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To which class of drugs does heparin belong?
Anticoagulants.
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What are the indications associated with heparin?
Prophylaxis and treatment of thromboembolic disorders.
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What is unique about the chemical structure of heparin?
It is an extremely large (6,000 - 20,000 D), highly sulfated, negatively charged sugar.
Must be administered IV.
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What is heparin's target MOA?
Heparin potentiates the action of antithrombin by acting as a catalyst for antithrombin-dependent deactivation of thrombin and other clotting factors.
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As per heparin's MOA, what effects does it have on the body's tissues?
- Inactivation of thrombin (IIa), IXa, Xa, XIIa, and plasmin.
- Ultimately, the conversion of fibrinogen to fibrin is prevented.
- LPL is stimulated, resulting in increased FFA.
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Heparin increases the activity of antithrombin by _______ x.
Heparin increases the natural activity of antithrombin (a hepatic enzyme) by about 1,000 x.
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What are some adverse effects associated with heparin?
- HIT (1-2% incidence): heparin binds to platelet factor 4, and an immune response ensues against platelets. Antibody-platelet complexes aggregate and can cause, thrombosis and/or tissue death.
- Thrombosis (if body-stores of antithrombin run out).
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What drug may be used as an antidote to heparin overdose (which would actually cause thrombosis)?
Protamine sulfate.
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What lab parameter should be monitored to check for heparin efficacy/toxicity? What is its normal value? Is it desirable to be within this normal value?
- aPTT
- Normal value: 26-33 seconds
- Technically, you would want the aPTT to be above this value.
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What lab parameters would indicate that a patient is experiencing bleeding and should not receive heparin?
Hgb, Hct, fecal occult blood test.
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