This article describes possible interactions with warfarin oral tablet. Interactions can cause a drug to have a different effect on the body than expected. Interactions can occur due to medications, alcohol, food, or certain health conditions.
Boxed warning: Risk of bleeding
Warfarin has a boxed warning for the risk of bleeding. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
See the end of this article for more information about this warning.
Other drugs and warfarin
The following warfarin drug interactions list for the oral tablet doesn’t include all drugs that may interact with warfarin.
Drug classes or drugs that may interact with warfarin oral tablet include:
- nonsteroidal anti-inflammatory drugs (NSAIDs), which include some over-the-counter drugs:
- drug examples: ibuprofen (Advil, Motrin), naproxen (Aleve, Naprosyn)
- what might happen: can increase the risk of bleeding
- corticosteroids:
- antiplatelets (prevent or hinder blood platelets from sticking together):
- drug examples: aspirin, clopidogrel (Plavix)
- what might happen: can increase the risk of bleeding
- other anticoagulants (blood thinners):
- drug examples: dabigatran (Pradaxa), apixaban (Eliquis)
- what might happen: can increase the risk of bleeding
- selective serotonin reuptake inhibitor (SSRI) and serotonin-norepinephrine reuptake inhibitor (SNRI) antidepressants:
- drug examples: fluoxetine (Prozac), venlafaxine (Effexor XR)
- what might happen: can increase the risk of bleeding
- certain antibiotics:
- drug examples: ciprofloxacin (Cipro), clarithromycin
- what might happen: can increase the risk of warfarin side effects, including bleeding
- certain blood pressure medications:
- drug examples: amlodipine (Norvasc), verapamil (Calan)
- what might happen: can increase the risk of warfarin side effects, including bleeding
- certain antiarrhythmics (prevent changes in heart rhythm):
- drug examples: amiodarone (Pacerone), propafenone (Rythmol SR)
- what might happen: can increase the risk of warfarin side effects, including bleeding
- certain medications that lower cholesterol:
- drug examples: cholestyramine (Locholest), atorvastatin (Lipitor)
- what might happen: can increase the risk of warfarin side effects, including bleeding, or make warfarin less effective
- certain HIV medications:
- drug examples: etravirine (Intelence), atazanavir (Reyataz)
- what might happen: can increase the risk of warfarin side effects, including bleeding
Talk with your doctor or pharmacist about drugs to avoid with warfarin.
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Other interactions and warfarin
Interactions can occur with supplements, foods, vaccines, and some lab tests. Below you can learn whether warfarin oral tablet has these interactions.
The information below doesn’t include all other possible interactions with warfarin.
Warfarin and supplements
Before taking warfarin oral tablet, tell your doctor and pharmacist about any herbs you take, as well as vitamins and supplements. Doing so may help you avoid interactions.
Warfarin can interact with certain supplements, including garlic, cranberry, and coenzyme Q10 supplements. Taking warfarin with garlic or cranberry supplements could increase the risk of bleeding. Taking warfarin with coenzyme Q10 supplements could make warfarin less effective.
If you have questions about other interactions that may affect you, talk with your doctor or pharmacist.
Warfarin interactions with herbs
Warfarin oral tablet can interact with several herbs.
Taking warfarin with certain herbs can increase your risk of bleeding. Examples of these herbs include:
Taking warfarin with certain other herbs can make warfarin less effective. Examples of these herbs include:
Because of this, ask your doctor or pharmacist before taking any of these products while taking warfarin oral tablet.
Warfarin interactions with vitamins
Warfarin oral tablet can interact with vitamin K. This vitamin may be taken for bone health and is often found in multivitamin supplements.
Taking warfarin along with vitamin K can make warfarin less effective.
Because of this, ask your doctor or pharmacist before taking any of these products while taking warfarin oral tablet.
Warfarin and food
Warfarin has interactions with several foods and drinks.
Consuming certain foods and drinks with warfarin may increase your risk of bleeding. Examples of these include:
Ask your doctor whether you should avoid or limit consumption of these foods and drinks while taking warfarin.
Consuming large amounts of foods that are high in vitamin K while taking warfarin can make warfarin less effective. It’s okay to eat these foods while taking warfarin. But it’s important to consume about the same amount of these foods each day. Examples of foods that are high in vitamin K include:
- leafy green vegetables, such as spinach and kale
- broccoli, cabbage, and cauliflower
- brussels sprouts
- peas
- lentils
- liver
- avocados
- soy products
- green tea
While taking warfarin, you generally should avoid making large changes to your diet. If you have questions about consuming certain foods or drinks with warfarin, talk with your doctor.
Warfarin and vaccines
Warfarin oral tablet isn’t known to interact with any vaccines. But this doesn’t mean interactions with vaccines can’t happen or won’t be identified later.
Because of this, talk with your doctor or pharmacist before receiving any vaccines while taking warfarin oral tablet.
Warfarin and lab tests
Warfarin oral tablet isn’t known to interact with lab tests. But this doesn’t mean interactions with lab tests can’t happen or won’t be identified later.
Because of this, talk with your doctor or pharmacist before having any tests while taking warfarin oral tablet.
Warfarin and cannabis or CBD
Reports have shown cannabis (commonly called marijuana) and cannabis products may interact with warfarin. Cannabidiol (CBD) is an example of a cannabis product.
Taking warfarin and cannabis or cannabis products may have varying effects. It may lead to an increased risk of bleeding. Or it could make warfarin less effective.
Before you take warfarin, tell your doctor and pharmacist if you use cannabis. Doing so may help prevent possible interactions.
Note: Cannabis is illegal at a federal level but is legal in many states to varying degrees.
Preventing warfarin interactions
You may be able to help avoid certain interactions with warfarin oral tablet. Before taking this drug, you may want to discuss possible interactions with your doctor and pharmacist.
Things to consider include:
- Whether you drink alcohol, smoke, or use cannabis.
- Other medications and herbs you take, as well as vitamins and supplements. Your doctor or pharmacist can help you fill out a medication list. And they can advise on any drugs to avoid with warfarin. Be sure to have them check for interactions with over-the-counter drugs you take and warfarin.
- Your diet and any warfarin interactions with foods you usually consume.
- What to do if you’re prescribed a new drug while taking warfarin oral tablet.
Taking warfarin exactly as prescribed can also help prevent interactions.
When to avoid warfarin
Certain health conditions or other factors could increase some risks with warfarin oral tablet. Because of this, doctors may not prescribe warfarin in these cases. These health conditions or other factors are called contraindications.
Here’s a list of contraindications for warfarin oral tablet:
- Pregnancy (unless you have a mechanical heart valve). If you’re pregnant, taking warfarin oral tablet may harm the developing fetus.
- Conditions that increase your tendency to bleed. If you have a condition that increases your tendency to bleed, taking warfarin can raise your risk of serious bleeding. Conditions that can increase the tendency to bleed include stomach ulcers and low platelet count.
- Upcoming or recent major surgery. Taking warfarin oral tablet before or after certain surgeries can increase your risk of serious bleeding. Examples include brain or spinal cord, eye, and abdominal surgeries.
- Upcoming or recent medical or dental procedures that have a high bleeding risk. Taking warfarin oral tablet before or after certain medical or dental procedures can increase your risk of serious bleeding. These procedures can include spinal injections.
- Very high blood pressure. If you have blood pressure that’s very high, taking warfarin oral tablet may increase your risk of serious bleeding.
- Past allergic reaction to warfarin. If you’ve ever had an allergic reaction to warfarin oral tablet, taking it again may cause another allergic reaction.
Before you start taking warfarin, tell your doctor if anything listed above relates to you. They can recommend whether you should take warfarin. If you have an upcoming surgery, dental procedure, or medical procedure, they can also discuss whether to stop taking warfarin beforehand.
Alcohol and warfarin
Warfarin oral tablet is known to interact with alcohol. Taking warfarin oral tablet and drinking alcohol can increase your risk of bleeding.
If you drink alcohol, talk with your doctor about whether it’s safe to consume it while taking warfarin oral tablet.
Health factors and warfarin
Certain medical conditions or other health factors may increase the risk of interactions with warfarin oral tablet. Keep in mind that interactions could lead to side effects or affect how well the drug works. Before taking warfarin, tell your doctor about your health history. They’ll determine whether warfarin is right for you.
These health conditions or other factors might interact with warfarin oral tablet:
* See the “When to avoid warfarin” section above for more information about this health factor.
What to ask your doctor
If you have questions about warfarin and possible interactions, talk with your doctor.
Questions you may want to ask your doctor include:
- Does my risk of interactions depend on my dosage of warfarin oral tablet?
- If I take a drug or have a condition that interacts with warfarin oral tablet, will I need additional monitoring?
- Do I need to tell you before making any changes to my diet or lifestyle while taking warfarin oral tablet?
Boxed warning for warfarin
Warfarin has a boxed warning for the risk of bleeding. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).
Warfarin helps prevent blood clots by making it harder for your blood to form them. If you already have blood clots in your body, warfarin can prevent the clots from becoming larger. Because warfarin thins your blood, it can increase your risk of serious or life threatening bleeding.
While you’re taking warfarin, your doctor will order a blood test to regularly check how quickly your blood clots. This is called a prothrombin time test, and it measures the time using an international normalized ratio (INR). Your INR needs to be in the correct range. To ensure that it is, your doctor may adjust your warfarin dosage now and then.
Certain medical conditions, drugs, supplements, foods, and other health factors can increase the risk of bleeding with warfarin. This article provides numerous examples. It’s important not to take certain medications, over-the-counter drugs, supplements, vitamins, or herbs along with warfarin. Before you take any while taking warfarin, ask whether your doctor recommends taking or avoiding these.
While taking warfarin, take extra care when doing activities that could lead to injury. These include using tools or knives, gardening, or participating in certain sports.
Tell your doctor if you have any unusual bruising or bleeding. This includes nosebleeds, gums that bleed, and periods that are heavier than usual. If you pass red or pink urine or black, tarry stools, call your doctor right away. Also, call 911 or your local emergency number right away if you:
- have bleeding that won’t stop
- are coughing up or vomiting blood
- have sudden and severe headache, weakness, numbness, or loss of vision
To learn more about this boxed warning, talk with your doctor.
Disclaimer: Optum Perks has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
