Warfarin is an anticoagulant taken orally to treat and prevent the formation of blood clots. The medication is also FDA-approved for the prophylaxis and treatment of venous thrombosis.

People who take warfarin reduce the clotting ability of the blood and prevent the risk of serious conditions like heart attack and stroke.

Warfarin is a blood thinner that works by altering the body’s clotting mechanism. It inhibits the formation of clotting factors that depend on vitamin K. By stopping the synthesis of vitamin K-dependent clotting factors, your body can prevent the formation of harmful clots.

Warfarin Precautions and Warnings

Using warfarin may lead to the development of gangrene or skin necrosis. Therefore, inform your doctor if you notice signs and symptoms like pain, temperature change, and skin color change.

Inform your doctor if you are allergic to warfarin or any of its ingredients to avoid serious allergic reactions or other problems.

Patients suffering from end-stage kidney disease have an increased risk of experiencing calciphylaxis after taking warfarin. Seek immediate medical attention if you experience symptoms like blotchy or net-like spots in your skin.

Warfarin increases the chances of bleeding such as nose bleeding, blood in your stool or urine, and unusual bruising or bleeding. Avoid using sharp objects like razor blades and nail clippers to minimize the risk of experiencing bruises, injuries, or cuts.

Avoid the consumption of alcohol while using warfarin because it may increase the chances of stomach bleeding and may interfere with the effectiveness of the medication.

Warfarin Side Effects

Warfarin has several side effects that may occur after taking it. Understanding the side effects is important for patients and healthcare providers to ensure safe and informed usage of warfarin. The side effects can either be mild or severe, and not all patients using warfarin can experience them.

Common Side Effects

  • Headaches
  • Profuse sweating
  • Dizziness
  • Fever
  • Coughing up blood
  • Stomach pains
  • Loss of appetite
  • Vision changes

Severe Side Effects

  • Blood in your stool or urine
  • Allergic reactions
  • Unusual bruising
  • Feeling weak
  • Skin discoloration
  • Nosebleeds
  • Heavy menstruation
  • Difficulty breathing

Drug Interactions with Warfarin

Warfarin may interact with different medications, certain foods, and supplements which can interfere with its effectiveness. Below are some potential interactions of Warfarin that you need to be aware of to ensure safe and effective use of the medication.

Drug Interaction
LevothyroxineThe interaction between warfarin and levothyroxine may increase the risk of anticoagulation by altering hepatic metabolism leading to bleeding.
FluconazoleFluconazole can interfere with warfarin causing elevated warfarin levels and increasing the risk of bleeding.
AtorvastatinConcurrent use of atorvastatin and warfarin can lead to a higher risk of bleeding specifically in patients with renal impairment or hepatic dysfunction.
ParacetamolCombining paracetamol and warfarin enhances the anticoagulant effects of Warfarin, which may lead to an increased risk of bleeding either long-term or high-dose acetaminophen use.
CiprofloxacinUsing warfarin concurrently with ciprofloxacin inhibits the metabolism of warfarin. This can lead to increased levels of warfarin in your blood and potentially increasing anticoagulant effects.
FluoxetineThe combination of these two medications inhibits platelet aggregation and increases bleeding, especially in vulnerable populations like those having bleeding disorders or the elderly.

Strengths and Dosages of Warfarin

Warfarin dosages will depend on several factors such as the severity of your condition, age, condition treated, other medical conditions, and how you will respond to the initial dose.

Age Dosage  No. of Times a Day
 Initial DosageMaintenance Dosage 
Adult2mg – 5mg2mg – 10mgOnce per day

The mediation is usually taken once per day in the evening, ideally at the same time every day. Warfarin can either be taken with or without food.

During the initial treatment with warfarin, frequent dosage adjustments may be necessary until your doctor determines the right dosage for your needs. The initial dosage for children is usually determined by their body weight.

Warfarin Alternatives

The alternative medications of warfarin offer different mechanisms of action but it also aims to prevent blood clots from occurring and reduce the risk of vein thrombosis and strokes. Your choice of medication will depend on various factors like your medical history and risk factors for clotting and bleeding. The alternatives include:

Warfarin FAQs

How does warfarin work?

Warfarin is an anticoagulant that inhibits the formation of blood clots by blocking the action of vitamin K responsible for the synthesis of proteins that are needed for clotting. By reducing the level of clotting factors, warfarin helps slow down the clotting process making it effective in reducing blood clots.

What are the best foods to eat while taking warfarin?

It is advisable to eat healthy foods containing up to five portions of fruits and vegetables daily. You should also keep the intake of vitamin K consistent by avoiding drastic dietary changes.

What are the symptoms of too much warfarin?

Taking too much warfarin may cause symptoms such as severe headache, dizziness or weakness, heavy vaginal bleeding, nosebleeds, prolonged bleeding from cuts, and coughing up blood.

What vegetables can I eat while on warfarin?

Patients on warfarin should eat healthy vegetables including tomato, okra, cucumbers, cooked spinach, raw dandelion greens, celery, and zucchini.

Why take warfarin at 6pm?

Taking warfarin in the early evening is recommended to ensure the medication’s effects are at peak late in the evening, potentially reducing the risk of bleeding complications during the day when activities are more frequent.

What vitamin interacts with warfarin?

Vitamin K when combined with Warfarin can cause interaction. Eating foods rich in vitamin K while taking the medication may affect the effectiveness of warfarin.

How long to hold warfarin before surgery?

Stop using warfarin 5 days before surgery. Use unfractured heparin three days before the surgery adjusted based on renal function. Two days to surgery asses INR, if above 1.5, administer vitamin K at a dose of 1 to 2 mg.

What happens if you miss a dose of warfarin?

If you miss the warfarin dosage, take it as soon as you remember. If your next dose is approaching leave the missed dosage and continue with your regular dosing schedule. Do not take a double dose.

How long does warfarin stay in your system?

Warfarin stays in your system for three to four days after which its effects disappear.

Which test determines appropriate warfarin therapy?

The International Normalized Ratio (INR) blood tests help measure the clotting time of your blood to determine the effectiveness of warfarin therapy and assess the appropriate dosage.

How long does it take for warfarin to work?

After taking warfarin, it may take approximately two to four days to observe its effects on your body.

Fruits to avoid when taking warfarin

Avoid taking cranberry and grapefruit juice while on warfarin medication.

IMPORTANT NOTE: The information provided here is for educational purposes only and is not intended to serve as medical advice, diagnosis, or treatment recommendations. It should not be taken as an endorsement of any specific medication or treatment. Individual health conditions and responses to treatment can vary greatly; therefore, this information should not be seen as a guarantee of safety, suitability, or effectiveness for any particular individual. Always consult with a healthcare professional for personalized medical advice and before making any decisions regarding your health or treatment plans.

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