Overview
This lecture covers key concepts of anticoagulant medications, specifically comparing heparin and warfarin, their uses, how they work, lab monitoring, and important antidotes.
Anticoagulant Purpose and Uses
- Anticoagulants prevent new blood clots and stop growth of existing clots.
- Commonly prescribed after heart attack (MI), or surgery (e.g., hip/knee) to reduce risk of DVT.
- Anticoagulants do not dissolve clots—only thrombolytics like TPA/alteplase do.
How They Work
- Anticoagulants block clotting factors in the coagulation cascade to prevent fibrin formation.
- Heparin acts quickly (within 20 minutes) and is given via injection (IV or subcutaneous).
- Warfarin starts working slowly (about 5 days to full effect) but lasts longer; it is taken orally.
Heparin vs. Warfarin Comparison
- Heparin is fast-acting and short-lasting; warfarin is slow-acting and long-lasting.
- Patients may receive both medications together for several days to allow warfarin to become effective.
Lab Monitoring and Antidotes
- Heparin is monitored with PTT (partial thromboplastin time); therapeutic range is 46–70 seconds.
- The antidote for heparin overdose is protamine sulfate.
- Labs must be carefully monitored: high values risk bleeding, low values risk clotting.
- Warfarin monitoring (not detailed here) typically uses INR, but this lecture focuses on heparin.
Key Terms & Definitions
- Anticoagulant — Drug that prevents clot formation or growth but does not dissolve existing clots.
- Thrombolytic — Drug that dissolves blood clots (e.g., TPA, alteplase).
- Heparin — Fast-acting injectable anticoagulant, monitored by PTT.
- Warfarin — Slow-acting oral anticoagulant, monitored by INR (not detailed here).
- PTT — Partial thromboplastin time, lab test for heparin efficacy.
- Protamine sulfate — Antidote for heparin overdose.
Action Items / Next Steps
- Review normal and therapeutic PTT values for heparin.
- Memorize the role and antidote of heparin.
- Know when to use anticoagulants versus thrombolytics.
- Prepare for quiz questions comparing heparin and warfarin.