From the Guidelines
Medications that can prolong the Activated Partial Thromboplastin Time (APTT) include heparin, low molecular weight heparins like enoxaparin, direct thrombin inhibitors, and certain other anticoagulants as outlined in recent clinical guidelines 1.
Medications Affecting APTT
The most common medications that prolong APTT are:
- Heparin (both unfractionated heparin and low molecular weight heparins like enoxaparin)
- Direct thrombin inhibitors (such as bivalirudin, argatroban, and dabigatran)
- Lupus anticoagulant antibodies Other medications that can affect APTT include:
- Warfarin (especially when the INR is significantly elevated)
- High-dose aspirin
- Certain antibiotics like penicillins at high doses Some herbal supplements like ginkgo biloba, garlic, and ginseng may also contribute to APTT prolongation.
Mechanism of APTT Prolongation
The mechanism behind APTT prolongation varies by medication:
- Heparin works by enhancing antithrombin III activity
- Direct thrombin inhibitors directly block thrombin function
- Warfarin reduces vitamin K-dependent clotting factors
Clinical Considerations
When interpreting prolonged APTT results, it's essential to consider the patient's medication history, as these drugs can affect test results without necessarily indicating a pathological bleeding disorder. Monitoring APTT is particularly important when using unfractionated heparin therapy, where the therapeutic range is typically 1.5-2.5 times the control value, as indicated in studies such as 1. Given the most recent evidence, the use of heparin and low molecular weight heparins like enoxaparin is supported by guidelines for the management of venous thromboembolism in patients with cancer 1. It is crucial to consult the latest clinical guidelines and patient-specific factors when managing anticoagulation therapy to minimize the risk of morbidity, mortality, and to improve the quality of life.
From the FDA Drug Label
Warfarin sodium tablets may increase the activated partial thromboplastin time (aPTT) test, even in the absence of heparin Argatroban is a direct thrombin inhibitor indicated: (1) For prophylaxis or treatment of thrombosis in adult patients with heparin-induced thrombocytopenia (HIT) The dose for heparin-induced thrombocytopenia without hepatic impairment is 2 mcg/kg/min administered as a continuous infusion Heparin: Allow sufficient time for heparin’s effect on aPTT to decrease before initiating Argatroban Injection therapy
The medications that can prolong the Activated Partial Thromboplastin Time (APTT) are:
From the Research
Medications that Prolong APTT
The following medications can prolong the Activated Partial Thromboplastin Time (APTT):
- Warfarin: Warfarin can markedly affect APTT, with an increase of 1.0 in the international normalized ratio resulting in a 16-second increase in APTT 4
- Unfractionated heparin (UFH): UFH can prolong APTT, and its effects on APTT are additive to those of warfarin 4
- Low-molecular-weight heparins (LMWHs): LMWHs, such as ardeparin, tinzaparin, dalteparin, and enoxaparin, can also prolong APTT, although to a lesser extent than UFH 5
- Direct thrombin inhibitors (DTIs): DTIs, such as argatroban, bivalirudin, and lepirudin, can prolong APTT and affect international normalized ratio (INR) values 6, 7
Mechanism of APTT Prolongation
The mechanism of APTT prolongation by these medications involves:
- Inhibition of thrombin generation: Warfarin, UFH, and LMWHs inhibit thrombin generation, leading to an increase in APTT 4, 5, 8
- Inhibition of factor Xa: LMWHs and DTIs inhibit factor Xa, which can also contribute to APTT prolongation 5, 8
- Interference with coagulation factor assays: DTIs can interfere with coagulation factor assays, leading to inaccurate results 6
Clinical Implications
The prolongation of APTT by these medications has important clinical implications, including:
- Monitoring of anticoagulation therapy: APTT is commonly used to monitor anticoagulation therapy with UFH and LMWHs 4, 5
- Risk of bleeding: Prolongation of APTT can increase the risk of bleeding, particularly when multiple anticoagulant medications are used concurrently 4, 7
- Need for alternative monitoring methods: In some cases, alternative monitoring methods, such as plasma diluted thrombin time, may be necessary to accurately assess anticoagulation therapy 6