Practical Guide for use of the blood thinner warfarin   Frank Barnhill M.D.
 

Blood thinners have been used for many years to prevent and treat blood clots in damaged arteries and veins throughout the human body. In the past 45 years, warfarin, an oral anticoagulant that interferes with Vitamin K based clotting factors, has become the drug most commonly used to treat and prevent unwanted blood clotting.

Currently, greater than thirty million warfarin prescriptions are filled in America every year and as our population continues to age, we anticipate that number to double in less than ten years. What follows includes practical information based on the assumption you are probably using warfarin or Coumadin therapy for one or more of these reasons:

Prevention of blood clots in the arms or legs following surgery 

Because of a blood clot in the veins of your legs or arms (called deep venous thrombophebitis)

After suffering a blood clot that traveled to the lungs (a pulmonary embolism)

After suffering a blockage in an artery or the blood vessels that carry oxygenated blood away from the heart

For treatment of chronic phlebitis or inflammation of blood vessels (usually in the legs)

Following heart surgery for valve replacement or repair of a defect that could cause a blood clot in the heart

For prevention of stroke and/or heart attack

As treatment for inheritable conditions (hypercoagulable states) that may cause sudden, unpredictable blood clotting, such as Leiden Factor V deficiency.

The single biggest problem patients have with warfarin therapy is keeping their clotting times in the range that both prevents clots and at the same time doesn’t expose them to greater risk of bleeding or hemorrhage.  Obviously, if you’re taking warfarin and your blood isn’t “thin enough,” you might suffer another blood clot in your legs, damage a heart valve, or have another heart attack or stroke.

In contrast, if your blood is “too thin,” you might bleed excessively from a simple cut or brushing your teeth, bruise easily, lose blood through your kidneys, bleed heavily during menstrual periods, or hemorrhage from a stomach ulcer or an irritated colon (diverticulitis). In addition, excessive anticoagulation or thinning of the blood can predispose you to sudden bleeding from small arteries found deep in the brain (called an intracerebral vascular accident or CVA). Some patients might develop a blood clot between the bones of the skull and the top of the brain called a subdural hematoma, following what one would normally consider a minor blow to the head.

With these thoughts firmly in mind, let’s discuss things that may interfere with warfarin therapy.

These may cause difficulty properly thinning your blood:

St. John’s wort   Green tea   Ginseng   Coenzyme Q10   Antacids   Laxatives   Stool softeners   Bismuth Subsalicylate

Foods that contain Vitamin K include:

Blueberries   Kiwi   Broccoli   Cabbage   Asparagus   Cauliflower   Green peas   Lettuce   Spinach   Brussels sprouts   Parsley   Endive   Kale   beef and pork liver   Mayonnaise   canola oil   Soybean oil   Soybeans   cashews   Margarine

These may cause excessive thinning of your blood:

Any vitamin supplement or foods containing Vitamin E, Vitamin A, or fish oil

Aspirin   Cimetidine   Anti-inflammatory drugs such as ibuprofen or naproxen    acetaminophen

Herbal and nutritional supplements containing:

Angelica root   Anise   Arnica flower   Asafoetida   Bogbean   Boldo-fenureek   Borage oil   Bromelain   Capsicum   Celery   Chamomile   Clove   Dashen   Devil’s claw   Dong quai   Feverfew   Garlic   Ginger    Ginkgo   Goldenseal   Horse chestnut   Licorice   Lovage root   Lycium barbarum (wolfberry)   Meadowsweet   Onion   Papain   Parsley   Passionflower   Poplar   Quassia   Quilinggao   Red clover   Rue   Sweet clover   Tumeric   Willow bark  

It should be obvious from these lists that what you eat and any other medicines you currently take can interfere with warfarin therapy, and you should avoid these altogether or at least discuss their use with your doctor.

Here are a few other things can you do to help “keep your blood thinned in the correct range.”

·        Take your warfarin at the same time very day. I usually ask my patients to do so just before bedtime.

·        Always take the pills with food or a snack and try to be consistent in what foods you use at that time.

·        Avoid drinking alcohol or taking other medications at the same time, unless cleared by your doctor.

·        Do not make major changes in your diet without discussing them with your doctor. Fad diets can cause serious problems in persons taking warfarin.

·        If you are unable to eat or take your medication for more than 24 hours due to an illness, you should phone your doctor.

·        Argue with the pharmacy if they try to change or substitute different brands of warfarin. The amount of the chemical in a single pill is so small that even a 5 percent content difference may cause your INR to fluctuate.

·        Follow your doctor’s schedule for testing to check your protime (INR) until it is in the therapeutic range. The protime or INR test measures how fast or how slow your blood will clot. Most experts agree an INR of 2.0 to 3.0 is an acceptable goal during warfarin therapy. However, if you have certain diseases of the kidneys or liver, your acceptable anticoagulation range will probably be much lower and will be determined on an individual basis. (The INR or international normalized ratio is a measure of the clotting tendency of your blood as compared to a standardized normal sample.)

·        Be sure to tell all doctors, dentists, chiropractors, physical therapists and massage therapists you are taking warfarin. They may need to alter their treatment plan based on your anticoagulant therapy.

I’m sure you’ll discover many other things that might interfere with warfarin therapy and place you at risk of additional blood clots or bleeding as you further your education. After all is said and done of course, you are your body’s keeper and should learn as much as you can about its care as you work in partnership with your doctor.

Dr. Frank

References:

The Journal of Family Practice, Vol. 58, No. 7, July 2009.

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