Marevan Forte (Warfarin Sodium)

Warfarin is a vitamin K antagonist used to reduce the risk of clot formation in several cardiovascular conditions.

• Atrial fibrillation: reduces the risk of stroke and systemic embolism in patients with non‑valvular atrial fibrillation.
• Deep vein thrombosis: treats existing clots and prevents recurrence of DVT in the lower extremities.
• Pulmonary embolism: manages acute pulmonary emboli and lowers the chance of subsequent embolic events.
• Prosthetic heart valves: provides prophylaxis against thromboembolism in patients with mechanical heart valve prostheses.

• Warfarin inhibits the enzyme vitamin K epoxide reductase (VKOR), which is required to regenerate reduced vitamin K. By blocking this cycle, the drug decreases the γ‑carboxylation of vitamin K‑dependent clotting factors II, VII, IX and X, as well as proteins C and S, leading to reduced synthesis of functional clotting factors and prolonged coagulation time, thereby impairing the clotting cascade.

Warfarin may cause a range of adverse reactions, varying from mild to potentially life‑threatening.

Common Side Effects

• Minor bleeding such as gum bleeding, nosebleeds, or easy bruising.
• Gastrointestinal upset including nausea, abdominal pain, or dyspepsia.
• Skin reactions like mild rash, itching, or localized redness.
• Transient elevation of liver enzymes without clinical hepatitis.
• Headache or dizziness, often transient.

Serious or Rare Side Effects

• Severe hemorrhage, including intracranial bleeding or massive gastrointestinal bleed.
• Warfarin‑induced skin necrosis presenting as painful, purplish skin lesions.
• Purple toe syndrome characterized by painful discoloration and necrosis of the toes.

When prescribing warfarin, careful monitoring and patient education are essential to minimize risks.

• Dose adjustment: individualize dose based on INR monitoring and clinical response.
• Dietary considerations: maintain consistent intake of vitamin K‑rich foods to avoid fluctuations.
• Concomitant medications: review all drugs for potential interactions that may alter anticoagulant effect.
• Pregnancy and lactation: contraindicated in pregnancy (Category X) and not recommended while breastfeeding.
• Patient education: advise patients to report any signs of bleeding promptly.
• Store at ambient temperature: keep tablets in the original container, protect from moisture and heat.

Warfarin’s anticoagulant effect can be significantly altered by other substances, requiring careful management.

Major Interactions (Avoid)

• Strong CYP2C9 inhibitors (e.g., amiodarone, fluconazole): markedly increase warfarin levels, risk of bleeding.
• Antiplatelet agents (e.g., aspirin, clopidogrel): additive anticoagulant effect, heightened bleeding risk.
• Non‑steroidal anti‑inflammatory drugs (NSAIDs): potentiate gastrointestinal bleeding when combined with warfarin.

Moderate Interactions (Monitor Closely)

• CYP2C9 inducers (e.g., rifampin, carbamazepine): reduce warfarin efficacy, may lead to clot formation.
• Certain antibiotics (e.g., macrolides, trimethoprim‑sulfamethoxazole): can modestly increase INR, requiring closer monitoring.
• Herbal supplements such as ginkgo or garlic: may enhance anticoagulation, monitor INR.