Heparin inhibits reactions that lead to the clotting of blood and the formation of fibrin clots both in vitro and in vivo. Heparin acts at multiple sites in the normal coagulation system. Small amounts of heparin in combination with antithrombin III (heparin cofactor) can inhibit thrombosis by inactivating activated Factor X and inhibiting the conversion of prothrombin to thrombin. Once active thrombosis has developed, larger amounts of heparin can inhibit further coagulation by inactivating thrombin and preventing the conversion of fibrinogen to fibrin. Heparin also prevents the formation of a stable fibrin clot in inhibiting the activation of the fibrin stabilizing factor.

Bleeding time is usually unaffected by heparin. Clotting time is prolonged by full therapeutic doses of heparin; in most cases, it is not measurably affected by low doses of heparin.

Heparin sodium is indicated for:

Atrial fibrillation with embolization:

• Treatment of acute and chronic consumption coagulopathies (disseminated intravascular coagulation);
• Prevention of clotting in arterial and heart surgery;
• Anticoagulant therapy in prophylaxis and treatment of venous thrombosis and its extension;
• (In a low-dose regimen) for prevention of postoperative deep venous thrombosis and pulmonary embolism in patients undergoing major abdomino-thoracic surgery or who for other reasons are at risk of developing thromboembolic disease
• Prophylaxis and treatment of pulmonary embolism; 

Intravenous-

Prophylaxis of re-occlusion of the coronary arteries following thrombolytic therapy in myocardial infarction

• Adult: 60 U/kg (max: 4,000 U) or a bolus of 5,000 U if streptokinase was used, followed by 12 U/kg/hr (max: 1,000 U/hr) w/ a treatment duration of 48 hr.

Intravenous-

Peripheral arterial embolism, Unstable angina, Venous thromboembolism

• Adult: 75-80 U/kg or 5,000 U (10,000 U in severe pulmonary embolism) IV loading dose followed by 18 U/kg or 1,000-2,000 U/hr continuous infusion. Alternatively, intermittent inj of 5,000-10,000 U 4-6 hrly.
• Child: 50 U/kg loading dose, followed by an infusion of 15-25 U/kg/hr.
• Elderly: Lower dosages may be required.

Subcutaneous-

Prophylaxis of postoperative venous thromboembolism

• Adult: 5,000 U given 2 hr before surgery then 8-12 hrly for 7 days or until the patient is ambulant.

Subcutaneous-

Venous thromboembolism

• Adult: 15,000-20,000 U 12 hrly or 8,000-10,000 U 8 hrly.
• Child: 250 U/kg bid.
• Elderly: Lower dosages may be required.

Current or history of heparin-induced thrombocytopenia; generalised or local haemorrhagic tendency, including uncontrolled severe HTN, severe liver insufficiency, active peptic ulcer, acute or subacute septic endocarditis, intracranial haemorrhage or injuries and operations on the CNS, eyes and ears, and in women with abortus imminens; epidural anaesth during birth; locoregional anaesth in elective surgical procedures (in patients receiving heparin for treatment rather than prophylaxis).

Hypersensitivity reactions (e.g. chills, fever, urticaria, asthma, rhinitis); painful, ischaemic and cyanosed limbs; osteoporosis (in long-term admin), suppression of aldosterone synthesis leading to hyperkalaemia, cutaneous necrosis, delayed transient alopecia, priapism, rebound hyperlipaemia; increased serum concentrations of AST and ALT, prolonged prothrombin time; local irritation, erythema, mild pain, haematoma or ulceration on inj site.

Overdose Effects

Symptoms: Bleeding (nose bleeds, blood in urine or tarry stools may be noted as the 1st sign of bleeding).

Management: May give protamine sulfate by slow IV infusion over 10 min to treat severe bleeding (1 mg of protamine sulfate neutralises approx 100 U of heparin). Max: 50 mg as a single dose.

Patient with increased risk of bleeding complications, HTN, DM, pre-existing metabolic acidosis. Do not use in catheter lock flushing. Hepatic and renal impairment. Elderly. Pregnancy and lactation.

Use in Special Populations

Pediatric Use: There are no adequate and well controlled studies on heparin use in pediatric patients. Pediatric dosing recommendations are based on clinical experience. Carefully examine all Heparin Sodium Injection vials to confirm choice of the correct strength prior to administration of the drug. Pediatric patients, including neonates, have died as a result of medication errors in which vials have been confused with “catheter lock flush” vials

Pregnancy & Lactation

Pregnancy Category C. Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus.

Nursing Mothers: Due to its large molecular weight, heparin is not likely to be excreted in human milk, and any heparin in milk would not be orally absorbed by a nursing infant. Benzyl alcohol present in maternal serum is likely to cross into human milk and may be orally absorbed by a nursing infant. Exercise caution when administering Heparin Sodium Injection to a nursing mother.