Risk of Venous Thrombosis with Subdermal Hormone-Releasing Implants

Introduction to Subdermal Implants

• The American Heart Association recommends that subdermal implants releasing etonogestrel do not induce a prothrombotic state during the first 6 months of use, according to recent evaluations 1

Comparison with Other Hormonal Contraceptives

• The American College of Cardiology and other guideline societies suggest that combined oral contraceptives increase the risk 2-4 times (RR 2.14, IC 95%: 1.64-2.81) compared to non-users 2, 3

Mechanism of Safety

• The presence of only progestin (without estrogen) in subdermal implants is fundamental to their safety profile, as estrogen is the main component responsible for increasing the thrombotic risk in combined contraceptives, by decreasing antithrombin III and protein S, creating a procoagulant environment 1

Clinical Considerations

• The increased risk in the first year of use (characteristic of combined oral contraceptives with RR 3.49) is not observed with subdermal implants 3
• The dose-response relationship between estrogen/progestin and venous thrombosis is not relevant for progestin-only implants 1