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Molecule Description

Warfarin prevents the formation of clots in blood vessels and their migration along the blood flow to distant parts. It belongs to a class of medicines called anticoagulants.

Uses of Warfarin

  • Atrial fibrillation (rapid, irregular heartbeats)
  • Rheumatic heart disease (disease of heart valves)
  • Deep Vein Thrombosis (DVT) (blood clots in deeper veins, usually the legs)
  • Pulmonary embolism (a blood clot passes along blood flow and blocks arteries that supply the lungs, most commonly from deep veins of the leg)
  • Transient Ischemic Attack (TIA) (clots in the blood vessels supplying the brain causing temporary damage)

Contraindications of Warfarin

When should one not use Warfarin

  • Allergy/ allergic reactions to Warfarin or any other ingredients of the medicine
  • Uncontrolled bleeding
  • Open wounds
  • Active ulcer disease; infection of the outer lining of the heart (pericarditis)
  • Rupture of blood vessels in the brain (haemorrhagic stroke)
  • Recent brain, eye or spinal cord injury or surgery (within 72 hours)
  • Liver or kidney disease
  • Uncontrolled hypertension
  • Any condition that causes easy bruising (Cushing’ syndrome, haemophilia, end-stage kidney disease, etc.)

Side effects of Warfarin

Common side effects of this drug are:

  • Unexplained bleeding from the nose
  • Black or red stools due to internal bleeding
  • Dark red or brown urine which may be due to your kidney or bladder conditions
  • Fever
  • Nausea and vomiting
  • Allergic reactions
  • Skin rashes & hair loss
  • Diarrhea
  • Purple discolouration of the skin (bruising)
  • Jaundice (yellowing of skin or white of eyes)
  • Changes in the quantity of urine you pass
  • Painful skin rash that may lead to severe complications (serious but rare)

Precautions and Warnings of Warfarin


Can I take Warfarin during pregnancy?
Warfarin has the potential to cross the placental barrier and causes severe damage to the unborn baby and is not recommended during or if you are planning a pregnancy.

Breast Feeding

Can I take Warfarin while breastfeeding?
Warfarin does not pass into breast milk but caution is advised while breastfeeding. It is recommended that a woman who wishes to breastfeed while taking Warfarin should consult with a doctor.


Can I drive if I have consumed Warfarin?
Warfarin does not affect your driving ability.


Can I consume alcohol with Warfarin?
Large amounts of alcohol while may reduce Warfarin levels in the blood and hence occasional mild to moderate alcohol consumption is permitted.

Other General Warnings

Talk to your doctor if
  • You have blood disorders (such as anemia, hemophilia)
  • Bleeding problems (bleeding of the stomach/ intestines)
  • Bleeding in the brain
  • Blood vessel disorders (such as aneurysms)
  • Recent major injury/ surgery
  • Kidney and liver disease
  • Alcohol use
  • Mental/ mood disorders (including memory problems)
  • Frequent falls/ injuries, risk of haemorrhage (any clotting factor deficiency)
  • Ulcers in the stomach (or elsewhere)
  • Any planned surgeries or dental procedures
  • Thyroid disorders
  • To monitor prothrombin time (time taken for the blood to clot) in the initial days of starting the therapy

Mode of Action of Warfarin

How Does It Work?

Warfarin helps to keep blood flowing smoothly in your body by decreasing the amount of certain substances (clotting proteins) derived from Vitamin K in your blood. Effectively, Warfarin works by reducing the levels of clotting substances in the blood.
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Interactions of Warfarin

Interactions with other medicines

  • NSAIDs (painkillers) medications increases the risk of gastrointestinal bleeding
  • Other similar medicines that reduce clotting (Clopidogrel, Bivalirudin, Dabigatran, Dipyramidole, Fondaparinux, Rivaroxaban, Tirofiban, Abciximab, Prostacyclin, Aspirin, etc.)
  • Medicines that increase the effect of Warfarin (Allopurinol, Erlotinib, Disulfiram, Ketoconazole, Fluconazole Statins, Erythromycin, Metronidazole, Omeprazole, Amiodarone, pain killers, Zafirlukast)
  • Medicines that decrease the effect of Warfarin (Phenobarbital, Phenytoin, Carbamazepine, Griseofulvin, oral contraceptives, Rifampicin, Azathioprine, etc.)
  • Antidepressant medications (Fluoxetine, Paroxetine, Sertraline, Citalopram, Duloxetine, Venlafaxine, Desvenlafaxine, etc.)
  • Some HIV medicines (Protease inhibitors - Nelfinavir, Ritonavir)
  • Corticosteroids (Prednisolone, Betamethasone, Triamcinolone, etc.)
  • Fibrinolytic drugs (Streptokinase, Alteplase)
  • Other medicine used to prevent or treat clot formation

Interactions with food items

Warfarin can be taken without regard to food – before or after meals.

Dietary Restrictions of Warfarin

  • Foods rich in Vitamin K include beef liver, broccoli, sprouts, cabbage, soya beans, spinach may interact with Warfarin
  • Drinking cranberry juice or taking other cranberry products (for example capsules or concentrates), might increase Warfarin’s “thinning” effect of the blood
  • Limit intake of garlic, ginger, gingko (used for mental disorders) and horse chestnut (used for healthy veins)

Dosage of Warfarin


If you take an overdose of Warfarin, the complications may be fatal. Speak to your doctor immediately. Depending on your condition and overdosage, you may require hospital admission for treatment and monitoring.
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Missed a Dose

Take the missed dose as early as you remember. Skip the dose if it is almost time for your next scheduled dose. Do not take two doses in a day to compensate the missed dose as the complications can be life-threatening.
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Content Details


Dr. Ritu Budania

MBBS, MD (Pharmacology)

Frequently Asked Questions (FAQs)


Q: What is the best time to take Warfarin?

A: Warfarin can be taken at any time before or after meals but it is usually preferred in the evening. This is because the prothrombin test (to check the time taken for the blood to clot) is generally performed in the early morning and if a dose change is required, it can be done the same day after the blood test result.

Q: How to store this medicine?

A: Store in a cool dark place (not above 25-degree Celcius), in original package out of reach of children and pets. Check the expiry date at the time of buying.
Last Updated on: 05 Oct 2020 | 10:47 PM (IST)

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The information provided herein is accurate, updated and complete as per the best practices of the Company. Please note that this information should not be treated as a replacement for physical medical consultation or advice. We do not guarantee the accuracy and the completeness of the information so provided. The absence of any information and/or warning to any drug shall not be considered and assumed as an implied assurance of the Company. We do not take any responsibility for the consequences arising out of the aforementioned information and strongly recommend you for a physical consultation in case of any queries or doubts. Please click here for detailed T&C.
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