Will warfarin interact with other medicines I take?
Yes. Warfarin interacts with many other medicines, including:
Prescription medicines
Over-the-counter medicines
Herbal products
Supplements
Vitamins
When medicines interact with warfarin, it can cause harmful bleeding or clots. The warfarin dose you are given will be adjusted for the other medicines you are taking. Any change to your medicines could cause an interaction. Ask your pharmacist if you have any questions about warfarin and your other medicines. Tell your health care provider within three days if you start taking a new medicine, stop a medicine, or change the dose of any of your medicines. You may need more frequent INR tests because of the change in your medicines.
You can take some over-the-counter medicines while you are taking warfarin. Please check with your pharmacist about medicines that are safe. Medicines that are safe may include:
Acetaminophen (Tylenol®) for fever, headaches, or pain
Antihistamines for allergies: Examples of antihistimines include diphenhydramine (Benadryl®) and loratidine (Claritin® and Alavert®). Products that contain only antihistamines will not interact with your warfarin. Be careful of combination products since other medicines in the product may cause problems.
The following are examples of common medicines to stay away from when you are on warfarin. These can all be purchased without a prescription and can be harmful for you. Be sure to read labels carefully.
Aspirin (except as prescribed by your doctor)
Products containing aspirin such as Pepto- Bismol®, Alka-Seltzer®, Kaopectate®, Bayer cold and flu, Excedrin®
Non-steroidal anti-inflammatory drugs such as ibuprofen (Advil®) or naproxen (Aleve®)
Cimetidine (Tagamet®) used for heartburn
Vitamin E supplements
Herbal products especially garlic, gingko, ginseng, and ginger: Garlic and ginger used in food will not cause problems. However, supplements do interact because they have a much larger amount of garlic and ginger.
Vitamin products containing more than 25 mcg of vitamin K per tablet (be sure to check label)
Some examples of common prescription medicines that can interact with your warfarin include:
Antibiotics (medicines used to treat infections)
Seizure medicines
Amiodarone (a medicine used for heart problems)
Medicines used to lower your cholesterol
Can changes in my health affect my warfarin therapy?
Any changes in your overall health can cause changes in your INR. Let your health care provider know within three days of any changes in your health. If you have sudden sickness, let your health care provider know as soon as possible. Some examples include diarrhea, vomiting, fever, change in appetite, worsening heart failure, or infection.
Can changes in my diet affect my warfarin therapy?
Yes. Your dose of warfarin is affected by how much vitamin K you eat. The amount of vitamin K you eat should be the same from week to week. Do not make sudden changes in your diet.
We have provided you with a vitamin K chart that shows how much vitamin K chart is in a serving of common foods. It also groups foods as low, medium, and high based on how much vitamin K they contain. For example, the list includes many vegetables and tells you which vegetables contain a low, medium or high amount of vitamin K. High amounts of vitamin K are found in green vegetables such as spinach, broccoli, and cabbage.
If you like foods high in vitamin K, then you will want to plan to have the same number of servings of those foods each week. If you don’t usually eat the foods high in vitamin K, then you may want to avoid these foods while you are on warfarin. The important thing is to be consistent. Eat the same number of high and medium vitamin K containing foods each week.
Beware—some types of food may have vitamin K added—read labels carefully. This is common with foods used by people who want to lose weight or who need nutritional supplements. Examples of these kinds of products include SlimFast, Ensure, Boost, and Instant Breakfast.
Other things in your life such as travel, or changes in your health, can also lead to changes in what you eat and in your INR. Tell your health care provider about any major changes in your diet within three days.
Does drinking alcohol affect my warfarin therapy?
Yes. Limit your alcohol to no more than two drinks per 24-hour period. Drinking more than this amount can increase your INR and lead to bleeding problems. Tell your health care provider if you drink more than two drinks a day so your INR can be checked more often.
