Anticoagulant

An anticoagulant is a class of medication that inhibits the coagulation (clotting) of blood. These drugs prevent or reduce coagulation, preventing thrombosis, and extending clotting times.

Mechanism of Action

Anticoagulants work at various points of the normal coagulation process. Some, like heparin, inhibit specific clotting factors, while others, like warfarin, inhibit the formation of clotting factors in the liver by blocking the action of vitamin K. Direct oral anticoagulants (DOACs) like dabigatran, rivaroxaban, apixaban, and edoxaban, act on specific single steps in the coagulation pathway.

Indications

Anticoagulants are indicated for the prevention and treatment of a variety of conditions involving thrombotic complications, including atrial fibrillation, venous thromboembolism (VTE), pulmonary embolism, and in patients undergoing certain types of surgery, particularly orthopedic procedures like hip and knee replacements which have a high risk of post-operative blood clots.

Adverse Effects

The primary adverse effect of anticoagulants is bleeding. Risk factors for bleeding include high doses of anticoagulants, elderly age, female sex, renal and liver diseases, and concurrent use of other medications that increase bleeding risk. Antidotes are available for some anticoagulants, like vitamin K for warfarin and idarucizumab for dabigatran.

Monitoring

The effects of anticoagulants are monitored using a variety of laboratory tests. Warfarin therapy is typically monitored with the International Normalized Ratio (INR), whereas heparin is monitored with the activated partial thromboplastin time (aPTT).

References

• Garcia DA, Baglin TP, Weitz JI, Samama MM (2012). "Parenteral anticoagulants: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines". Chest. 141 (2 Suppl): e24S–e43S. doi:10.1378/chest.11-2291.
• Holbrook A, Schulman S, Witt DM, Vandvik PO, Fish J, Kovacs MJ, Svensson PJ, Veenstra DL, Crowther M, Guyatt GH (2012). "Evidence-based management of anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines". Chest. 141 (2 Suppl): e152S–e184S. doi:10.1378/chest.11-2295.

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