Venous Thromboembolism Risk with Transdermal Estrogen

Risk Comparison Between Routes of Administration

Transdermal estrogen has an odds ratio (OR) of approximately 0.9 (95% CI: 0.4-2.1) for VTE risk, which represents no significant increase compared to non-users 1, 2
In contrast, oral estrogen significantly increases VTE risk with an OR of 4.2 (95% CI: 1.5-11.6) 1, 2

Transdermal estrogen administration has a neutral effect on Sex Hormone Binding Protein (SHBP) levels, a marker of VTE risk 1

The American College of Rheumatology recommends that transdermal estrogen should be used with caution in women with antiphospholipid antibodies, as any estrogen therapy is contraindicated due to thrombosis risk 3, 4
The American College of Rheumatology also recommends that transdermal estrogen should be used with caution in patients with systemic lupus erythematosus (SLE), particularly those with moderate to severe disease activity 3
The American College of Rheumatology recommends that transdermal estrogen should be used with caution in women with multiple prothrombotic risk factors 3, 4

For women requiring hormone therapy who have a history of VTE or high VTE risk, the American College of Cardiology recommends that transdermal estrogen is the preferred route if estrogen therapy is necessary 1
When initiating transdermal estrogen therapy, the American College of Cardiology recommends using the lowest effective dose to further minimize any potential risk 1

Transdermal administration delivers lower systemic doses directly into the bloodstream, avoiding hepatic metabolism, which contributes to its safety profile 5

The contraceptive patch data showing increased VTE risk involves different estrogen doses and formulations than menopausal transdermal therapy, and should not be extrapolated to transdermal formulations 6

The American College of Cardiology recommends that topical estrogen can be safely used after a provoked DVT with negative thrombophilia workup, provided at least 3 months of anticoagulation have been completed and the provoking factor has resolved 7
The annual recurrence risk of provoked DVT is less than 1% after completing 3 months of anticoagulation, and anticoagulation beyond 3 months is not required for provoked VTE once the provoking factor is removed 7
A negative thrombophilia workup confirms the lack of inherited clotting disorders that would increase baseline risk, placing the patient in a low-risk category 7
If a patient develops VTE while on hormone therapy, they would need to discontinue hormonal therapy before stopping anticoagulation, according to the American Heart Association guidelines 8, 7
Hormonal therapy could be continued if there's a strong clinical indication, but anticoagulation must continue for the duration of hormone use, as recommended by the American College of Chest Physicians 8, 7
Women with hormone-associated VTE have approximately 50% lower recurrence risk compared to unprovoked VTE, based on data from the Journal of Thrombosis and Haemostasis 8, 7