Author: Charles Frank

Warfarin Oral: Uses, Side Effects, Interactions, Pictures, Warnings & Dosing

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. Warfarin belongs to a class of drugs called anticoagulants. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

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. Changing your eating habits may mean that you’ll be getting more or less vitamin K in the foods you eat.

International Patients

Tell your doctor if you are pregnant or plan to become pregnant. Your doctor should order a pregnancy test before you start this medication. Ask about reliable forms of birth control while using this medication and for at least 1 month after the last dose. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication. If you are planning pregnancy, discuss a plan for managing your condition with your doctor before you become pregnant. Your doctor may switch the type of medication you use during pregnancy.

If your doctor tells you to stop taking warfarin, the effects of this medication may last for 2 to 5 days after you stop taking it. Some people may respond differently to warfarin based on their heredity or genetic make-up. Your doctor may order a blood test to help find the dose of warfarin that is best for you. Changes to diet, starting or stopping other drugs, and certain lifestyle choices, such as alcohol intake or cigarette smoking, can alter a patient’s INR. Tell your doctor if you’re pregnant or plan to become pregnant.

Tell your doctor if you are sick with diarrhea, fever, chills, or flu symptoms, or if your body weight changes. Warfarin activity is determined partially by genetic factors. Polymorphisms in two genes (VKORC1 and CYP2C9) play a particularly large role in response to warfarin.

1. While your provider is waiting for warfarin to kick in, they’ll sometimes give you a different anticoagulant, usually injectable, that works right away.
2. However, consult your doctor or pharmacist before switching warfarin products.
3. The interactions with warfarin usually result in an increase or decrease in the “blood-thinning” (anticoagulant) effect.

While you are taking warfarin, it is very important to tell your doctor or pharmacist of any changes in medications, vitamins, or herbal products that you are taking. The enzyme that carries out the carboxylation of glutamic acid is gamma-glutamyl carboxylase. The carboxylation reaction proceeds only if the carboxylase enzyme is able to convert a reduced form of vitamin K (vitamin K hydroquinone) to vitamin K epoxide at the same time. The vitamin K epoxide is, in turn, recycled back to vitamin K and vitamin K hydroquinone by another enzyme, the vitamin K epoxide reductase (VKOR). Warfarin inhibits VKOR[86] (specifically the VKORC1 subunit[87][88]), thereby diminishing available vitamin K and vitamin K hydroquinone in the tissues, which decreases the carboxylation activity of the glutamyl carboxylase.

Warfarin side effects

R-warfarin is metabolized to 4′-hydroxywarfarin by CYP2C8 with some contirbuting by CYP2C19, 6- and 8-hydroxywarfarin by CYP1A2 and CYP2C19, 7-hydroxywarfarin by CYP1A2 and CYP2C8, and lastly to 10-hydroxywarfarin by CYP3A4. The 10-hydroxywarfarin metabolite as well as a benzylic alcohol metabolite undergo an elimination step to form dehydrowarfarin. The minor pathway of metabolism is the reduction of the ketone group to warfarin alcohols, comprising 20% of the metabolites. Limited conjugation occurs with sulfate and gluronic acid groups but these metabolites have only been confirmed for R-hydroxywarfarins.

Do not take warfarin if you cannot take it on time every day. All patients must be appropriately selected and trained. Currently available self-testing/self-management devices give INR results that are comparable with those obtained in laboratory testing. This medication may be prescribed for other uses; ask your doctor or pharmacist for more information. Keep all appointments with your doctor and the laboratory.

Warfarin increases your risk of severe or fatal bleeding, especially if you have certain medical conditions, if you are 65 or older, or if you have had a stroke, or bleeding in your stomach or intestines. Seek emergency help if you have any bleeding that will not stop. Dicoumarol was a product of the plant molecule coumarin (not to be confused with Coumadin, a later tradename for warfarin).

Please read our disclaimer for more information about our website. Drugwatch’s trusted legal partners support the organization’s mission to keep people safe from dangerous drugs and medical devices. The dosage and administration of warfarin is individualized for each patient according to their blood tests and conditions. The information on Drugwatch.com has been medically and legally reviewed by more than 30 expert contributors, including doctors, pharmacists, lawyers, patient advocates and other health care professionals. 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.

Herbal and Dietary Supplements

Some foods and beverages can interact with warfarin and affect your treatment and dosage. While taking this drug, eat a normal, balanced diet, and talk to your healthcare provider before you make any diet changes. Also, certain vegetable oils also contain large amounts of vitamin K. Too much vitamin K can decrease the effect of warfarin. This medicine, commonly used to treat or prevent blood clots, can increase the risk of heavy bleeding.

Clinical Trials

Warfarin should be used during pregnancy only if the potential benefit justifies the potential risk. Examples of drugs that can cause interactions with warfarin are listed below. 1) Prophylaxis and treatment of venous thromboembolism and related pulmonary embolism. Lab and/or medical tests (such as INR, complete blood count) must be done while you are taking this medication. This medication may interfere with certain lab tests (such as theophylline levels), possibly causing false test results.

Talk to your doctor about using a different medication (such as acetaminophen) to treat pain/fever. Low-dose aspirin and related drugs (such as clopidogrel, ticlopidine) should be continued if prescribed by your doctor for specific medical reasons such as heart attack or stroke prevention. Warfarin is used to prevent blood clots from forming or growing larger in your blood and blood vessels. It is prescribed for people with certain types of irregular heartbeat, people with prosthetic (replacement or mechanical) heart valves, and people who have suffered a heart attack. Warfarin is also used to treat or prevent venous thrombosis (swelling and blood clot in a vein) and pulmonary embolism (a blood clot in the lung). Warfarin is in a class of medications called anticoagulants (‘blood thinners’).

Vitamin K intake can affect the INR/PT measurement as well as the effectiveness of the drug. The American Heart Association states that patients should keep vitamin K intake “as consistent as possible.” Sudden increases of vitamin K foods may decrease the INR and warfarin’s effect, which could cause blood clots. While lowering vitamin K intake can increase INR and the effect of the medication. The FDA has stated that generic warfarin products are interchangeable. However, consult your doctor or pharmacist before switching warfarin products. Be careful not to take more than one medication that contains warfarin unless specifically directed by the doctor or health care provider who is monitoring your warfarin treatment.