• Basic Info
• Top Questions
• Clinical Info
• Interactions

What is warfarin?
Warfarin is an anticoagulant (blood thinner). Warfarin reduces the formation of blood clots. Warfarin is used to prevent heart attacks, strokes, and blood clots in veins and arteries. Warfarin may also be used for purposes other than those listed in this medication guide.

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What is the price of this medication and similar alternatives?

This pricing information is subject to change at the sole discretion of DS Pharmacy. For the most current and up-to-date pricing information, please visit drugstore.com.

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What are the possible side effects of warfarin?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

• skin changes or discoloration anywhere on your body;

• purple toes or fingers;

• pain in your stomach, back, or sides;

• low fever, loss of appetite, dark urine, jaundice (yellowing of the skin or eyes);

• diarrhea, fever, chills, body aches, flu symptoms;

• easy bruising or bleeding that will not stop;

• blood in your urine;

• black, bloody, or tarry stools;

• nosebleeds, bleeding gums, coughing up blood;

• feeling weak or light-headed;

• sudden headache, confusion, problems with vision, speech, or balance;

• sudden leg or foot pain; or

• sudden numbness or weakness, especially on one side of the body.

Less serious side effects may include:

• nausea, vomiting, stomach pain;

• gas and bloating; or

• hair loss.

This is not a complete list of side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

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How should I take warfarin?
Take this medication exactly as it was prescribed for you. Do not take the medication in larger amounts, or take it for longer than recommended by your doctor. Your doctor may occasionally change your dose to make sure you get the best results from this medication. Follow the directions on your prescription label. Take each dose with a full glass of water. Take warfarin at the same time every day. Warfarin can be taken with or without food. Your body's response to warfarin can be affected by your diet, environment, physical well-being, and other medicines or herbal (botanical) products you use.

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What is the most important information I should know about warfarin?
This medication can cause birth defects in an unborn baby. Do not use if you are pregnant. Use an effective form of birth control, and tell your doctor if you become pregnant during treatment. Never take a double dose of this medication. If you need to have a lumbar puncture (spinal tap) or any type of surgery, you may need to temporarily stop using warfarin. Be sure the surgeon knows ahead of time that you are using this medication. Carry an ID card or wear a medical alert bracelet stating that you are taking warfarin, in case of emergency. Any doctor, dentist, or emergency medical care provider who treats you should know that you are taking warfarin.

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What happens if I miss a dose?
Take the missed dose as soon as you remember, and call your doctor as soon as possible. You may take two doses on the same day, but do not take two doses at the same time.

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What other drugs will affect warfarin?
Warfarin interacts with many other drugs, and these interactions can be dangerous, even fatal. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor. Keep a list with you of all the medicines you use and show this list to any doctor or other healthcare provider who treats you. Warfarin can interact with the following herbal (botanical) products:

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Can I take this if I am pregnant or trying to get pregnant or if I am breastfeeding?

Warfarin has been assigned to pregnancy category X by the FDA. Problems associated with perinatal administration of warfarin have included central nervous system defects, spontaneous abortion, stillbirth, prematurity, hemorrhage, and ocular defects when given anytime during pregnancy, and a fetal warfarin syndrome when given during the first trimester. Warfarin is considered contraindicated during pregnancy.

Limited data suggest warfarin fetal complications may be dose dependent. A study of 58 pregnancies with 31 healthy babies revealed an increased incidence of complications at dosages greater than 5 mg daily. Fetal warfarin syndrome is characterized by nasal hypoplasia, hypoplasia of the extremities, and developmental retardation. In a review of 418 reported pregnancies during which warfarin was administered, one-sixth resulted in fetal abnormalities, one-sixth resulted in abortion or stillbirths, and two-thirds resulted in normal infants. Nasal hypoplasia, varying in severity, is the most common feature of warfarin embryopathy. Epiphyseal stippling, primarily in the axial skeleton, proximal femurs, and the calcanei is present in the majority of cases. In addition, hypoplasia of the extremities, low birth weight, eye abnormalities (i.e. optic atrophy, microphthalmia, and blindness), and developmental retardation may be present. In one review, the common time of exposure was from the sixth to the ninth week of gestation in all 24 cases of warfarin embryopathy. Central nervous system abnormalities include dorsal midline dysplasia with agenesis of the corpus callosum, Dandy-Walker malformation, midline cerebellar atrophy, and ventral midline dysplasia with optic atrophy. Exposure time does not appear to play a role in the development of CNS anomalies. Cases have been reported in the absence of first trimester exposure. However, in one review, all cases of CNS anomalies involved second and/or third trimester exposure. Hall, et al (1980) reviewed and analyzed published cases involving coumarin use during pregnancy. A total of 418 pregnancies were evaluated. In 156 pregnancies, coumarin derivatives were used throughout pregnancy. Of these, 76% resulted in normal liveborn infants. Fetal complications, including spontaneous abortion, stillbirth, prematurity, CNS anomalies, embryopathy, and fetal hemorrhage, occurred in the remaining 24% of cases. In another literature review, Ginsberg and Hirsh (1989) documented 45 cases of warfarin embryopathy and 26 cases of CNS abnormalities out of 970 pregnancies in which warfarin was used. After excluding pregnancies with maternal comorbid conditions, analysis of cases in which oral anticoagulants were used alone revealed a 26.5% incidence of adverse pregnancy outcome. Again, use of warfarin between weeks six and twelve of gestation appeared to be associated with warfarin embryopathy. Forty-three women with mechanical heart valves, maintained throughout pregnancy on warfarin, and carrying out 58 pregnancies were observed. In the group of 25 pregnancies taking greater than 5 mg warfarin daily, 22 fetal complications and 3 full term pregnancies occurred. Complications included 18 spontaneous abortions, 2 warfarin embryopathies (spontaneously aborted in the 6 month), 1 stillbirth, and 1 ventricular septal defect (closed in the first year of life). The group of 33 pregnancies receiving less than 5 mg warfarin daily delivered 27 full term babies and 1 premature baby. Five fetal complications in this group included 4 spontaneous abortions and 1 infant with growth retardation (no skeletal, mental, or neurologic retardation, and now fully developed).

Based on limited data, warfarin has not been detected in human milk. However, changes in prothrombin time in breast-feeding infants of mothers treated with warfarin have been reported. The manufacturer recommends that caution be used when administering warfarin to nursing women.

Orme, et al (1977) evaluated the excretion of warfarin into breast milk of 13 women treated with warfarin 5 to 12 mg per day. Warfarin was undetectable (< 0.08 mmol/L) in all milk samples. Seven women elected to continue breast-feeding their infants. Warfarin was undetectable in plasma samples from all seven infants. In addition, all seven infants had normal prothrombin times. McKenna, et al (1983) reported similar results. Two women who required warfarin anticoagulation after delivery and their infants were followed, in one case for 56 days and in the other for 131 days. Both women elected to continue to breast-feed. At no time was warfarin detected in the milk of either mother nor were any changes in prothrombin activity in either infant.

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Who should NOT use this medication?

• Pregnancy.
• Bleeding, hemorrhagic blood dyscrasias (e.g., hemophilia, polycythemia vera, purpura, leukemia) or a history of hemorrhagic diathesis or tendencies.
• Recent or contemplated eye, brain, or spinal cord surgery or prostatectomy.
• Open ulcerative, traumatic, or surgical wounds.
• Active ulceration of the GI, respiratory, or GU tracts.
• Cerebrovascular hemorrhage.
• Aneurysms (cerebral, dissecting aorta).
• Pericarditis and pericardial effusions.
• Bacterial endocarditis.
• Eclampsia, preeclampsia, or threatened abortion.
• Spinal puncture or other diagnostic or therapeutic procedures with potential for uncontrolled bleeding.
• Major regional or lumbar block anesthesia.
• Severe, uncontrolled, or malignant hypertension.
• Unsupervised patients with senility, alcoholism, or psychosis.
• Known hypersensitivity to warfarin or any ingredient in the formulation.

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What happens if I overdose?
Seek emergency medical attention if you think you have used too much of this medicine. Overdose symptoms may include bruising, broken blood vessels under the skin, excessive bleeding from cuts or wounds, blood in the urine or stools, and heavy menstrual periods in women.

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What should I discuss with my healthcare provider before taking warfarin?
Do not take this medicine if you have: a bleeding disorder such as hemophilia; a blood cell disorder such as anemia; a stomach ulcer or bleeding in the stomach; a history of aneurysm, blood clot, or bleeding in your brain; or an infection of your heart, fluid or swelling around your heart. FDA pregnancy category X. This medication can cause miscarriage, stillbirth, birth defects, or fatal bleeding in an unborn baby. Do not use warfarin if you are pregnant. Tell your doctor right away if you become pregnant during treatment. Use an effective form of birth control while you are using this medication.

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Can I stop taking the medication if I feel better?
As a general rule, you should always take your medications exactly as prescribed and do not change the dosage or stop taking the medication without first discussing it with your healthcare provider.

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I am on so many medications; do I have to take them all?
This is called polypharmacy—many different medications being used at the same time by one person. Sometimes, being on multiple medications is acceptable and appropriate but at other times it may be problematic. If you are receiving your medications from multiple physicians you need to ensure that they all know what medications you are taking. The best way to do this is to make a list of all the medications you are currently using, including all nutritional supplements, homeopathic remedies, vitamins and over-the-counter drugs (if possible, also include all the diseases you have been diagnosed with). Give a copy to every doctor who takes care of you so they have it on file, this way they can avoid duplicating medications and perhaps even try to consolidate some. After every doctor's visit remember to update the list accordingly. Also, as much as you possibly can, try to use the same pharmacy to fill all your prescriptions, this way any potential drug interactions can be caught and averted.

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Where can I get more information?
More Information

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