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NCLEX · Pharmacological Therapies

A client is prescribed warfarin (Coumadin). Which laboratory value monitors the therapeutic effect of this medication?

Correct answer

INR (International Normalized Ratio) — the standardized measure of prothrombin time used to monitor warfarin; therapeutic range is typically 2.0-3.0 for most indications (2.5-3.5 for mechanical heart valves)

  1. A aPTT
  2. B INR (International Normalized Ratio) — the standardized measure of prothrombin time used to monitor warfarin; therapeutic range is typically 2.0-3.0 for most indications (2.5-3.5 for mechanical heart valves)
  3. C Platelet count
  4. D Serum potassium

Why this is the answer

WARFARIN MONITORING: INR (International Normalized Ratio) is the standardized PT measurement for warfarin. THERAPEUTIC RANGES: Most indications (atrial fibrillation, DVT/PE treatment): 2.0-3.0; Mechanical heart valves: 2.5-3.5; INR ABOVE RANGE: Excessive anticoagulation, bleeding risk — hold warfarin, possible vitamin K (antidote); INR BELOW RANGE: Insufficient anticoagulation, clot risk; PATIENT EDUCATION: Maintain consistent vitamin K intake (don't suddenly increase/decrease leafy greens — vitamin K antagonizes warfarin); avoid alcohol; report signs of bleeding; many drug interactions; CONTRAST: aPTT monitors HEPARIN (not warfarin); platelet count monitors for thrombocytopenia. The classic NCLEX confusion is warfarin/INR vs heparin/aPTT — memorize: 'WARfarin = INR; heparin = PTT.'
Source: NCLEX-PN Physiological — Pharmacology, Warfarin INR

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