Abstract

Introduction: Contraceptives containing ethinylestradiol (EE) induce changes in the coagulation system and are associated with a risk of venous thromboembolism. However, studies comparing the effects of combined oral contraceptives containing EE and low-potency estrogens (ie, estradiol [E₂] and estradiol valerate [EV]) on coagulation biomarkers are limited. This study represents secondary outcomes of a randomized trial comparing combined oral contraceptives containing EV + dienogest (DNG), EE + DNG, and DNG alone on selected coagulation biomarkers. We could compare the specific effects of the different estrogen components owing to the inclusion of preparations containing the same progestin.

Material and methods: We enrolled 59 healthy, 18- to 35-year-old, non-smoking women, of whom three discontinued. The participants were randomly allocated to 9 weeks of continuous treatment with EV 2 mg + DNG 2–3 mg (n = 20), EE 0.03 mg + DNG 2 mg (n = 20), or DNG 2 mg (n = 19). Blood samples were collected at baseline and after 9 weeks. We assessed coagulation in vitro by thrombin generation using the Calibrated Automated Thrombogram. Thrombin generation was evaluated by lag time, time to thrombin peak, thrombin peak, and endogenous thrombin potential in response to tissue factor (1 pm). In vivo coagulation assessment was based on levels of prothrombin fragment 1 + 2 (F1 + 2) (thrombin generation) and D-dimer (fibrin turnover). Clinical trial registration: NCT02352090.

Results: Lag time and time to thrombin peak remained unaltered after exposure to EV + DNG, whereas EE + DNG shortened both lag time (mean percentage change −24%, 95% confidence interval [CI] −32% to −15%; p < 0.01) and time to thrombin peak (−26%, 95% CI −37% to −16%; p < 0.01). EV + DNG induced lower thrombin peak and endogenous thrombin potential than EE + DNG (peak; +45%, 95% CI 22%–67% vs +147%,95% CI 96%–198%; p < 0.01, and endogenous thrombin potential; +26%, 95% CI 15%–38% vs +64%, 95% CI 51%–76%; p < 0.01). Median F1 + 2 levels remained unchanged with EV + DNG (p = 0.22) but increased within normal ranges with EE + DNG (from 152 pmol/L, 95% CI 127–206] pmol/L to 194 pmol/L, 95% CI 149–250 pmol/L, p = 0.04). The within-group change in D-dimer levels was not significant in any of the groups. DNG alone did not affect these biomarkers.

Conclusions: Both in vitro and in vivo thrombin generation was lower after exposure to EV + DNG compared with EE + DNG. The lower thrombin generation measures after treatment with EV + DNG indicate less enhancement of coagulation potential and suggest that EV may be favorable to EE as a component of combined oral contraceptives.