Q. I take Coumadin. Should I be concerned about possible interactions with foods or other drugs?
A. Yes. A recent report in the Archives of Internal Medicine indicates that there are more potential interactions between Coumadin and foods and Coumadin and other drugs than previously thought. However, you don’t necessarily need to eliminate suspect foods from your diet, just maintain a consistent intake and be sure your doctor knows about significant changes in your diet. Here’s why.
How Warfarin Works. Coumadin is the brand name for the drug warfarin, the most commonly prescribed oral anticoagulant (blood thinner) in the U.S. It’s used to prevent blood clots in people with heart disease, ischemic stroke, irregular heartbeats and artificial heart valves, for example. Clotting starts with vitamin K, which is required for the activation of several blood clotting factors. Doctors prescribe Coumadin because it reduces the amount of active vitamin K and interferes with the cascade of events that clots blood.
The effectiveness and safety of the drug are directly related to proper dosage, so your doctor will monitor your blood level of Coumadin and fine-tune the dose as needed, often because of changes in diet, other medications, alcohol and liver disease.
Foods to Monitor. Because green leafy vegetables are rich in vitamin K, people taking Coumadin are sometimes told to avoid these veggies. But that’s not nutritionally wise nor necessary. What you need to avoid is drastic changes in dietary sources of vitamin K. Suddenly eating a lot of spinach or kale, for example, might decrease Coumadin‘s effectiveness.
Experts suggest eating no more than 1/2 cup per day of cooked spinach, kale, turnip greens or collards, or no more than 1 1/2 cups of Brussels sprouts or 3 cups of raw spinach, broccoli or Romaine. Other foods that may decrease Coumadin‘s effectiveness include large amounts of avocado, soy milk, sushi made with seaweed, and green tea. Foods that increase Coumadin‘s blood-thinning action include mango, cranberry juice, grapefruit juice and alcohol (if you have liver disease). Keep your intake of all these foods moderate and as consistent in your diet as possible.
Supplements to Reveal. Any multivitamin that contains vitamin K will inhibit warfarin’s action to some degree. On the flip side, fish oil supplements and herbal preparations containing ginseng or dong quai may increase warfarin’s ability to prevent blood clotting, risking excessive bleeding.
Other Drugs of Which to Be Wary. The list of drugs?Rx and over-the-counter’that interact with warfarin is long. Included, ironically, are some common cardiovascular drugs, such as statins, fibrates and aspirin, as well as nonsteroidal anti-inflammatories, such as ibuprofen (Motrin), Celebrex and Vioxx, which exacerbate warfarin’s effect on bleeding.
EN‘s Bottom Line. Coumadin has been used safely for years. But because of the potential for interactions, be sure to tell your doctor what foods you eat regularly and all the medications you take, including supplements and over-the counter preparations like aspirin. Check with your doctor and pharmacist before drastically changing your diet, taking a new supplement or refilling an old prescription.