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Warfarin, Oral Tablet

Highlights for warfarin

  1. Warfarin oral tablet is available as both a generic and brand-name drug. Brand name: Coumadin.
  2. Side effects are often related to abnormal bleeding. These include bruising easily, nosebleeds, bleeding from your gums, bleeding from cuts that takes a long time to stop, and heavier than normal menstrual bleeding.
  3. Warfarin is used to treat and prevent blood clots that might result in heart attack, stroke, or death. It’s also used for blood clots in atrial fibrillation, heart valve replacement, venous thrombosis, and pulmonary embolism.
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Important warnings

Important warnings

FDA Warning: Bleeding risk
  • This drug has a Black Box Warning. This is the most serious warning from the Food and Drug Administration (FDA). A black box warning alerts doctors and patients to potentially dangerous effects.
  • Warfarin thins your blood and limits your blood’s ability to clot. It can cause serious bleeding, which can lead to death. You must have regular blood tests and visits with your doctor to monitor your condition. Don’t start or stop any other drug or herbal product unless your doctor tells you to. Tell your doctor if you have any signs or symptoms of bleeding.

Bleeding problems warning: Tell your doctor if you have an increased risk of bleeding problems, such as being at least 65 years of age, having a history of heart attack or stroke, gastrointestinal bleeding, anemia, diabetes, or kidney problems. Your doctor will decide if warfarin is right for you.

Pregnancy warning: Don’t take this medication if you’re pregnant unless you have a mechanical heart valve. Warfarin may cause birth defects, miscarriage, or death of a fetus.

Calciphylaxis warning: This medication can cause calciphylaxis. This rare but serious condition is a buildup of calcium in small blood vessels. People with kidney disease are at greater risk for this condition.

About

What is warfarin?

Warfarin oral tablet is a prescription drug that’s available as the brand-name drug Coumadin. It’s also available as a generic drug. Generic drugs usually cost less. In some cases, they may not be available in every strength or form as the brand.

Why it's used

Warfarin is used to treat blood clots and to lower the chance of blood clots forming in your body. Blood clots can cause a stroke, heart attack, or other serious conditions if they form in your legs or lungs.

Warfarin is approved for:

  • the reduction of risk of heart attack, stroke, or death
  • prevention and treatment of clots with atrial fibrillation or heart valve replacement
  • prevention and treatment of clots in the lower body and in the lungs

This drug may be used as part of a combination therapy. That means you may need to take it with other drugs.

How it works

Warfarin works by stopping your body from forming blood clots. It does this by blocking the formation of blood clotting factors, which are needed to make clots.

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Side effects

Warfarin side effects

Warfarin oral tablet doesn’t cause drowsiness. However, it can cause other side effects.

More common side effects

The more common side effects that occur with warfarin are related to abnormal bleeding. Possible side effects include:

  • unusual bruising, such as:
    • unexplainable bruises
    • bruises that grow in size
  • nosebleeds
  • bleeding gums
  • bleeding from cuts that takes a long time to stop
  • heavier than normal menstrual or vaginal bleeding
  • pink or brown urine
  • red or black stools
  • coughing up blood
  • vomiting blood or materials that looks like coffee grounds

Serious side effects

If you experience any of these serious side effects, call your doctor right away. If your symptoms are potentially life threatening, or if you think you’re experiencing a medical emergency, call 911.

  • death of skin tissue. This may happen when blood clots form and block blood flow to an area of your body. Symptoms may include:
    • pain
    • color or temperature change to any area of your body
  • purple toes syndrome. Symptoms may include:
    • pain and purple or dark color in your toes

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.

Interactions

Warfarin may interact with other medications

Warfarin oral tablet can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well.

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Examples of drugs that can cause interactions with warfarin are listed below.

Anticoagulants

Your risk of bleeding is increased when you take warfarin with anticoagulants. Examples are:

  • Factor Xa inhibitors
    • apixaban
    • edoxaban
    • rivaroxaban
  • Direct thrombin inhibitors
    • dabigatran

Antiplatelet drugs

Your risk of bleeding is increased when you take warfarin with antiplatelet drugs. Examples are:

  • P2Y12 platelet inhibitors
    • clopidogrel
    • prasugrel
    • ticagrelor

Nonsteroidal anti-inflammatory drugs (NSAIDs)

Your risk of bleeding is increased when you take warfarin with NSAIDs. Examples are:

  • diclofenac
  • ibuprofen
  • indomethacin
  • ketoprofen
  • ketorolac
  • meloxicam
  • nabumetone
  • naproxen
  • oxaprozin
  • piroxicam

Antidepressants

Your risk of bleeding is increased when you take warfarin with selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs). Examples are:

  • SSRIs:
    • citalopram
    • dapoxetine
    • escitalopram
    • fluoxetine
    • fluvoxamine
    • paroxetine
    • sertraline
    • vilazodone
    • vortioxetine
  • SNRIs:
    • duloxetine
    • venlafaxine

Antibiotics and antifungals

Some antibiotics and antifungals can change how warfarin works in your body. Your doctor may monitor you more closely when you start or stop an antibiotic or antifungal medication. Examples are:

  • Antibiotics
    • Macrolides:
      • azithromycin
      • clarithromycin
      • erythromycin
    • Sulfamethoxazole/trimethoprim
  • Antifungals
    • Azole antifungals
      • fluconazole
      • itraconazole
      • ketoconazole
      • posaconazole
      • voriconazole

Herbal products

Some herbal products may increase the blood thinning effect of warfarin. Examples are:

  • garlic
  • ginkgo biloba

Some herbal products may decrease the effects of warfarin and increase your risk of blood clots. Examples are:

  • coenzyme Q10
  • St. John’s wort
  • ginseng

Drugs that affect CYP450 enzyme

CYP450 enzyme helps your body to break down and process medications. Drugs that affect this enzyme may affect how your body handles warfarin.

Certain medications and herbs can increase the amount of warfarin in your body. This can put you at a higher risk of bleeding. Examples are:

  • amiodarone
  • efavirenz
  • isoniazid
  • metronidazole
  • paroxetine
  • sulfamethoxazole
  • voriconazole

Certain medications and herbs can make CYP450 work faster. This can lower the amount of warfarin and put you at a higher risk of blood clots. Examples are:

  • carbamazepine
  • nevirapine
  • phenobarbital
  • rifampin
  • St. John’s wort

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.

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Other warnings

Warfarin warnings

Warfarin oral tablet comes with several warnings.

Allergy warning

Warfarin can cause a severe allergic reaction. Symptoms may include:

  • trouble breathing
  • swelling of your throat or tongue
  • hives

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal.

Food Interactions

Some foods and beverages can interact with warfarin and affect your treatment and dose.

Eat a normal, balanced diet. Talk to your healthcare provider before you make any diet changes. Don’t eat large amounts of leafy, green vegetables. Leafy, green vegetables contain vitamin K. Certain vegetable oils also contain large amounts of vitamin K. Too much vitamin K can reduce the effect of warfarin.

Warnings for people with certain health conditions

For people with high blood pressure: You may have a higher risk of bleeding if you take warfarin.

For people with history of gastrointestinal bleeding: If you have a history of stomach or intestinal bleeding, warfarin may increase your risk of bleeding.

For people with heart disease or stroke: If you have heart disease or a history of stroke, your blood vessels may already be damaged and can easily bleed. Warfarin may increase your risk of bleeding.

For people with low blood count or cancer: Some cancers can cause internal bleeding. You may have a higher risk of bleeding if you take warfarin.

For people who have had head trauma: Warfarin thins your blood. This makes it harder for your blood to clot when you’re bleeding. You may have a higher risk of bleeding if you take warfarin.

For people with kidney problems: If you have a history of kidney disease, warfarin increases your risk of serious kidney damage. In addition, you have a higher bleeding risk when taking warfarin. For both of these reasons, your doctor will likely monitor your INR (international normalized ratio) closely to check how your blood is clotting.

Warnings for other groups

For pregnant women: Warfarin is a category X pregnancy drug. Category X drugs should never be used during pregnancy.

Warfarin is a category D pregnancy drug if you have a mechanical heart valve. Warfarin may cause harm to the fetus when given to a pregnant woman. However, patients with heart valve disease are already at a higher risk for getting a clot. This can harm both the mother and the baby.

Tell your doctor if you’re pregnant or plan to become pregnant. Warfarin should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Women who are breastfeeding: Warfarin may pass through breast milk. You and your doctor may decide if you’ll take warfarin or breastfeed.

For seniors: If you are over 60 years of age, you may be more sensitive to warfarin. Your doctor may give you a lower warfarin dose.

For children: The effectiveness and safety of warfarin haven’t been established in people younger than 18 years old.

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Dosage

How to take warfarin

This dosage information is for warfarin oral tablet. All possible dosages and forms may not be included here. Your dose, form, and how often you take it will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

Forms and strengths

Generic: warfarin

  • Form: Oral tablet
  • Strengths: 1 mg, 2 mg, 2.5 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7.5 mg, and 10 mg

Brand: Coumadin

  • Form: Oral tablet
  • Strengths: 1 mg, 2 mg, 2.5 mg, 3 mg, 4 mg, 5 mg, 6 mg, 7.5 mg, and 10 mg

Dosage for reduction in the risk of death, another heart attack, or stroke

Adult dosage (ages 18 and older)

Your dose of warfarin sodium is based on your prothrombin time (PT)/international normalized ration (INR) blood test. The typical starting dose is 5 mg to 10 mg once per day. Your dose may change over time based on your test and your condition.

Child dosage (ages 0-17 years)

A safe and effective dosage hasn’t been established for this age group.

Dosage for prevention and treatment of clots with atrial fibrillation or heart valve replacement

Adult dosage (ages 18 and older)

Your dose of warfarin sodium is based on your prothrombin time (PT)/international normalized ration (INR) blood test. The typical starting dose is 5 mg to 10 mg once per day. Your dose may change over time based on your test and your condition.

Child dosage (ages 0-17 years)

A safe and effective dosage hasn’t been established for this age group.

Dosage for prevention and treatment of clots in the lower body and in the lungs

Adult dosage (ages 18 and older)

Your dose of warfarin sodium is based on your prothrombin time (PT)/international normalized ration (INR) blood test. The typical starting dose is 5 mg to 10 mg once per day. Your dose may change over time based on your test and your condition.

Child dosage (ages 0-17 years)

A safe and effective dosage hasn’t been established for this age group.

Special Considerations

  • If you’re over 60 years of age, you may be more sensitive to warfarin. Your doctor may give you a lower warfarin dose.
  • People of Asian descent usually respond to a lower dose of warfarin. Your doctor may give you a lower dose.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.

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Take as directed

Take as directed

Warfarin may be a short-term or long-term drug treatment. How long you take this medication depends on the nature of your condition. It comes with risks if you don’t take it as prescribed.

If you skip or miss doses: Stopping or missing doses can cause complications, such as heart attack, stroke, or blood clots in your veins or lungs. Taking your medication as directed by your doctor, even when you’re feeling well, will give you the best chance of not having the complications.

If you take too much: Taking too much warfarin can lead to life-threatening bleeding. If you take too much, call your doctor or go to the nearest hospital emergency room right away.

What to do if you miss a dose: If you miss a dose, take it as soon as you can. Skip the missed dose if it’s almost time for your next scheduled dose. Don’t use extra medicine to make up the missed dose. This could result in toxic side effects.

How to tell if the drug is working: You may not feel any different if warfarin is working. However, you may notice reduced bleeding. Your doctor will do blood tests to see how well the drug is working.

Important considerations

Important considerations for taking warfarin

Keep these considerations in mind if your doctor prescribes warfarin oral tablet for you.

General

Warfarin tablets may be split during therapy. Talk to your healthcare provider to find available pill cutters/splitters.

Storage

  • Store in temperatures from 68–77°F (20–25°C).
  • Don’t freeze warfarin.
  • Keep it away from light and high temperature.
  • Keep your drugs away from areas where they could get wet, such as bathrooms.

Refills

A prescription for this medication is refillable. You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry it with you or in your carry-on bag.
  • Don’t worry about airport X-ray machines. They can’t hurt this medication.
  • You may need to show your pharmacy’s preprinted label to identify the medication. Keep the original prescription-labeled box with you when traveling.

Clinical monitoring

You must have regular blood tests and visits with your doctor to monitor your condition. Make sure you don’t miss your appointments because your doctor determines your warfarin dose based on your blood tests.

Your diet

Some foods and beverages can interact with warfarin and affect your treatment and dose. Eat a normal, balanced diet. Talk to your healthcare provider before you make any diet changes. Don’t eat large amounts of leafy, green vegetables. Leafy, green vegetables contain vitamin K. Certain vegetable oils also contain large amounts of vitamin K. Too much vitamin K can lower the effect of warfarin.

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Alternatives

Are there any alternatives?

There are other drugs available to treat your condition. Some may be more suitable for you than others. Talk to your doctor about possible alternatives.

Disclaimer: Healthline 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 other 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.

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