A client is prescribed warfarin (an anticoagulant). Which laboratory value is monitored to assess its therapeutic effect?

WARFARIN (Coumadin) is monitored using PROTHROMBIN TIME (PT) and INR (international normalized ratio). NCLEX physiological/pharmacology. The therapeutic INR for most conditions is 2.0-3.0 (higher for some, e.g., mechanical heart valves). A too-high INR means increased bleeding risk; too-low means inadequate anticoagulation. The ANTIDOTE for warfarin is VITAMIN K. TEACHING: maintain consistent vitamin K intake (leafy greens) — don't suddenly change diet; watch for bleeding; many drug/food interactions. CONTRAST: HEPARIN is monitored with aPTT (activated partial thromboplastin time); its antidote is protamine sulfate. Knowing warfarin → PT/INR (vitamin K antidote) and heparin → aPTT (protamine antidote) is a heavily tested NCLEX pharmacology pairing.