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Anticoagulants are "agents that prevent blood clotting".[1] They interfere with coagulation and may be used to prevent embolism and thrombosis.

Anticoagulation is dangerous due to drug toxicity and should be managed in a systematic manner.[2]

Vitamin K antagonists


For more information, see: warfarin.

Warfarin is a commonly used oral anticoagulant that interferes with the Vitamin K dependent coagulation co-factors.

Indirect thrombin inhibitors


Heparins bind to and activate the enzyme inhibitor antithrombin III. The activated antithrombin III then inactivates thrombin, factor Xa, and components of coagulation.

Unfractionated heparin

Details of the usage of heparin are available in clinical practice guidelines by the American College of Chest Physicians[3]:

Heparin dose may also be adjusted by using an anti-Xa assay to measure heparin function, which is related to heparin levels. The goal heparin level is 0.3 to 0.7 U/mL for unfractionated heparin but a higher level for low molecular weight heparin.[4][5][6]

Low molecular weight heparin

For more information, see: Low molecular weight heparin.

Selected low molecular weight heparins
  Prophylaxis dose Full dose Comments
30 mg twice daily
40 mg once daily
1 mg/kg/dose every 12 hours
1.5 mg/kg once daily
more information is at Enoxaparin
After loading, 2500 to 5000 int. units daily 150 int. units/kg up to 18,000 int. units) once daily
dosing is complicated and more information is at DailyMed
If creatinine clearance is less then 30 mL/minute, monitor anti-Xa levels

The last dose of low molecular weight heparin prior to coronary artery bypass surgery should occur 24 hours before the procedure in order to prevent high residual anti-Xa levels.[7]

Direct thrombin inhibitors (antithrombins)

Direct thrombin inhibitors (antithrombins) bind directly to thrombin[8] and are used for heparin-induced thrombocytopenia and during percutaneous coronary interventions.[9]

Low molecular weight heparins may provide better anticoagulation for prophylaxis of deep venous thrombosis among orthopedic patients than direct thrombin inhibitors because the latter may increase bleeding complications.[12] However, if anticoagulation is started before surgery, direct thrombin inhibitors may be more effective.

Factor Xa inhibitors

Warfarin combined with heparin

Warfarin combined with heparin did not benefit survivors of acute myocardial infarction in a randomized controlled trial.[21]

Warfarin combined with heparin reduced events, but increased bleeding, among survivors of acute myocardial infarction in a randomized controlled trial.[22]

Adverse effects

Risk factors

Various risk factors, such as history of chronic obstructive pulmonary disease, prior gastrointestinal hemorrhage and anemia, have been identified.[23]

Bleeding is more likely when more than one antithrombotic is used.[24][25]

Accidental falls may not increase rate of major bleeding.[26]


In atrial fibrillation, the risk of bleeding can be estimated with the HAS-BLED clinical prediction rule.[27]

In acute acute coronary syndrome, the risk of bleeding with heparin can be estimated with a clinical prediction rule ( Additional clinical prediction rules are available.[28]


Proton pump inhibitors may reduce the risk of gastrointestinal hemorrhage among patients undergoing anticoagulation.[29]


"Prothrombin complex concentrate immediately and completely reverses the anticoagulant effect of rivaroxaban in healthy subjects but has no influence on the anticoagulant action of dabigatran at the PCC dose used in this study" according to a randomized controlled trial. [30]


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See also

External links