A 72-year-old man with non-valvular atrial fibrillation is started on apixaban. Unlike warfarin, apixaban has a predictable pharmacokinetic profile. Which characteristic is most responsible for its predictable anticoagulation without routine monitoring?
- A Apixaban directly and reversibly inhibits Factor Xa with fixed dosing pharmacokinetics and minimal drug-drug or food interactions compared with warfarin ✓
- B Apixaban is exclusively renally cleared with no hepatic metabolism, giving predictable renal dose adjustment
- C Apixaban undergoes no protein binding, giving 100% free drug fraction predictably
- D Apixaban is a prodrug converted to its active form by gut esterases at a consistent rate
Correct answer: A. Apixaban directly and reversibly inhibits Factor Xa with fixed dosing pharmacokinetics and minimal drug-drug or food interactions compared with warfarin
Explanation
Apixaban is a direct, reversible Factor Xa inhibitor with predictable pharmacokinetics: fixed dosing, modest protein binding (~87%), dual elimination (renal ~27%, hepatic/biliary ~73%), and few significant food or CYP450 drug interactions compared with warfarin. Warfarin has narrow therapeutic index, requires INR monitoring, and has numerous gene-drug and food-drug interactions affecting CYP2C9 and VKORC1. Dabigatran is renally cleared >80% and is a prodrug converted by esterases, not apixaban. Apixaban is not 100% unbound.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.