Medication Nurse Assistant Talk: Monday March 3, 2008 Topic of discussion: Anticoagulant Coumadin (Warfarin).

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Stuart Hilary Welch
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1 Medication Nurse Assistant Talk: Monday March 3, 2008 Topic of discussion: Anticoagulant Coumadin (Warfarin). Learning Objectives: 1. History of Warfarin 2. Pharmacokinetics / Pharmicodynamics of warfarin 3. Lab monitoring 4. Dietary implications of Vitamin K 5. Common drug:drug interactions 6. Side effects I. History of Warfarin The history of warfarin began back in the 1920 s in the mid west when a group of cattle developed a hemorrhagic disease. The source of the bleeding was traced to the ingestion of improperly cured sweet clover. In 1939 the hemorrhagic agent was isolated and identified as bishydroxycoumarin (dicumarol), at the University of Wisconsin. While dicumarol was being studied as an anticoagulant for animals and humans, a similar compound was synthesized and initially marketed for a rodenticide (rat poison). Warfarin was given its name from an acronym derived from the first letter s of the Wisconsin Alumni Research Foundation. By 1955 it was available commercially as an anticoagulant for the treatment of thromboembolic disease (Ansell, Oertel & Wittkowsky, 2001). II. Pharmacokinetics / Pharmicodynamics of warfarin: A. Warfarin is a medication that is prescribed to people to reduce the risk of blood clot formation. Blood clots may lead to stroke, pulmonary embolism and possible death. Many people have come to think of warfarin as a blood thinner type of medication. This is truly a myth. warfarin does not make blood thin however it does interfere with the body s chemical process by which blood clots are formed, prolonging the time it takes to form a blood clot. B. Warfarin is metabolized in the liver, the same site as vitamin K synthesis. C. Mechanism of Action: Warfarin exerts their anticoagulation effect by interfering with the hepatic synthesis of vitamin K dependent clotting factors. Factors II, VII, IX and X as well as co-factors protein C and S. 1

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3 III. Lab Monitoring A. The International Normalized Ratio (INR) is the lab test that is done to measure the level of anticoagulation. B. INR Goal Ranges (CHEST, 2004). 1. A-fib = DVT / PE = Aortic Valve = Mitral Valve = IV. Dietary implications of Vitamin K A. Vitamin K is the antidote for warfarin and with significant po intake will affect the INR. B. Dark Green Leafy Vegetables are most common source of vitamin K however there are many other foods that contain vitamin K as well. 1. Mayonnaise 2. Pistachio nuts 3. Green Tea (very high). C. Nutritional Supplements: 1. Ensure 2. Promod 3. Slim-Fast 4. Boost V. Common drug : drug interactions (Dartmouth-Hitchcock Medical Center, 2006). A. Most Antibiotics will affect the INR leading to an increased level 1. Cipro 2. Bactrim 3. Azithromycin B. Steroids 1. prednisone, 2. medrol C. Antifungal 1. diflucan D. Cardiac drug: 1. Amiodarone E. Non-Steroidals (NSAIDs) 1. Aleve 2. Naprosyn 3. Advil / Mortrin (ibuprofen) F. Other OTC drugs: 1. Sudafed 2. Pepto Bismol 3. Alka Seltzer 4. NyQuil 3

4 5. Pepcid AC G. Herbal Products: 1. Ginseng 2. Kava kava 3. Garlic 4. Ginko 5. Danshen 6. Licorice VI. Side effects: Increased Bleeding / Bruising (Dartmouth-Hitchcock Medical Center, 2006). A. Common: Slight Bleeding: 1. Gums while brushing teeth 2. Occasional nosebleed 3. Minor cuts that stops within a few minutes 4. Menstrual bleeding a little heavier than normal Major Bleeding: Call MD or go to Emergency Department: 5. Change in color of urine (iced tea or cranberry). 6. Change in color of bowel movements (black tar). 7. Excessive bleeding from nose 8. Coughing up or throwing up of coffee colored or bright red substance 9. Severe abdominal pain 10. Unexplained bruises 11. Cut that will not stop bleeding within 10 minutes 12. Trauma to head B. Less Common: 1. GI upset / diarrhea 2. Loss of appetite 3. Unusual hair loss 4. Purple Toe Syndrome 5. Warfarin Necrosis Other Resources: Dartmouth-Hitchcock Medical Center Anticoagulation Program: _id=40755 PTINR.com DVT.net 4

5 Reference: Ansell, J., Oertel,L.,. Wittkowsky, A. (2001). Warfarin Pharmacology History Managing Oral Anticoagulation Therapy 2001;4B-1:1 CHEST. (2004). The Seventh ACCP Conference on Antithrombotic and Thrombotic Therapy 126(3). Dartmouth-Hitchcock Medical Center, (2006). My guide to Coumadin/warfarin therapy. Reprinted with permission from Cedar Rapids Community Anticoagulation Clinic. Scott, C., Trujillo,T. (2006). Hemorrhage and recombinant factor VIIa. Advanced Emergency Nursing, 28(4),

How to Take Coumadin /Warfarin. Blood Tests

How to Take Coumadin /Warfarin Please take your pills as directed. The amount of Coumadin /Warfarin each person needs is different. The dose is based on a blood test called the INR. The amount of medication