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Therapeutic anticoagulation 

Therapeutic anticoagulation

Chapter:
Therapeutic anticoagulation
Author(s):

David Keeling

DOI:
10.1093/med/9780199204854.003.161602_update_002

Update:

Enhanced discussion of indications for and use of oral direct inhibitors of thrombin and factor Xa.

Updated on 29 Oct 2015. The previous version of this content can be found here.
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date: 24 March 2017

Low molecular weight heparins (LMWH) have largely replaced unfractionated heparin. Their much more predictable anticoagulant response combined with high bioavailability after subcutaneous injection means that the dose can be calculated by body weight and given subcutaneously without any monitoring or dose adjustment. Their widespread use resulted in most patients with deep vein thrombosis being managed as outpatients, and this is also increasingly the case for uncomplicated pulmonary embolism.

New oral direct inhibitors of anticoagulation that specifically target thrombin or factor Xa have been developed and are now an option for treating acute venous thromboembolism (VTE) and for stroke prevention in atrial fibrillation.

Particular issues—(1) in patients with cancer and VTE giving LMWH for the first 6 months of long-term anticoagulant therapy has been shown to be superior to vitamin K antagonist; (2) high-dose loading regimens of warfarin are unnecessary and may increase the risk of overanticoagulation and bleeding; (3) warfarin for venous thromboembolism and atrial fibrillation should be given with a target INR of 2.5 (range 2.0–3.0); for patients with prosthetic heart valves the target INR is usually greater; (4) indefinite anticoagulation is required for patients with atrial fibrillation or a mechanical heart valve; for venous thromboembolism a careful clinical decision is required regarding duration of treatment; (5) for patients with atrial fibrillation choiceanticoagulation is much more effective than aspirin in preventing stroke; (6) if warfarin needs to be stopped for surgery, full-dose heparin does not have to be given perioperatively unless the risk of thromboembolism is high, and warfarin can be continued in patients having dental extractions.

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