Medications


Warfarin tablets

What is this medicine?

WARFARIN (WAR far in) is an anticoagulant. It is used to treat or prevent clots in the veins, arteries, lungs, or heart.

How should I use this medicine?

Take this medicine by mouth with a glass of water. Follow the directions on the prescription label. You can take this medicine with or without food. Take your medicine at the same time each day. Do not take it more often than directed. Do not stop taking except on your doctor's advice. Stopping this medicine may increase your risk of a blood clot. Be sure to refill your prescription before you run out of medicine.

If your doctor or healthcare professional calls to change your dose, write down the dose and any other instructions. Always read the dose and instructions back to him or her to make sure you understand them. Tell your doctor or healthcare professional what strength of tablets you have on hand. Ask how many tablets you should take to equal your new dose. Write the date on the new instructions and keep them near your medicine. If you are told to stop taking your medicine until your next blood test, call your doctor or healthcare professional if you do not hear anything within 24 hours of the test to find out your new dose or when to restart your prior dose.

A special MedGuide will be given to you by the pharmacist with each prescription and refill. Be sure to read this information carefully each time.

Talk to your pediatrician regarding the use of this medicine in children. Special care may be needed.

What side effects may I notice from receiving this medicine?

Side effects that you should report to your doctor or health care professional as soon as possible:

  • allergic reactions like skin rash, itching or hives, swelling of the face, lips, or tongue

  • heavy menstrual bleeding or vaginal bleeding

  • painful, blue or purple toes

  • painful skin ulcers that do not go away

  • signs and symptoms of bleeding such as bloody or black, tarry stools; red or dark-brown urine; spitting up blood or brown material that looks like coffee grounds; red spots on the skin; unusual bruising or bleeding from the eye, gums, or nose

  • signs and symptoms of a blood clot such as chest pain; shortness of breath; pain, swelling, or warmth in the leg

  • signs and symptoms of a stroke such as changes in vision; confusion; trouble speaking or understanding; severe headaches; sudden numbness or weakness of the face, arm or leg; trouble walking; dizziness; loss of coordination

  • stomach pain

  • unusually weak or tired

Side effects that usually do not require medical attention (report to your doctor or health care professional if they continue or are bothersome):

  • diarrhea

  • hair loss

What may interact with this medicine?

Do not take this medicine with any of the following medications:

  • defibrotide

This medicine may also interact with the following medications:

  • acyclovir

  • allopurinol

  • aprepitant

  • armodafinil

  • aspirin

  • bicalutamide

  • bosentan

  • caffeine

  • capecitabine

  • certain antibiotics like erythromycin, clarithromycin, ciprofloxacin, cotrimoxazole, metronidazole, norfloxacin, or tigecycline

  • certain antivirals for HIV or hepatitis

  • certain medicines for blood clots like argatroban, aspirin, bivalirudin, enoxaparin, fondaparinux, heparin, or lepirudin

  • certain medicines for blood pressure, heart disease, irregular heart beat

  • certain medicines for cholesterol like atorvastatin, lovastatin, and simvastatin

  • certain medicines for depression, anxiety, or psychiatric disorders

  • certain medicines for fungal infections like fluconazole, ketoconazole, itraconazole, posaconazole, or voriconazole

  • certain medicines for seizures like carbamazepine, phenobarbital, phenytoin, rufinamide

  • cilostazol

  • clopidogrel

  • conivaptan

  • cyclosporine

  • dipyridamole

  • disulfiram

  • female hormones, including contraceptive or birth control pills

  • herbal or dietary products like garlic, ginkgo, ginseng, green tea, kava kava, red yeast rice, St. Johns Wort

  • isoniazid

  • methoxsalen

  • modafinil

  • nilotinib

  • NSAIDs, medicines for pain and inflammation, like ibuprofen or naproxen

  • oxandrolone

  • phenylpropanolamine

  • prasugrel

  • rifampin

  • steroid medicines like prednisone or cortisone

  • stomach acid blockers like cimetidine, famotidine, ranitidine, or omeprazole

  • sulfinpyrazone

  • thiabendazole

  • ticlopidine

  • vitamin K

  • zafirlukast

  • zileutin

What if I miss a dose?

It is important not to miss a dose. If you miss a dose, call your healthcare provider. Take the dose as soon as possible on the same day. If it is almost time for your next dose, take only that dose. Do not take double or extra doses to make up for a missed dose.

Where should I keep my medicine?

Keep out of the reach of children.

Store at room temperature between 15 and 30 degrees C (59 and 86 degrees F). Protect from light. Throw away any unused medicine after the expiration date. Do not flush down the toilet.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:

  • alcoholism

  • anemia

  • bleeding disorders

  • cancer

  • diabetes

  • heart disease

  • high blood pressure

  • history of bleeding in the gastrointestinal tract

  • history of stroke or other brain injury or disease

  • kidney or liver disease

  • protein C deficiency

  • protein S deficiency

  • psychosis or dementia

  • recent injury, recent or planned surgery or procedure

  • an unusual or allergic reaction to warfarin, other medicines, foods, dyes, or preservatives

  • pregnant or trying to get pregnant

  • breast-feeding

What should I watch for while using this medicine?

Visit your healthcare professional for regular checks on your progress. You will need to have a blood test called a PT/INR regularly. The PT/INR blood test is done to make sure you are getting the right dose of this medicine. It is important to not miss your appointment for the blood tests. When you first start taking this medicine, these tests are done often. Once the correct dose is determined and you take your medicine properly, these tests can be done less often.

Wear a medical ID bracelet or chain, and carry a card that describes your disease and details of your medicine and dosage times.

Do not start taking or stop taking any medicines or over-the-counter medicines except on the advice of your healthcare professional.

You should discuss your diet with your healthcare professional. Do not make major changes in your diet. Vitamin K can affect how well this medicine works. Many foods contain vitamin K. It is important to eat a consistent amount of foods with vitamin K. Other foods with vitamin K that you should eat in consistent amounts are asparagus, basil, black-eyed peas, broccoli, brussel sprouts, cabbage, green onions, green tea, parsley, green leafy vegetables like beet greens, collard greens, kale, spinach, turnip greens, or certain lettuces like green leaf or romaine.

This medicine can cause birth defects or bleeding in an unborn child. Women of childbearing age should use effective birth control while taking this medicine. If a woman becomes pregnant while taking this medicine, she should discuss the potential risks and her options with her healthcare professional.

Avoid sports and activities that might cause injury while you are using this medicine. Severe falls or injuries can cause unseen bleeding. Be careful when using sharp tools or knives. Consider using an electric razor. Take special care brushing or flossing your teeth. Report any injuries, bruising, or red spots on the skin to your healthcare professional.

If you have an illness that causes vomiting, diarrhea, or fever for more than a few days, contact your health care professional. Also, check with your healthcare professional if you are unable to eat for several days. These problems can change the effect of this medicine.

Even after you stop taking this medicine, it takes several days before your body recovers its normal ability to clot blood. Ask your healthcare professional how long you need to be careful. If you are going to have surgery or dental work, tell your health care professional that you have been taking this medicine.


NOTE:This sheet is a summary. It may not cover all possible information. If you have questions about this medicine, talk to your doctor, pharmacist, or health care provider. Copyright© 2021 Elsevier
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