Coumadin Clinic
Warfarin is an anticoagulant (anti = against and coagulant = clotting). It is a strong medicine that slows your body’s ability to form a blood clot. It is also known as a “blood thinner”. Warfarin is also knows as Coumadin (Coumadin is the brand name for Warfarin).
Click below on the following links to read about a particular section on warafin (coumadin).
All About Warfarin/Coumadin
Factors Affecting INR Results
FAQ
Summary
All About Warfarin (Coumadin)
How do I take warfarin?
Take your warfarin only as directed by your health care provider. Try to take it the same time each day.
Why do I need my blood tested?
Blood tests called INRs (International Normalized Ratio) indicate how well the medicine is working. This test will be needed as long as you are taking warfarin.
What is an INR?
INR stands for International Normalized Ratio; it shows how well the warfarin is working. The INR will be numbers such as 1.7, 2.0, 2.6, 3.8, 5.8.
The higher the number, the longer it will take your blood to clot. If your INR is too high, you have a higher chance of bleeding. An INR that is too low does not protect your from blood clots that could form.
Your healthcare provider will tell you what your target range INR is.
What do I do if I miss a dose?
Warfarin is a strong medicine that lasts for days. Check with your healthcare provider if you miss a dose. Don’t panic, missing a dose is not life-threatening, but get back on you schedule as soon as possible. Never take extra Warfarin tablet to catch up unless instructed by your healthcare provider.
What are signs of trouble?
- Bleeding gums, blood in urine, or black or tarry stools
- Unusual or excessive bruising
Factors Affecting INR Results
As with most medications, it is important to understand how warfarin might interact with anything else that you consume – whether you consume it daily or only once in a while. The three most important factors to consider are Vitamin K, alcohol, and any other medications or supplements that you take.
Vitamin K
The #1 dietary concern is Vitamin K. Produced by your body as part of the clotting process, vitamin K is also found in many foods. Does this mean you should reduce your dietary intake of vitamin K? No. Your healthcare provider will base your recommended warfarin dose on your regular diet, so the key to maintaining an effective dosage level is to consistently follow your normal eating habits.
Common foods that are high in Vitamin K include:
- Broccoli
- Brussels sprouts
- Cabbage
- Salad oils (canola, soybean, olive)
- Olestra (Olean)
- Mayonnaise
- Collard, mustard, and turnip greens
- Chick peas
- Parsley
- Scallions
- Lettuce, endive, kale, watercress
- Soy protein
- Spinach
Alcohol
The factors that help your blood to clot are made in the liver, which is also responsible for breaking down any alcohol you drink – whether it is beer, wine, or spirits.
Even if you drink in moderation and only occasionally, alcohol can increase your INR. One of the worst things you can do is “binge” on a large number of alcoholic drinks over a short period of time. This can cause gastrointestinal bleeding that can be hard to stop.
Because of these risks, your healthcare provider will likely recommend that you avoid drinking any alcohol while your are taking warfarin.
Drugs and Supplements
Because warfarin can interact with many drugs and supplements, tell your healthcare provider if you regularly consume any of these items:
- Acetaminophen (Tylenol)
- Acid receptor antagonists (Tagamet, Zantac, Prevacid)
- Antibiotics
- Antihistamines
- Aspirin (including aspirin containing creams)
- Diabetes drugs (oral)
- Diuretics (water pills)
- Herbal teas containing tonka beans, sweet clover or sweet woodruff)
- Herbal supplements
- Ibuprofen (Advil, Motrin, Nuprin)
- Naproxen (Aleve, Orudis KT)
- Non-steroidal anti-inflammatory drugs (NSAIDS)
- Oral contraceptives
- Estrogen
- Steroids
- Thyroid drugs
- Vitamin supplements with Vitamin K
Frequently Asked Questions
- What time of day should I take warfarin? We recommend you take it at night. Your blood will be drawn for testing during the day, allowing us to obtain your INR results and advise you if a does change is needed.
- Can stress affect my INR? Stressful events, physical or psychological can elevate the INR.
- May I eat green leafy vegetables while taking warfarin? Yes, the guiding principle is to refrain from making sudden changes in your in intake of these vitamin K-containing foods.
- What should I do if a healthcare practitioner other than the one who regulates my warfarin prescribes a new medication or discontinues a medication that I was previously taking? Inform whoever regulates your warfarin about any changes as soon as possible.
- What happens if I have to discontinue warfarin temporarily for an operation or diagnostic procedure? Inform the provider who regulates your warfarin (before the procedure, if possible). You may receive alternate instructions while warfarin is temporarily discontinued.
- How long will I have to take warfarin? Lifelong, if you have a mechanical heart valve. If you are taking it for atrial fibrillation, it’s managed on a case-to-case basis. For deep vein thrombosis (DVT/blood clots) and pulmonary emboli (PE), the optimal duration is controversial, but commonly a minimum of 6 months.
Summary
When warfarin is used there are multiple drugs and foods that can interact with and affect the INR. Regular monitoring of the INR is essential to provide optimal dosing (reach and maintain target range). The INR is usually obtained several times weekly at the initiation of warfarin treatment.
Once a stable INR and warfarin dose are achieved, the INR frequency is gradually reduced to once a month. More frequent monitoring is essential when other medications are started or discontinued. This includes over-the-counter medications, vitamins, natural herbs, and minerals. The commonly prescribed antiarrhythmic drug amiodarone and many antibiotics markedly increase the anticoagulant effect of warfarin and increase the INR.
Sudden binges or abstinence from foods containing vitamin K such as spinach, broccoli, and brussel sprouts will affect the INR. The combination of alcohol and warfarin will increase the likelihood of bleeding, even in the situations when the INR does not rise. Sometimes important INR fluctuations can occur without an identifiable reason.
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