Pharmacogenetics Newsletter

Volume 1, Issue 5, 05/06/2009

Question

How do oral contraceptives (birth control pills) increase the risk of clots or venous thromboembolisms (DVTs and pulmonary embolisms) in patients with the genetic polymorphism, Factor V Leiden?

Answer

The first case report of clot formation or venous thromboembolism (VTE) attributed to the use of oral contraceptives (birth control pills) occurred in 1961.(1)  This female suffered a pulmonary embolism shortly after starting the oral contraceptives.  Since this inciting event, considerable debate has continued regarding the absolute risk of developing a symptomatic deep vein thrombosis (DVT) and/or pulmonary embolism (PE) as a result of taking various formulations of oral contraceptives.(2-9)  Consequently, there has been significant research done to determine which factors contribute to the development of VTE in patients taking oral contraceptives. 

With research and additional clinical experience, a number of risk factors for the development of VTE have emerged.  These include the type of estrogen containing oral contraceptive being used, the dose of estrogen, smoking, age of the patient, past history of VTE, surgery, major trauma, pregnancy, malignancy and prolonged immobilization.(5,6,8)  In addition, a number of genetic risk factors have been identified.  The most common genetic risk factors for developing VTE include antithrombin, protein C and S deficiency, factor V Leiden, and prothrombin 20210A mutation.(7,10-17)  The focus of this newsletter will be how does having factor V Leiden significantly increase the risk for VTE......To read the full answer please LOGIN or SUBSCRIBE NOW.