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Cytochrome P-450 2C9 Isoenzyme

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Cytochrome P-450 2C9 Isoenzyme, CYP2C9, CYP2C9 Inducer, CYP2C9 Inhibitor, CYP2C9 Substrate

  • Precautions
  • CYP2C9 Deficiency related to Warfarin toxicity
  1. Higher risk for Warfarin toxicity and bleeding complications
  2. Start with lower doses
  3. Reaching a steady-state INR on Warfarin requires >3 months
  4. Voora (2005) Thromb Haemost 93:700-5 [PubMed]
  • Interactions
  • Metabolized by CYP2C9 (Substrates)
  1. Cardiopulmonary Drugs
    1. Carvedilol (Coreg)
    2. Tolbutamide
    3. Angiotensin Receptor Blockers (ARBs) affected
      1. Losartan (Cozaar)
      2. Irbesartan (Avapro)
    4. ARBs not affected by Cytochrome P450 System
      1. Valsartan
      2. Eprosartan
      3. Candesartan
  2. Miscellaneous
    1. Diclofenac
    2. Ibuprofen
    3. Piroxicam
    4. Celecoxib (Celebrex)
    5. Warfarin
    6. Glipizide
  • Interactions
  • Inhibitor of CYP2C9
  1. Neuropsychiatric drugs
    1. Fluoxetine (Prozac)
  2. Cardiopulmonary Drugs
    1. Amiodarone
    2. Zafirlukast (Accolate)
    3. Fluvastatin (Lescol)
  3. Antibiotics and Antifungals
    1. Fluconazole (Diflucan)
    2. Ketoconazole
    3. Metronidazole (Flagyl)
    4. Ritonavir
    5. Trimethoprim-sulfamethoxazole (Septra)
  • Interactions
  • Inducer of CYP2C9
  1. Neuropsychiatric drugs
    1. Carbamazepine
    2. Phenobarbital
    3. Phenytoin
  2. Antibiotics
    1. Rifampin