Ans. A: Powerful anticoagulant only in vivo Heparin is a powerful and instantaneously acting anticoagulant, effective both in vivo and in vitro. At low concentrations of heparin, factor Xa mediated conversion of prothrombin to thrombin is selectively affected. The anticoagulant action is exeed mainly by inhibition of the factor Xa as well as thrombin (Ha) mediated conversion of fibrinogen to fibrin. Routes of Administration are l/ V infusion and S/C injection. Heparin should not be given by IM injection. Contraindications Thrombocytopenia When lab facilities for monitoring of TT/ APTT (Thrombin time/ activated paial thromboplastin time) are not available. Bleeding condition like active peptic ulcer, esophageal varices, piles etc, and blood dyscrasias. Uncontrolled hypeension, bacterial endocarditis. Recent surgery or trauma. Menstruation. Hypersensitivity to heparin. Intracranial haemorrhage. Proliferative retinopathy. Severe liver disease and renal failure. Aminoglycosides are incompatible with heparin and should not be given in the same cannula. Drug Interactions Potentially fatal: - Use with care in conjunction with oral anticoagulants and avoid concomitant use of drugs affecting platelet functions like aspirin, dipyridamole, phenylbutazone, indomethacin and other NSAIDs. Non-fatal: - Glycerl trinitrate reduces the activity of heparin by increasing its excretion. - Digitalis, tetracyclines, nicotine may decrease the effects of heparin. Adverse Effects Common effects: - Haemorrhage - can be minor (bleeding from venepuncture sites) or major (internal bleeds). - Thrombocytopenia - due to platelet aggregation induced by heparin. Local irritation - pain, erythema, ulceration. Rare effects: - Hypersensitivity - chills, fever, uicaria, anaphylactoid reactions may occur. Following Long-term use - osteoporosis, SCOT and SGPT elevation can occur. Drug Toxicity Continuous infusion has led to serious complications (hemorrhage) and acute thromobocytopenia, leading to shock and death. Treatment of Toxicity Slow intravenous infusion of protamine sulfate (calculate the dose of protamine sulphate to be given by the principle: 1 mg of protamine sulphate neutralizes 100 units of heparin). Not more than 50 mg of protamine sulphate to be injected per dose. Alternatively, give fresh blood or plasma or clotting factors.