Anticoagulants · Pharmacology

Which of the following laboratory tests is most commonly used to monitor the therapeutic effect of Warfarin?

  1. Activated partial thromboplastin time (aPTT)
  2. Prothrombin Time (PT) / INR
  3. Bleeding time
  4. Thrombin time
Show answer and explanation

Correct answer: Prothrombin Time (PT) / INR

Warfarin inhibits the synthesis of Vitamin K-dependent factors (II, VII, IX, X). Since Factor VII has the shortest half-life and is part of the extrinsic pathway, the PT/INR is the most sensitive and standardized test for monitoring.

Difficulty: Medium Question 2 of 20

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