ASK THE DOCTOR: Medication, food interacts with warfarin
By DR. JIM MITTERANDO
The Patriot LedgerQ I take Coumadin for atrial fibrillation. My blood tests are never consistent and my dosage is always changing. My wife worries about all the things that can interact with this medicine especially my nightly scotch and soda. Can I drink with this medicine? What food should I avoid? How often should I have my blood tested? Is the generic drug as good?
A Coumadin (generic name warfarin) is a commonly used medication to prevent blood clots. In small, controlled doses this medication is safe and prevents strokes and deadly blood clots to the lungs. Too much warfarin can be deadly by causing bleeding.
People taking warfarin require a regular blood test called an INR, which measures the level of anticoagulation (clot prevention). The goal INR, generally, is 2 to 3. People with heart valves require an INR of 2.5 to 3.5 to prevent problems. Often, your doctor may need to adjust your warfarin dose as a result of a fluctuating INR.
When first starting warfarin, people require frequent blood testing to determine the right dose. When the INR is stable, it can be tested every month or two.
Many medications and foods interact with warfarin, possibly causing problems. Some interactions raise the INR too high, which may cause bleeding. Often, interactions decrease the INR too low, rendering the medication ineffective.
In the past, people were advised to avoid foods with vitamin K because vitamin K reduces warfarin’s efficacy and lowers the INR. These days, I recommend regular, moderate consumption of these healthy vegetables, but keep it fairly consistent so that your doctor can adjust your warfarin dosage to match your diet. If your diet varies quite a bit, your INR levels can swing very high or low.
Foods rich in vitamin K include: asparagus, broccoli, cauliflower, cabbage, kale, spinach, brussel sprouts, chick peas/garbanzo beans (hummus), soybeans (tofu, soymilk), lentils (dried peas and beans), dark green, leafy vegetables, green lettuce (romaine, bib and red leaf), collard, mustard, turnip and beets, green tea (tea in Chinese restaurants), parsley (tabbouleh).
Foods with excessive vitamin K to avoid include: large amounts of onions (greater than ¼ cup), avocado (guacamole), egg yolks (not more than four per week), liver, seaweed (sushi or algae).
Alcohol consumption does affect how the liver metabolizes warfarin. Therefore, alcohol intake should be consistent with no more than one or two drinks per day. Excessive alcohol can dangerously raise the INR.
Many medications (including over-the-counter, prescriptions and herbal supplements) affect how the liver metabolizes warfarin. Prescription medicine tends to be taken consistently so that over time, its effect on your INR can be factored into your warfarin dose. Sporadic usage of medicines is more troublesome because this leads to greater fluctuations of the INR. For example, antibiotics and antifungal pills can raise the INR and increase the risk of bleeding. As a result, sometimes your doctor may ask that your INR be checked three days after starting a medicine to make sure it has not severely affected the warfarin.
Aspirin, ibuprofen (Advil, Motrin) and naproxen (Alleve) can delay blood clotting and in general should be avoided when taking warfarin. Tylenol (acetaminophen) is generally considered safe but can rarely raise the INR.
Many herbal products can interact with warfarin. You should check with your physician before starting any herbal medicine when taking warfarin and possibly have more frequent blood tests initially. Ginger, garlic and gingko should not be taken with warfarin since they may delay blood clotting and increase the risk of bleeding.
Vitamin K should be avoided since this inhibits warfarin. If possible, choose a multivitamin that does not have vitamin K. Avoid large amounts of vitamins A, C or E.
Generic warfarin is identical to the name brand Coumadin. The FDA mandates very strict guidelines so that generic drugs have the same efficacy as name brand drugs.
Warfarin is a medicine with both benefits and risks. The benefits outweigh the risks when:
- You take it daily
- Your INR is monitored regularly
- You eat and drink sensibly.
If you have problems with frequent falls, then the risks of bleeding may outweigh its benefits. If you notice your INR fluctuates, discuss with your physician any recent changes in diet or medications.Dr. Jim Mitterando is a family doctor at Cohasset Family Practice and a staff member at South Shore Hospital in Weymouth.
Readers should send questions to: Ask the Doctor, The Patriot Ledger, P.O. Box 699159, Quincy, MA 02269-9159, or by E-mail to his attention at features@ledger.com.
Questions of general interest will be answered in this column. The information in this column is not intended to diagnose individual conditions, and individual replies are not possible. Readers should see their own doctors about specific problems.
Copyright 2003 The Patriot Ledger
Transmitted Tuesday, January 14, 2003