Pharmacogenomics · Pharmacology

Patients with 'Loss-of-Function' CYP2C9 alleles (*2 or *3) require which adjustment to their Warfarin therapy?

  1. A higher starting dose
  2. A lower starting dose
  3. No change in dose
  4. Twice daily dosing instead of once daily
Show answer and explanation

Correct answer: A lower starting dose

CYP2C9 is the primary enzyme that metabolizes the more potent S-enantiomer of warfarin. Reduced enzyme activity leads to higher drug levels and an increased risk of bleeding, necessitating a lower initial and maintenance dose.

Difficulty: Medium Question 17 of 20

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