Heparin is an anticoagulant indicated for thromboprophylaxis and to treat thrombosis associated with a variety of conditions such as pulmonary embolism and atrial fibrillation. Unfractionated heparin (UH) is a heterogenous preparation of anionic, sulfated glycosaminoglycan polymers with weights ranging from 3000 to 30,000 Da.
- Mechanism
- Curator reviewed
Under normal circumstances, antithrombin III (ATIII) inactivates thrombin (factor IIa) and factor Xa. This process occurs at a slow rate. Administered heparin binds reversibly to ATIII and leads to almost instantaneous inactivation of factors IIa and Xa The heparin-ATIII complex can also inactivate factors IX, XI, XII and plasmin. The mechanism of action of heparin is ATIII-dependent. It acts mainly by accelerating the rate of the neutralization of certain activated coagulation factors by antithrombin, but other mechanisms may also be involved. The antithrombotic effect of heparin is well correlated to the inhibition of factor Xa. Heparin is not a thrombolytic or fibrinolytic. It prevents progression of existing clots by inhibiting further clotting. The lysis of existing clots relies on endogenous thrombolytics.
- Primary indication
- Unfractionated heparin is indicated for prophylaxis and treatment of venous thrombosis and its extension, prevention of post-operative deep venous thrombosis and pulmonary embolism and prevention of clotting in arterial and cardiac surgery.Curator reviewed · 31 structured indications
- First approval
- Canada, 1998 · United States, 1943
- Also known as
- Heparinic acid · Unfractionated heparin
- Code names
- CY 216 · CY 222 · KB 101 · OP 386 · OP 622
- Brand names
Resolves to
What you can answer from here — as of July 17, 2026
Which drugs share a target with Heparin, and which of those have an active Phase 3 trial?
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