Journal of Pharmacy Practice

Thrombophilia alters normal hemostasis, shifting the balance in favor of thrombus formation. Inherited conditions include factor V Leiden (FVL), prothrombin G20210A mutation, deficiencies in natural anticoagulants (antithrombin [AT], protein C, and protein S), hyperhomocysteinemia, and elevations in clotting factors (factors VIII and XI). Although FVL and prothrombin mutation are common disorders, deficiencies in the natural anticoagulants are rare. The risk of initial thrombosis conferred by inherited thrombophilia varies with the highest risk in those homozygous for either FVL or prothrombin mutation, or with AT deficiency. In the nonpregnant patient, the presence of a thrombophilia does not affect treatment of an acute event. Although vitamin B supplementation has been shown to decrease the levels of homocysteine, the treatment has failed to show a benefit in thrombus prevention and is therefore not recommended.

Acquired thrombophilia is associated with an increased risk of venous thromboembolism (VTE). Antiphospholipid syndrome (APS) is the most prevalent acquired thrombophilia and is associated with both venous and arterial thromboses. Human immunodeficiency virus (HIV) is another form of acquired thrombophilia. Risk factors associated with VTE in this population include those related to the disease itself, host factors, and the pharmacotherapy for HIV. A significant proportion of VTE events occur in patients with malignancies. There is an increase in mortality associated with patients having cancer who experience VTE when compared to patients having cancer without VTE. Combination oral contraceptive (COC) use infers risk of thromboembolic events. The risk is dependent upon the presence of an underlying inherited thrombophilia, the estrogen dose, and generation of progestin. Patients at highest risk of VTE include those receiving high-dose estrogen and fourth-generation, progesterone-containing contraceptives. With the exception of APS, thrombophilia status does not alter the acute treatment of an initial VTE in nonpregnant patients.

Pregnancy is associated with an increased risk of venous thromboembolism (VTE), with a reported incidence ranging from 0.49 to 2 events per 1000 deliveries. Risk factors include advanced maternal age, obesity, smoking, and cesarian section. Women with a history of previous VTE are at a 4-fold higher risk of recurrent thromboembolic events during subsequent pregnancies. Additionally, the presence of concomitant thrombophilia, particularly factor V Leiden (homozygosity), prothrombin gene mutation (homozygosity), or antiphospholipid syndrome (APS), increases the risk of pregnancy-related VTE. Low-molecular-weight heparin (LMWH) and unfractionated heparin (UFH) are the drugs of choice for anticoagulation during pregnancy. LMWH is preferred due to ease of use and lower rates of adverse events. Women with high thromboembolic risk particularly those with a family history of VTE should receive antepartum thromboprophylaxis. Women with low thromboembolic risk or previous VTE caused by a transient risk factor (ie, provoked), who have no family history of VTE, may undergo antepartum surveillance. Postpartum anticoagulation can be considered in women with both high and low thromboembolic risk.

Although controversial, screening for thrombophilia has become common. Testing for antiphospholipid antibodies is indicated in order to guide treatment decisions if there is clinical suspicion for antiphospholipid syndrome. The utility of identifying other thrombophilias in symptomatic venous thromboembolism (VTE) is questionable, as the risk of recurrence does not appear to be increased by an appreciable degree with the most common disorders (heterozygosity for factor V Leiden or prothrombin mutation). Although recurrence appears to be increased in those with homozygous or multiple abnormalities and potentially deficiencies in natural anticoagulants, screening to detect these conditions is difficult to justify based on their rarity. The American College of Chest Physicians’ current guidelines note the increased risk of recurrence with idiopathic, proximal events regardless of thrombophilia status. They suggest duration of anticoagulation therapy be based on location and provoking factors rather than whether or not the individual has a thrombophilia. Because routine prophylaxis in asymptomatic individuals with thrombophilia is not recommended, screening of asymptomatic family members is difficult to justify. Screening prior to prescribing combination oral contraceptives is not cost effective, may result in unwanted pregnancies, and may have little effect on the overall rate of VTE.