blind, randomised study.

Use of oral contraceptives (OC) that combine a progestogen with synthetic ethinyl estradiol (EE) is associated with increased risk of venous thromboembolism. NOMAC/E2 is a new monophasic OC that combines nomegestrol acetate (NOMAC), a highly selective progestogen, with 17β-estradiol (E2). The study objective was to compare the effects on markers of haemostasis of NOMAC/E2 (2.5 mg/1.5 mg) versus the second-generation OC, levonorgestrel (LNG)/EE (100 μg/20 μg). Healthy women (age 18-38 years) received once-daily treatment for three consecutive 28-day cycles in a double-blind, randomised study: either NOMAC/E2 for 24 days with a four-day placebo interval (n=45) or LNG/EE for 21 days with a seven-day placebo interval (n=45) per cycle. Mean changes from baseline to end-of-treatment in coagulation markers, including prothrombin fragment 1+2 (primary endpoint), fibrinolysis markers and platelet functions were assessed. Mean prothrombin fragment 1+2 levels (primary endpoint) did not increase with NOMAC/E2 compared with LNG/EE ( -0.02 vs. +0.08 nM, p<0.01). Other significant differences between NOMAC/E2 and LNG/EE were mean changes in antithrombin (+0.3% vs. -4.4%, p<0.001), activated protein C resistance - normalised ratio (+0.20 vs. +0.46, p<0.01), D-dimer ( -53 vs. +43 ng/ml, p<0.001), plasminogen (+6% vs. +30%, p<0.0001) and plasminogen activator inhibitor-1 ( -3.1 vs. -8.0 ng/ml, p<0.001). There was no effect of either treatment on platelet aggregation. The NOMAC/E2 pill regimen has fewer adverse effects on blood biological coagulation and fibrinolysis markers than LNG/EE. This suggests that NOMAC/E2 could have a more favourable venous thromboembolism risk profile than LNG/EE; further epidemiological data are required to confirm this.