Indian Express
22 May 2010

People using oral anti–coagulants often have to undergo an unnecessary change in lifestyle. Dr Upendra Kaul clears up the misconceptions
Patients on long–term Warfarin treatment need not avoid Vitamin K rich foods altogether, since these are heart healthy foods. Follow normal diet. The important thing is to avoid a drastic change of diet ORAL anti–coagulants are very frequently prescribed drugs are required by a significant number of patients –often for life.

There are several issues linked with the intake of these drugs, like avoiding several types of foods and beverages and medicines.

But sometimes, due to lack of awareness both among patients and doctors, such patients are condemned to a complete change in their lifestyle. But this is altogether wrong and unnecessary.And it is important for patients to know about blood thinners and what they do.

What are Blood Thinners
Blood thinners –also called anticoagulants –include drugs like Warfarin, Warf, Acitrom, Dindaven etc. This group, however, should not be confused with Aspirin and Clopidogrel, which are anti–platelet agents. Anti–platelet agents reduce the stickiness of platelets and are not anti–coagulants.

The common reasons why these drugs are needed on a long term are:

Clot formation in leg veins or deep vein thrombosis

Clot formation in lung arteries

Atrial fibrillation –irregular and chaotic beating of upper chambers of the heart

After mechanical replacement of heart valves

After a heart attack complicated by clot in the ventricle or atrium

After a brain stroke

After certain surgical procedures

Background ofWarfarin
The drug was discovered in 1939, when a large number of cattle in some parts of the US and Canada died of bleeding because of eating improperly cured feeds made from common varieties of sweet clover.

The causative compound was identified as dicoumarol, which was used as a rat poison in the 1940s. Human use of Warfarin started in 1950s but it gained popularity after being used to treat US president Eisenhower after a heart attack in the mid–1950s. These days it is the fourteenth largest selling prescription drug in the US and Europe.

How it Works
Warfarin blocks the effect of Vitamin K in liver. Vitamin K is required to create blood clots and prevent bleeding –a necessary procedure for healing of injuries.

Warfarin hampers the body’s ability to make clots and is used to prevent formation of harmful clots.

It does not dissolve the existing clots, but prevents them from becoming larger. The action starts within 24 hours of taking the drug.

But full effect takes around four days and lasts for three to five days.

Dosage and INR
The dosage of the drug varies and is decided by the doctor on basis of a blood test called pro–thrombin time. It is also called an INR (International Normalised Ratio) test and basically measures the time taken for blood to clot. In most cases, the INR range is kept between 2 and 3. For people with metallic heart valves and few other conditions, the range is kept between 2.5 and 3.5.

If the INR is within the prescribed range, it means things are normal. Levels below 2 mean that the blood is thicker and the patient is at risk of clot formation and the medicine dose needs to be increased. If the INR crosses 3.5, it means blood has become very thin and places the patient at a high risk of bleeding. In this case the dosage needs to be lowered.

Warfarin and Food

Patients on Long Term Warfarin treatment need not avoid vitamin K rich foods altogether, since these are heart healthy foods.Foolow normal diet.The important things is to avoid a drastic change of diet.

Food sources rich in Vitamin K can interfere with the action of Warfarin. These include green leafy vegetables like cabbage, broccoli, spinach, lettuce, cauliflower, mustard greens, organ meats like liver and kidney. Patients on long–term Warfarin treatment need not avoid Vitamin K rich foods altogether, since these are also heart healthy foods.

The best thing is to follow your normal diet. If such foods are part of your regular diet, then you may continue with them. The important thing is to avoid a drastic change of diet.

Many dietary supplements also contain Vitamin K. Herbal medicines and supplements can also lead to disturbances in Warfarin action and just because the product has been advertised as “a natural product” it does not mean it is safe. Some of these supplements include multi vitamins, cranberry herbal products, ginseng, garlic, fenugreek, ginger, clove, primrose oil. It is better to avoid these.

Some Tips

While taking Warfarin, do not make sudden changes in diet with out discussing it with your doctor.Do not go on a weight loss diet.

Do not take new dietary supplements, vitamins, minerals or herbs without discussing it with your doctor. It may lead to serious complications.

Call the doctor if you are unable to eat for several days or if you have a stomach upset, diarrhoea, or fever. If you cannot eat, it will decrease the amount of Vitamin K in your body and can affect Warfarin action.

Warfarin and Other Drugs
Warfarin interacts with several drugs and can lead to several complications. So it is very important to inform your doctor regarding any additional medication and herbal productsandsupplementsyoutake.

This do esnotme an you cannot take other medicines. But a close monitoring is required.

Commonly Asked Questions
What is the best time to take Warfarin?
It should be preferably taken in the evening. But the most important thing is to take it at the same time every day. The advantage of evening dose is in case a test has been done to check INR in the morning, the dose can be changed the same day if need be. The blood test should not be done soon after taking the medicine.

Should it be taken after meals?
Warfarin should not be taken immediately after a meal. It should be taken one–and–a–half–hour before or after the meal. Food impairs its absorption from the stomach.

For how long should the drug be taken?
This varies from patient to patient. For some it is lifelong and for others it is temporary. Your doctor can advise you on this.

?Should special precautions be taken during travel?
Remember to take the medicine regularly. Stick to normal diet and avoid excessive alcohol. In case you are away for a long period, your doctor can advise you on blood tests. If INR is grossly beyond the target levels, inform your physician or a local doctor before taking the next dose.

Currently, a new group of drugs is being developed which will probably replace Warfarin. These agents –Rivaroxaban and Dabigatran –when available, will not need any blood monitoring. Their interactions with food and other medicines will also be negligible.