Other Names/Brands

Clotastop, Heparinol, Heparin Sodium, Hepagusan, Hico, Inviclot, Oparin, Thrombogel, Thromboflash, Thromecon, Thrombophob

Mechanism of Action

Heparin is an anticoagulant drug that works by inhibiting blood clotting by increasing the activity of antithrombin III, a naturally occurring protein in the body. When activated by heparin, antithrombin III inhibits enzymes important in the coagulation process, particularly thrombin (factor IIa) and factor Xa. This prevents the formation of fibrin, the main component of blood clots.

Heparin does not dissolve existing blood clots but prevents the formation of new ones and the expansion of clots. This drug is particularly useful for conditions such as deep vein thrombosis (DVT), pulmonary embolism (PE), and heart attacks.

Indications

Heparin is used to prevent and treat thromboembolic disorders such as deep vein thrombosis (DVT), pulmonary embolism, myocardial infarction, and unstable angina. It is also given during certain medical procedures, such as heart surgery, hemodialysis, or catheter placement, to prevent blood clots in medical devices or tubes.

Contraindications

Heparin should be avoided in patients with active bleeding (such as brain or gastrointestinal hemorrhage), severe blood clotting disorders, or a history of heparin-induced thrombocytopenia (HIT). Heparin is not recommended in patients with hypersensitivity or allergy to heparin or any of its components, as well as in patients with major trauma, brain or eye surgery, or other bleeding risks.

Side Effects

The most common side effect is bleeding, ranging from mild (bruising and bleeding gums) to severe (internal bleeding). Heparin can also cause thrombocytopenia, including the dangerous HIT. Other side effects include allergic reactions, irritation at the injection site, and osteoporosis with long-term use.

Preparations

Heparin is available as intravenous (IV) and subcutaneous (SC) injection solutions, in varying concentrations (1,000–10,000 IU/mL). It is also available as a low-dose flush (10–100 IU/mL) to maintain catheter patency and as a topical solution for local applications such as bruising or mild varicose veins.

Dosage

The heparin dosage depends on the indication and the patient's condition. For thrombosis prevention, 5,000 units are administered SC every 8–12 hours. For therapy, an IV bolus of 5,000–10,000 units is given, followed by a continuous infusion of 1,000 units/hour, adjusted according to the aPTT results. The dosage should also be adjusted in patients with renal impairment or a high risk of bleeding.

Safety of Drugs

Heparin is safe when used with close monitoring, particularly with aPTT monitoring for unfractionated heparin. The main risks are bleeding and HIT. Caution is needed in patients with kidney or liver disease, severe hypertension, or post-major surgery. Heparin is considered safe during pregnancy because it does not cross the placenta. The antidote for heparin is protamine sulfate.

Drug Interactions

Heparin can interact with other anticoagulants and antiplatelets (warfarin, aspirin, NSAIDs, and clopidogrel), increasing the risk of bleeding. Interactions can also occur with antibiotics, antihistamines, and drugs that affect the kidneys or liver, which can interfere with heparin's metabolism or effectiveness.

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