Warfarin (Coumadin) is a blood thinner (anticoagulant). It's used to prevent and treat blood clots in adults and children with conditions such as deep vein thrombosis (DVT) or pulmonary embolism (PE). Warfarin (Coumadin) is taken by mouth, typically once daily. Your provider will adjust the dose based on your international normalized ratio (INR). Taking too much warfarin (Coumadin) can lead to side effects like bruising and serious bleeding. If needed, your provider can give you an antidote to reverse the effects of warfarin (Coumadin).
Prevention and treatment blood clots in the veins
Prevention and treatment blood clots linked to atrial fibrillation (AFib) or heart valve replacement
Prevention of more blood clots and to lower risk of death after a heart attack
Warfarin (Coumadin) is a blood thinner. It's also known as a vitamin K antagonist, meaning it stops vitamin K from working properly. Your body typically uses vitamin K to make blood clots. Warfarin (Coumadin) prevents blood clots from forming by blocking vitamin K.
Source:Â DailyMed
Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur:
Less common
Bleeding gums
blood in the urine
bloody stools
blurred vision
burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
chest pain or discomfort
confusion
coughing up blood
difficulty with breathing or swallowing
dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
excessive bruising
headache
increased menstrual flow or vaginal bleeding
nosebleeds
paralysis
peeling of the skin
prolonged bleeding from cuts
red or black, tarry stools
red or dark brown urine
stomach pain with cramping
sweating
unexplained swelling
unusual tiredness or weakness
Rare
Arm, back, or jaw pain
blue-green to black skin discoloration
blue or purple toes
change in consciousness
chest tightness or heaviness
chills
clay-colored stools
dizziness
fainting or loss of consciousness
fast or irregular breathing
fast or irregular heartbeat
itching or skin rash
light-colored stools
loss of appetite
pain in the toes
pain, redness, or sloughing of the skin
pale skin
purplish red, net-like, blotchy spots on the skin
skin blisters
small red or purple spots on the skin
stomach pain
swelling of the eyes or eyelids
troubled breathing with exertion
unpleasant breath odor
unusual bleeding or bruising
upper right stomach pain
vomiting of blood
yellow eyes and skin
Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Rare
Bloated
change in taste, or bad, unusual, or unpleasant (after) taste
cold intolerance
excess air or gas in the stomach or intestines
full feeling
general feeling of discomfort or illness
hair loss or thinning of the hair
hives or welts
lack or loss of strength
passing gas
red, sore, or itching skin
sores, welting, or blisters
unusual drowsiness, dullness, or feeling of sluggishness
Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.
Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.
Each strength of tablet is a unique color, making it easy to tell them apart
Only needs to be taken once a day
Has an antidote available in case of an emergency
Available as a lower-cost generic
Only prevents new blood clots from forming or getting bigger; it doesn't work on existing blood clots
Requires regular blood draws to check INR levels
Interacts with foods and many commonly-prescribed medications
Not safe to take during pregnancy
Mark your calendar with your appointments to see your provider and get any blood work done (e.g., INR, blood cell count). This will help make sure the medication is working well for you and you're not having side effects.
You can take warfarin (Coumadin) with or without food. If it's hurting your stomach, taking it with food can help.
Be consistent with the time of day you take your warfarin (Coumadin) dose as well as how much vitamin K-rich foods you eat. This will help make sure you respond to the medication well and that your INR result is where it should be. Talk to your provider if you have significant changes in your diet, health, or timing of your doses. You might need to get your INR checked sooner.
Take warfarin (Coumadin) exactly as your provider tells you. Make sure you know your prescribed warfarin (Coumadin) dose and the tablet sizes you have. It's possible you might need to take more than one strength, have to split tablets in half, or skip doses on certain days of the week. Ask your provider if you're not sure what your warfarin (Coumadin) dose is.
Warfarin (Coumadin) can make you bleed and bruise more easily. Be careful with high-impact activities or sports while taking this medication and for 5 days after your last dose. Stop taking the medication and get medical help right away if you feel lightheaded, dizzy, are vomiting or coughing up blood, or have blood in your stool. These are signs of bleeding that might be happening in your body.
Get medical help right away if you fall and hit your head, especially if you feel dizzy or have a headache. Your provider will want to check to make sure you don't have any brain bleeds.
If you're going to have a dental procedure or surgery, make sure your dentist or surgeon knows you're taking warfarin (Coumadin) and which provider prescribed it for you. You might have to temporarily stop your warfarin (Coumadin) a few days before the procedure.
Warfarin (Coumadin) can interact with many medications and supplements. Make sure your provider knows which medications you're taking, especially if you're taking a medication that can cause bleeding or supplements containing vitamin K. They might want to check your INR more often after you start anything new.
Warfarin (Coumadin) can cause some serious health issues. This risk may be even higher for certain groups. If this worries you, talk to your doctor or pharmacist about other options.
Risk factors: Higher-than-recommended INR | Age greater than 65 years | Bleeding problems or injury | High blood pressure | Kidney or liver problems | Cancer | Taking other medications that raise your risk for bleeding | Drinking alcohol
Taking warfarin (Coumadin) can raise your risk for bleeds. Your provider will check your INR regularly to make sure it's within a safe range. Keep in mind that other medications and foods can interact with warfarin (Coumadin) and affect how well it works. Your provider might check your INR more often any time you start or stop a medication, or make changes to your diet.
Get immediate medical attention if you fall and hit your head so your care team can check for signs of bleeding on the inside of your body. Also, get help right away if you notice blood in your urine, have bright red or dark, tarry "coffee ground" stool, cough or vomit blood, or can't stop bleeding from a wound.
If you do have a serious bleed, your provider will give you prothrombin complex concentrate (Kcentra, Balfaxar) and vitamin K (phytonadione) to reverse the effects of warfarin (Coumadin).
Don't skip doses or suddenly stop taking warfarin (Coumadin) unless your provider specifically told you it's safe to do so. This raises your risk of blood clots to form in your body. If you're wanting to stop warfarin (Coumadin), contact your provider so they can create a safe plan for you. Go to the hospital if you experience symptoms of blood clots, such as:
- Stroke: sudden numbness or weakness on one side of the body, feeling confused, trouble speaking or understanding speech, dizziness, trouble keeping balance
- Blood clot in the leg or arm: swelling or redness in arms or legs, skin that's warm to touch
- Blood clot in the lungs: trouble breathing, chest pain, cough, irregular heartbeat
Taking warfarin (Coumadin) can raise your risk of clots made of fat to be released into your blood. Like blood clots, they can get trapped into smaller blood vessels and stop blood flow to important organs. The most commonly involved organs are the kidneys, pancreas, spleen, and liver. It can also happen in your feet, which can cause your toes to turn a dark purple or blue color (a problem called "purple toe syndrome"). If you notice any skin color changes after starting warfarin (Coumadin), talk to your provider right away, as you'll need to stop the medication.
Although rare, warfarin (Coumadin) can cause a potentially serious and life-threatening condition called calciphylaxis. This is when calcium builds up in the blood vessels. When this happens, there's less room for blood to flow through your vessels. Symptoms include skin discoloration, skin sores, painful lumps in the skin, or skin infections. Seek medical help right away if you notice any significant skin changes while taking warfarin (Coumadin).
Risk factors: Use in people with heparin-induced thrombocytopenia (HIT) or HIT with thrombosis syndrome (HITTS)
Although rare, taking warfarin (Coumadin) can cause blood flow problems to the skin, which can lead to skin tissue death (called necrosis) and gangrene. This side effect has been reported as early as within a few days of starting warfarin (Coumadin). While the cause isn't clear, it's likely related to clotting problems.
This side effect can also happen in people with heparin-induced thrombocytopenia (HIT), which is a severe reaction to heparin.
Seek medical help right away if you notice skin discoloration (especially darkened skin color), swelling, blisters, sudden and severe pain in skin, numbness. Your provider will likely ask you to stop taking warfarin (Coumadin).
Warfarin (Coumadin) can cause birth defects and severe harm to babies and mothers. This medication shouldn't be used in pregnancy unless the benefit is clearly greater than the risk, such as in people who are at high risk for clots. Your provider might test you for pregnancy before starting warfarin (Coumadin). If you're able to become pregnant, use birth control (contraception) during, and for at least one month after, stopping warfarin (Coumadin). Talk to your provider right away if you become pregnant or are thinking of becoming pregnant.
The typical starting dose ranges from 2 mg to 5 mg by mouth once daily. Your provider will adjust the dose based on your international normalized ratio (INR). The usual maintenance dose of warfarin (Coumadin) ranges from 2 mg to 10 mg once daily.
Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.
Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Using this medicine with any of the following medicines may cause an increased risk of certain side effects, but using both drugs may be the best treatment for you. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.
Pregnancy (except for those with artificial heart valves who are at risk for clots)
Abortion or pregnancy complications (e.g., eclampsia or pre-eclampsia)
Active bleeding, easily bleed, or bleeding problems
Recent surgery, or having surgery soon, in the brain, spinal cord, eye, or trauma surgery that requires large open surfaces
Inability to be consistent with taking warfarin (Coumadin)
Spinal puncture, or other procedures with potential to cause uncontrolled bleeding
Major regional or lumbar block anesthesia
Severely high blood pressure (malignant hypertension)
Prevention and treatment blood clots in the veins
Prevention and treatment blood clots linked to atrial fibrillation (AFib) or heart valve replacement
Prevention of more blood clots and to lower risk of death after a heart attack
Lower the risk of stroke or blood clots in people with atrial fibrillation (AFib) not caused by a heart valve problem
Treat blood clots in the legs (deep vein thrombosis (DVT)) or lungs (pulmonary embolism (PE))
Lower the risk of DVT or PE coming back after treatment
Treat blood clots and lower the risk of new clots in children from birth and older
Lower the risk of stroke and blood clots in people with atrial fibrillation (AFib) not caused by a heart valve problem
Treat blood clots in the legs (deep vein thrombosis (DVT)) or lungs (pulmonary embolism (PE))
Lower the risk of DVT or PE coming back after treatment
Prevent blood clots in people in the hospital or recently released who are at high risk
Lower the risk of serious heart problems, like heart attack or stroke, in people with coronary artery disease (CAD), taken with aspirin
Lower the risk of blood clots and related problems in people with peripheral artery disease (PAD), taken with aspirin
Treat blood clots and lower the risk of new clots in children from birth to under 18 years old
Prevent blood clots in children 2 years and older with congenital heart disease (CHD) after a Fontan procedure
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Buttolph, A., et al. (2023). Gangrene. StatPearls.
Garrison, S. R., et al. (2020). The effect of warfarin administration time on anticoagulation stability (INRange): A pragmatic randomized controlled trial. Annals of Family Medicine.
Naranjo, M., et al. (2023). Malignant hypertension. StatPearls.
National Institutes of Health, Office of Dietary Supplements. (2021). Vitamin K: Fact sheet for health professionals.
Patel, S., et al. (2023). Warfarin. StatPearls.
Scrinivasan, A. F., et al. (2004). Warfarin-induced skin necrosis and venous limb gangrene in the setting of heparin-induced thrombocytopenia. Archives of Internal Medicine.
Upsher-Smith Laboratories, LLC. (2023). Jantoven- warfarin sodium tablet [package insert]. DailyMed.
Westphal, S. G., et al. (2023). Calciphylaxis. StatPearls.
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