What medications can affect Activated Partial Thromboplastin Time (APTT)?

From the Guidelines

Medications that can affect Activated Partial Thromboplastin Time (APTT) include anticoagulants such as heparin, dabigatran, and other direct oral anticoagulants (DOACs).

Medications Affecting APTT

• Heparin: a glycosaminoglycan that binds to and enhances the activity of antithrombin III, reducing thrombin generation via inhibiting coagulation factors (XIIa, IXa, XIa, and Xa) 1
• Dabigatran: a direct thrombin inhibitor that competitively inhibits thrombin and thus prevents the conversion of fibrinogen to fibrin, which can prolong APTT in a non-linear manner at higher concentrations (≥ 200 ng/mL) 1
• Rivaroxaban: a direct, reversible inhibitor of activated factor X (FXa), which can also prolong APTT, although this assay is less sensitive than the PT 1
• Apixaban and Edoxaban: direct, reversible inhibitors of FXa, which may have a mild or modest effect on APTT, depending on the reagent used 1

Important Considerations

• The sensitivity of APTT to these medications can vary depending on the reagent used and the patient's individual characteristics, such as renal function and bioavailability 1
• A normal APTT does not necessarily rule out the presence of these medications, and other coagulation assays, such as PT or viscoelastic tests, may be necessary to fully assess the patient's coagulation status 1
• The use of these medications can increase the risk of bleeding, and careful consideration should be given to their use in patients with a high risk of bleeding or those who require urgent surgery or invasive procedures 1

From the Research

Medications Affecting Activated Partial Thromboplastin Time (APTT)

The following medications can affect APTT:

• Direct oral anticoagulants (DOACs) such as dabigatran, rivaroxaban, and apixaban 2
• Warfarin, which can increase APTT in a dose-dependent manner 3
• Heparin, which is often used in conjunction with warfarin and can affect APTT 3
• Dabigatran, which can increase APTT in a linear pattern with marginal slopes 4, 5

Mechanism of APTT Prolongation

The mechanism of APTT prolongation by these medications is as follows:

• DOACs inhibit specific coagulation factors, leading to an increase in APTT 2
• Warfarin inhibits the production of vitamin K-dependent coagulation factors, leading to an increase in APTT 3
• Heparin enhances the activity of antithrombin, leading to an increase in APTT 3
• Dabigatran directly inhibits thrombin, leading to an increase in APTT 4, 5

Clinical Implications

The clinical implications of APTT prolongation by these medications are:

• APTT may not be a reliable measure of anticoagulant activity in patients taking DOACs 2
• Warfarin can affect APTT, leading to potential misinterpretation of heparin therapy 3
• Dabigatran can increase APTT, but the relationship between APTT and dabigatran level is not always reliable 4, 5
• APTT may be used to monitor anticoagulant therapy in certain clinical circumstances, such as in patients taking heparin or warfarin 6