Marevan (Warfarin Sodium)

• Warfarin, a vitamin K antagonist, is indicated for several thromboembolic conditions.
• Prevention and treatment of thromboembolic disorders: reduces risk of deep‑vein thrombosis, pulmonary embolism, and systemic embolism in patients with elevated clotting risk.
• Prophylaxis of stroke in non‑valvular atrial fibrillation: lowers incidence of ischemic stroke by maintaining therapeutic anticoagulation in patients with irregular heart rhythm.
• Prevention of venous thromboembolism after orthopedic surgery: helps prevent deep‑vein thrombosis and subsequent pulmonary embolism in patients undergoing joint replacement or fracture repair.

• Warfarin inhibits the enzyme vitamin K epoxide reductase (VKOR), which is essential for recycling vitamin K to its active hydroquinone form. By blocking this step, the synthesis of vitamin K‑dependent clotting factors II, VII, IX and X in the liver is reduced, leading to decreased thrombin generation and prolonged clotting time, thereby providing anticoagulant effect. The effect is dose‑dependent and monitored using the international normalized ratio (INR) to maintain therapeutic anticoagulation.

Warfarin may cause a spectrum of adverse reactions ranging from mild to life‑threatening.

Common Side Effects

• Bleeding gums: minor oral bleeding that may occur spontaneously.
• Bruising: easy bruising of the skin after minor trauma.
• Nausea: occasional stomach upset or loss of appetite.
• Hair loss: mild alopecia observed in some patients.
• Fatigue: feeling of tiredness or low energy.
• Dizziness: light‑headed sensation, especially upon standing.

Serious or Rare Side Effects

• Severe hemorrhage: life‑threatening internal bleeding such as gastrointestinal or intracranial bleed.
• Skin necrosis: painful skin lesions, typically occurring early in therapy.
• Allergic reaction: rash, itching, swelling, or anaphylaxis in rare cases.
• Elevated liver enzymes: signs of hepatic injury requiring monitoring.

• When using warfarin, careful monitoring and patient-specific adjustments are essential to maintain safety.
• Dose adjustment: individualize dosage based on INR results and clinical response.
• Drug interactions: review all concomitant medications for potential potentiation of anticoagulant effect.
• Renal or hepatic impairment: use with caution and increase monitoring frequency.
• Pregnancy: contraindicated due to teratogenic risk (Category X); avoid use in pregnant women.
• Surgery or invasive procedures: discontinue or adjust therapy prior to operation to reduce bleeding risk.
• Store at ambient temperature: keep below 25°C, retain original packaging, protect from moisture.

Warfarin interacts with several medicines that can alter its anticoagulant effect.

Major Interactions (Avoid)

• Aminoglycoside antibiotics (e.g., gentamicin): potentiate anticoagulation, increasing bleeding risk.
• Antifungal agents (e.g., fluconazole): raise warfarin plasma concentrations, enhancing effect.
• Non‑steroidal anti‑inflammatory drugs (NSAIDs): additive effect on bleeding, may cause gastrointestinal hemorrhage.

Moderate Interactions (Monitor Closely)

• Acetaminophen: can modestly increase INR; monitor coagulation parameters regularly.
• Selective serotonin reuptake inhibitors (SSRIs): may increase bleeding tendency; check INR more frequently.
• Vitamin K‑rich foods or supplements: can reduce warfarin effectiveness; advise consistent dietary intake.