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What is Warfarin (coumadin)?
Warfarin is an anticoagulant medication that works by inhibiting vitamin K-dependent clotting factors. It is a commonly prescribed medication for people who are at risk of developing blood clots, stroke, or heart attack due to various medical conditions.
Warfarin belongs to the drug class, anticoagulants also known as blood thinners. These medications work by preventing the formation of blood clots or reducing the size of existing blood clots.
What are the Indications for Warfarin?
Warfarin is indicated for the prevention and treatment of blood clots for patients with atrial fibrillation, which is an irregular heartbeat that can lead to blood clots forming in the heart. These clots can then travel to the brain, causing a stroke.
Warfarin is also used to prevent and treat DVT and PE, which are both conditions in which blood clots form in the veins, typically in the legs. If left untreated, these clots can break off and travel to the lungs, causing a PE, which can be life-threatening.
Warfarin is indicated for those who have undergone heart valve replacement surgery. Heart valves are important structures that help regulate blood flow in the heart, and if they are damaged, they can be replaced with mechanical or biological valves. Patients who have undergone this type of surgery are at an increased risk of developing blood clots, and warfarin can help prevent these clots from forming.
How is Warfarin used?
Warfarin should be stored at room temperature between 59° – 86°F(15° – 30°) in a tightly closed container, away from heat, light, and moisture.
Keep out of reach of children and pets.
Take warfarin by mouth, once daily, with or without food as directed by your doctor. It’s important to take Warfarin at the same time each day.
Warfarin is available in tablet form in the following strengths:
The recommended starting dose of Warfarin ranges from 2mg to 5mg daily. The maintenance dosing will be adjusted and can fluctuate based on your condition and INR results.
It’s important to understand that although Warfarin is FDA-approved, it comes with side effects that may or may not affect you.
Before starting Warfarin, you should discuss possible side effects with your doctor or pharmacist.
Common Side Effects
Not all side effects require medical attention. As your body adjusts to Warfarin, side effects may go away.
Tell your doctor if you experience the following symptoms, and they become severe or do not go away on their own:
- Bruising or bleeding easily
- Bleeding gums
- Blood in urine or stool
- Heavy menstrual bleeding
Serious Side Effects
Severe adverse reactions while using Warfarin can occur. Seek emergency medical care or call 911 if you experience any of the following symptoms:
- Severe allergic reaction: severe rash or itching, swelling in the face, lips, tongue, or throat, rapid heartbeat, fainting or dizziness, or problems breathing or swallowing.
- Excessive bleeding or hemorrhage: severe bruising, blood in the urine or stool, and prolonged bleeding from cuts or wounds.
- Skin necrosis
- Purple toe syndrome
The information above does not list all possible side effects. Contact your doctor or pharmacist if you experience any side effects not listed. You or your doctor may report side effects to the FDA by calling 1-800-FDA-1088.
Warnings & Precautions
Before using Warfarin, tell your doctor or pharmacist:
- If you are allergic to any medications such as Warfarin
- If you have high blood pressure
- If you have diabetes
- If you will be undergoing surgery or have recently had surgery
- If you will be undergoing a spinal tap or epidural
- If you have liver, kidney, or heart problems
- If you have a medical condition that makes you more likely to bleed such as ulcers or a blood cell disorder
- If you are pregnant or expect to become pregnant
- If you are breastfeeding or plan to breastfeed
Taking Warfarin can increase your risk of hemorrhage. Warfarin thins the blood to prevent clots, but too much warfarin can cause bleeding. Other risk factors in addition to taking Warfarin can also increase your chance of hemorrhage including if you are 65 years of age or older, have high blood pressure, anemia, gastrointestinal bleeding. Your doctor will regularly monitor your INR to adjust your dose, as needed.
Death of Skin Tissue (Necrosis)
Taking warfarin can cause tissue necrosis, or death of body tissue, because it can reduce blood flow to certain areas of the body. If blood flow is reduced too much, the tissue may not receive enough oxygen and nutrients, leading to tissue death. Symptoms of tissue necrosis may occur suddenly or develop gradually over time.
Symptoms in the affected area include pain or discomfort, swelling, redness, skin discoloration, blistering or skin breakdown, ulcers or sores that do not heal, and numbness or tingling. Contact your doctor right away if you experience any of these symptoms while taking Warfarin.
Purple Toe Syndrome
Taking warfarin can cause purple toe syndrome, a rare condition where the toes or other parts of the foot turn purple and painful due to blood vessel damage. Warfarin can cause a decrease in the levels of proteins that help to prevent blood clots from forming in the small blood vessels in the feet. This can lead to blood clots, which can then cause purple toe syndrome. If you experience sudden or severe pain in your toes or other parts of your foot while taking warfarin, seek medical care right away.
Pregnant or Planning to Become Pregnant
Taking Warfarin during pregnancy can severely harm your unborn child resulting in birth defects and may increase your risk of bleeding. If you are pregnant or become pregnant while taking Warfarin, contact your doctor immediately.
It is not known if Warfarin passes into breast milk. If you are breastfeeding or considering breastfeeding while taking Warfarin, talk to your doctor for the best course of action before taking Warfarin.
Interactions & Contraindications
Before using Warfarin, tell your doctor or pharmacist if you take any medications, herbal supplements, or vitamins.
Warfarin is metabolized by an enzyme called CYP450 in the liver. Some medications can affect the activity of CYP450 and change the way warfarin is metabolized, which can lead to an increased or decreased effect of warfarin. Drugs that increase the activity of CYP450 can make warfarin less effective and increase the risk of blood clots, while drugs that decrease the activity of CYP450 can make warfarin more potent and increase the risk of bleeding. Consult with your doctor to determine if any of the medications you are taking will interact with Warfarin.
Non-steroid Anti-inflammatory Drugs (NSAID)
Taking Warfarin with NSAIDs can increase your risk of bleeding. NSAIDs can interfere with your blood’s ability to clot and increase the effects of warfarin, leading to bleeding. The risk of bleeding may be higher in people who are elderly, have kidney disease, or take higher doses of NSAIDs.
Taking warfarin along with other anticoagulant medications can increase the risk of bleeding. Anticoagulants are medications that also help to prevent blood clots from forming in the body, and taking them together with warfarin can increase the effects of both drugs. This can lead to bleeding complications such as bruising, nosebleeds, or bleeding in the gastrointestinal tract.
Serotonin Reuptake Inhibitors (SSRI)
Taking warfarin with serotonin reuptake inhibitor (SSRI) medications can increase your risk of bleeding. SSRIs are commonly used to treat depression and anxiety, and they can interfere with the way warfarin is metabolized in your body. This can cause an increased effect of warfarin, leading to a higher risk of bleeding. If you experience any symptoms of bleeding, such as easy bruising or nosebleeds, contact your doctor right away.
Antibiotics and Antifungals
Some antibiotics and antifungal medications can interact with warfarin and increase your risk of bleeding. These medications can interfere with the way warfarin is metabolized in the body, leading to an increased effect of warfarin and a higher risk of bleeding. Your doctor may need to adjust your dose or change your medication to avoid potential complications.
Food and Grapefruit
Some foods such as grapefruit can interact with warfarin and increase your risk of bleeding. These foods contain compounds that can interfere with the way warfarin is metabolized in the body, leading to an increased effect of warfarin and a higher risk of bleeding. Consult with your doctor on what food should be avoided while taking warfarin.