Dr. Rishal Rahman P: WARFARIN – Balancing Clot Prevention With Safe Monitoring
Dr. Rishal Rahman P, Clinical Pharmacist Intern at Aster MIMS Kottakkal, posted on LinkedIn:
”Day 14: WARFARIN – Balancing Clot Prevention with Safe Monitoring
Indications
Prevention and treatment of venous thromboembolism (VTE, DVT, PE)
Prevention of stroke/systemic embolism in atrial fibrillation
Prosthetic heart valve thromboprophylaxis
Secondary prevention after myocardial infarction
Mechanism of Action
Inhibits Vitamin K epoxide reductase complex (VKORC1) → prevents activation of clotting factors II, VII, IX, X and proteins C & S → ↓ coagulation.
Dosage
Initial: 2–5 mg/day orally
Maintenance: 2–10 mg/day (adjust per INR)
Target INR:
2.0–3.0 for most indications
2.5–3.5 for mechanical prosthetic valves
Clinical Pharmacist Tips
Monitor INR regularly (every 2–4 weeks once stable).
Maintain consistent dietary vitamin K intake (avoid sudden ↑/↓ in green leafy vegetables).
Strong drug–drug & food interactions → always check before prescribing.
Educate patients about bleeding signs (bruising, gum bleed, black stools).
Contraindications
Pregnancy (teratogenic)
Active bleeding, recent major surgery, hemorrhagic stroke
Severe uncontrolled hypertension
Poor compliance for monitoring
Drug Interactions
Increased effect (↑ bleeding risk): Antibiotics (e.g., metronidazole, TMP-SMX), amiodarone, antifungals, SSRIs
Decreased effect (↓ anticoagulation): Rifampin, carbamazepine, barbiturates, vitamin K-rich foods
NSAIDs, aspirin → ↑ bleeding risk (even without INR changes)
Adverse Drug Reactions (ADR)
Bleeding (most common, dose-dependent)
Skin necrosis (rare, usually within 3–10 days, esp. in protein C/S deficiency)
Purple toe syndrome
Teratogenicity (nasal hypoplasia, stippled epiphyses)”
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