What drugs and supplements can interact with warfarin?

Warfarin, like any other medication, can interact with foods, other drugs, vitamins or herbal supplements. Be ready to provide your doctor with a complete list of everything you're taking.

Drugs that can interact with warfarin include:

  • Aspirin or aspirin-containing products
  • Ibuprofen (Advil, Motrin, others) or naproxen (Aleve, Anaprox)
  • Acetaminophen (Tylenol, others) or acetaminophen-containing products, especially when the dose of acetaminophen exceeds 1,500 milligrams a day
  • Many antibiotics
  • Heparin
  • Cold or allergy medicines
  • Birth control pills
  • Medications that treat abnormal heart rhythms, such as amiodarone

This isn't a complete list. Many other medications interact with warfarin. You should always consider that a new medication could interact with warfarin until your doctor, nurse or pharmacist tells you otherwise.

Supplements that can interact with warfarin include:

  • Fish oil and omega-3 supplements
  • Vitamin K
  • Alfalfa
  • Bromelains, a type of supplement that comes from pineapples (pineapple itself doesn't interact with warfarin)
  • Coenzyme Q10 (ubidecarenone)
  • Cranberry extracts
  • Danshen
  • Dong quai
  • Evening primrose oil
  • Garlic
  • Ginkgo biloba
  • Ginseng
  • Glucosamine
  • St. John's wort
  • Willow bark
  • Wintergreen

What foods and drinks might interact with warfarin?

If you sometimes eat foods that are high in vitamin K — such as soybean and canola oils, spinach or broccoli — tell your doctor. Vitamin K can affect how your blood clots and how warfarin protects you.

Garlic and black licorice also may interact with warfarin, so talk to your doctor if you eat a lot of these foods.

Eating cranberries or drinking cranberry juice can affect the way warfarin works and can increase your risk of bleeding. While an occasional glass of cranberry juice is unlikely to injure you, you should avoid drinking it regularly.

Drinking alcohol also can affect the way warfarin works. Talk to your doctor about drinking alcohol while taking warfarin. While having an occasional drink shouldn't create a problem, excessive drinking or binge drinking can greatly increase your bleeding risk.

What should you do if you forget a dose?

If you forget to take a dose of warfarin within 12 hours of when you were supposed to take it, take it as soon as you remember and get back on your daily dosing schedule. If you forget to take a dose and it has been more than 12 hours, wait until the next dose is due. Unlike some other medications, doubling your warfarin dose could greatly increase your risk of side effects.

Always talk to your doctor if you're unsure if you took your warfarin as directed. If you follow your doctor's dosing instructions and tell all your health care providers that you take warfarin, you'll be at a much lower risk of dangerous interactions and warfarin side effects. Talk to your doctor, nurse or pharmacist if you have any concerns about warfarin. They can be a valuable source of information.

Feb. 16, 2012 See more In-depth