Anticoaculants - heparins Flashcards
Heparins - 2 drugs + 1 group
Unfractionated hepatin
Low-molecular-weight heparins (LMWHs)
Fondaparinux
LMWHs (3 drugs)
Enoxaparin
Dalteparin
Tinzaparin
Heparins - MOA
Inactivates clotting factors by potentiating antithrombin III
AT-III - functions
Most potent endogenous inhibitor of active factor X (Stuart factor) and II (thrombin).
LMWHs - MOA
Primarily inactivation of factor X (LMWH-AT-III complex has less affinity for thrombin than heparin-AT-III complex)
Heparin - adm
Parenterally, usually continuous IV infusion
How is the effect of heparin determined?
aPPT (activated partial thromboplastin time) - 1.5-2 times normal is adequate dosing. Not needed for LMWHs
LMWHs - adm
Subcutaneously
Heparins - adverse effects
Bleeding.
Heparin-induced thrombocytopenia (HIT) type I & type 2
Hyperkalemia (because of suppression of aldosterone secretion)
Type 1 HIT - mechanism and what should be done
Direct interaction between heparin and platelets that lead to a usually mild platelet aggregation. Reversible within 4 days despite continued heparin treatment.
25 % of pts.
Type 2 HIT - mechanism and what should be done
Immunoglobulin-mediated platelet inactivation with high risk of thrombotic complications. The drug must be discontinued.
Heparin - indications
Acute thromboembolic disorders: peripheral and pulmonary embolisms, venous thrombosis, coagulopathies (e.g. DIC)
Prophylaxis: Arterial and heart surgeries, blood transfusions, renal dialysis, blood sample collection, acute atrial fibrillation.
Low doses for prevention of DVT/pulmonary embolism in high-risk pts.
LMWHs - indications
Prevent venous thromboembolism after abdominal surgery and hip/knee replacements.
Unstable angina & non-ST-segment elevation MI, acute coronary syndrome, angioplasty
Enoxaparin - indications
Prevent DVT in severely immobilized pts.
Fondaparinux - adm and indications
Subcutaneous adm for DVT prophylaxis after hip fracture or hip/knee-replacements
