Generic Name :  Warfarin.

Trade Name    : Marevan.

Drug Class     : Anticoagulants.

Forms Of The Drug:

  1. Powder for injection:  5mg/vial.
  2. Tablet: 1mg, 2mg, 2.5mg, 3mg, 4mg, 5mg, 6mg, 7.5mg, 10mg.

Mechanism of action

Warfarin is an oral anticoagulant that works by interfering with the body’s blood clotting process. Its mechanism of action involves inhibiting the synthesis of certain clotting factors in the liver, ultimately preventing excessive blood clot formation. Here’s how warfarin works:

  1. Inhibition of Vitamin K: Warfarin primarily acts by interfering with the function of vitamin K, a crucial component in the synthesis of blood clotting factors in the liver. Vitamin K is necessary for the production of clotting factors II, VII, IX, and X, as well as proteins C and S.
  2. Vitamin K Cycle: Vitamin K is involved in the post-translational modification of clotting factors in a process known as gamma-carboxylation. This modification is essential for the activation of clotting factors and their subsequent participation in the coagulation cascade.
  3. Targeting Vitamin K Epoxide Reductase: Warfarin inhibits an enzyme called vitamin K epoxide reductase, which plays a key role in the recycling of vitamin K to its active form. By inhibiting this enzyme, warfarin reduces the availability of active vitamin K, thereby decreasing the gamma-carboxylation of clotting factors.
  4. Delayed Effect: Warfarin’s effects take time to manifest due to the gradual depletion of active clotting factors. It typically takes several days for the full anticoagulant effect to occur after starting or adjusting the dosage of warfarin.
  5. Anticoagulant Effect: By reducing the activity of clotting factors II, VII, IX, and X, warfarin decreases the ability of the blood to clot effectively. This anticoagulant effect helps prevent the formation of new blood clots and reduces the risk of clot-related conditions such as deep vein thrombosis (DVT), pulmonary embolism (PE), and stroke in certain clinical settings.
  6. Individualized Dosing: Warfarin has a narrow therapeutic window, and its dosage needs to be carefully monitored and adjusted based on regular blood tests measuring the International Normalized Ratio (INR). The INR helps assess the clotting tendency of blood and ensures that the dose is within the desired range for preventing blood clots without causing excessive bleeding.

Indications

  1. Atrial Fibrillation.
  2. Venous Thromboembolism (VTE).
  3. Prosthetic Heart Valves.
  4. Post-Cardiac Surgery: (like valve replacement or repair).
  5. Hypercoagulable States.
  6. Stroke Prevention in Certain Cases.

Contraindications

  1. Active Bleeding or High Bleeding Risk.
  2. Hypersensitivity to Warfarin.
  3. Severe Hypertension.
  4. Recent Surgery or Trauma.
  5. Pregnancy (in certain situations).
  6. Severe Liver Disease.
  7. Severe Kidney Disease.
  8. Alcoholism or Conditions Predisposing to Bleeding.

Side Effects

  1. Bleeding.
  2. Hematoma Formation.
  3. Nausea and Vomiting.
  4. Skin Changes: Warfarin might cause skin changes, such as a purple toe syndrome.
  5. Hair Loss.
  6. Skin Rash or Itching.
  7. Bone Loss (Osteoporosis).
  8. Other less common side effects include changes in taste, abdominal pain, diarrhea, and fever.

Drug Interactions

Other drugs that can interact with it.

  1. Antibiotics and Antifungal Medications: Certain antibiotics (e.g., ciprofloxacin, erythromycin) and antifungal medications (e.g., fluconazole).
  2. Antiplatelet Medications: Combining warfarin with antiplatelet drugs like aspirin, clopidogrel, or nonsteroidal anti-inflammatory drugs (NSAIDs).
  3. Heparin and Low Molecular Weight Heparins (LMWH): Concurrent use of warfarin with heparin or LMWH (e.g., enoxaparin).
  4. Anticonvulsants: Some anticonvulsants (e.g., phenytoin, carbamazepine).
  5. Herbal Supplements and Natural Products: Herbal supplements like ginseng, garlic, gingko biloba, and vitamin E.
  6. Vitamin K Intake: Foods rich in vitamin K, like leafy green vegetables (e.g., spinach, kale).
  7. Other medications like statins (cholesterol-lowering drugs), selective serotonin reuptake inhibitors (SSRIs), and certain cardiovascular medications.

Precautions

  1. Pregnancy: Category X.
  2. Lactation: Warfarin is known to pass into breast milk, and while limited information is available regarding its effects on nursing infants, caution is advised when considering its use during breastfeeding.

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