Anticoagulants inhibit various components of the coagulation cascade to prevent thrombus formation, used in conditions at risk for thrombosis.
Heparin and Low Molecular Weight Heparins (LMWHs)
Examples: Enoxaparin
Mechanism: Heparin activates antithrombin III, which inactivates thrombin and factor Xa; LMWHs have more selective inhibition of factor Xa.
Use: Deep vein thrombosis (DVT), pulmonary embolism (PE), atrial fibrillation (AF), prophylaxis in surgery.
Side Effects: Heparin-induced thrombocytopenia (HIT), bleeding; LMWHs have a lower risk of HIT.
Warfarin
Mechanism: Vitamin K antagonist; inhibits synthesis of vitamin K-dependent clotting factors II, VII, IX, and X.
Use: AF, mechanical heart valves, DVT, PE.
Side Effects: Bleeding, skin necrosis, teratogenicity; requires monitoring of INR.
Direct Oral Anticoagulants (DOACs)
Examples: Dabigatran, Rivaroxaban, Apixaban, Edoxaban
Mechanism: Direct inhibition of thrombin (Dabigatran) or factor Xa (Rivaroxaban, Apixaban, Edoxaban).
Use: Similar indications to warfarin but with fixed dosing and no routine monitoring.
Side Effects: Bleeding, gastrointestinal disturbances; fewer dietary interactions.
Direct Thrombin Inhibitors
Examples: Argatroban, Bivalirudin
Mechanism: Directly inhibit thrombin, preventing fibrin formation.
Use: HIT, percutaneous coronary interventions.
Side Effects: Bleeding, potential for thrombocytopenia.
Clinical Considerations:
Balancing Act: Coagulants must be used cautiously to avoid thrombosis, while anticoagulants require careful monitoring to prevent bleeding.
Reversal Agents: Availability and knowledge of reversal agents (e.g., vitamin K for warfarin, protamine sulfate for heparin) are critical in managing adverse effects.