Name: Heparin
Class: Antithrombotic Agent (Anticoagulant)
Mechanism: Catalyzes complex formation btwn. plasma antithrombin III and various serine proteases of the coagulation pathway, including thrombin and activated factors IX, X, XI, & XII. Effect primarily due to thrombin inhib. Prevents further clot formation and thrombus propagation. Does not alter organized clots.
Absorp.: IV, continuous IV®immed. onset. SC®1-2 hr onset w/variable bioavail.
Dist.: Metabolism.: Hepatic.
Excretion, t½: Rel. short t½. ¯ t½ w/pulm. embolism. t½ w/hepatic cirrhosis or end-stage renal disease.
Toxicity/S.E.s: 1° = bleeding. Thrombocytopenia (bovine > porcine)—mild, severe (delayed onset; can occur w/heparin resistance ® thromboembolism & DIC). Long-term use ® osteoporosis. Non-teratogenic, but discontinue prior to delivery.
Utility: Symptomatic calf vein thrombi or thrombi extending above the popliteal vein, pulm. embolus, atrial fibrillation, valvular heart disease, CAD, adjunct to post-MI thrombolytic therapy. Use in general surgery for E on oral contraceptives.
Special Features: Primarily used for venous thromboses. Most widely used antithromb. agent. Monitor PTT to achieve desired dose—1.5-2.5x normal PTT is therapeutic. recurrence rate if PTT < style=""> Few drug interactions.