Heparin (5000IU) is a parenteral anticoagulant, a highly sulfated glycosaminoglycan derived from porcine intestinal mucosa or bovine lung. It acts as an immediate-acting anticoagulant by potentiating the activity of antithrombin III (AT III), leading to rapid inactivation of coagulation factors IIa (thrombin), IXa, Xa, XIa, and XIIa. In the Indian context, it is a critical, low-cost drug for prophylaxis and treatment of thromboembolic disorders, widely available in hospital and clinical settings. It is not absorbed orally and must be administered via injection.
Adult: **Prophylaxis (SC):** 5000 IU every 8-12 hours. **Treatment (IV):** Initial bolus of 5000 IU (or 80 IU/kg), followed by continuous IV infusion of 18 IU/kg/hr (approx. 1300 IU/hr for 70kg adult), adjusted to target aPTT (typically 1.5-2.5 times control). **ACS (IV):** 60-70 IU/kg bolus (max 5000 IU) followed by 12-15 IU/kg/hr infusion.
Note: **SC:** Deep subcutaneous injection into abdominal wall fat layer, alternating sites. Do not aspirate or massage. Use fine needle (26-30G). **IV:** For bolus, administer slowly over at least 1 minute. For infusion, use an infusion pump. NEVER give IM (risk of hematoma). Solutions are clear; inspect for particulate matter. Use preservative-free formulations for neonates.
Heparin binds to Antithrombin III (AT III), a natural plasma protease inhibitor, via a specific pentasaccharide sequence. This binding induces a conformational change in AT III, dramatically accelerating (by ~1000-fold) its ability to inactivate serine protease coagulation factors, primarily Thrombin (Factor IIa) and Factor Xa. For thrombin inhibition, heparin must bind simultaneously to both AT III and thrombin (requiring a chain length of at least 18 saccharide units). Inhibition of Factor Xa requires only the pentasaccharide-AT III binding.
Pregnancy: **US FDA Category C.** Does not cross placenta. Drug of choice for anticoagulation in pregnancy (especially 2nd & 3rd trimester) for treatment/prevention of VTE and mechanical heart valves. Long-term use (>1 month) associated with maternal osteoporosis. Protamine can be used if needed for reversal.
Driving: No direct effect. However, if dizziness or weakness occurs due to bleeding, patient should avoid driving or operating machinery.
| Oral Anticoagulants (Warfarin, Acenocoumarol) | Increased risk of bleeding; monitor INR closely during overlap. | Major |
| Antiplatelets (Aspirin, Clopidogrel, NSAIDs like Diclofenac) | Additive antiplatelet effect increases bleeding risk. | Major |
| Thrombolytics (Streptokinase, Alteplase) | Profound increase in bleeding risk. | Major |
| Other Heparins/LMWH (Enoxaparin) | Additive anticoagulant effect. | Major |
| Digoxin, Tetracyclines, Nicotine | May partially counteract heparin's anticoagulant effect. | Moderate |
| Nitroglycerin (IV) | May reduce heparin's anticoagulant effect; monitor aPTT closely. | Moderate |
| Antihistamines, Digitalis, Tetracycline | May interfere with heparin's action. | Moderate |
| ACE Inhibitors (Ramipril, Enalapril) | Increased risk of hyperkalemia. | Moderate |
Same composition (Heparin (5000IU)), different brands: