LARA YUNG DI NAGAGALAW

• Cytochrome inhibitors


  • 1A2: cimetidine
  • 2C9: amiodarone
  • 2D6: cimetidine, amiodarone, paroxetine, bupropion
  • 3A4: verapamil, diltiazem, clarithromycin, erythromycin and grape fruit juice
• Cytochrome inducers


  • 1A2: tobacco, phenytoin and phenobarbital
  • 2C9: rifampicin
  • 3A4: rifampicin, phenytoin and phenobarbital
• Cytochrome substrates


  • 2D6: codeine and dextromethorphan
  • 2B6: bupropion
  • 2C9: ibuprofen, celecoxib (NSAIDs), losartan, irbesartan, warfarin and phenytoin
  • 2C19: Clopidogrel and phenytoin
  • 3A4: ethinylestradiol, rivaroxaban, apixaban, verapamil, diltiazem, erythromycin, aripiprazole, felodipine, nifedipine, amiodarone, fluvastatin, cyclosporin, colchicine
• Rivaroxaban+ ketoconazole


  Increases rivaroxaban level
• Clarithromycin+ verapamil


  Increases level or effect of verapamil
• Verapamil and erythromycin should not be taken together because both affect 3A4
• Erythromycin


  Interacts with oral anti-coagulant, carbamazepine (decreases metabolism leading to increased toxicity), digoxin and theophylline (increases their serum level)
• Erythromycin+ zafirlukast


  Decreases zafirlukast effect
• Lidocaine


  Metabolized 90% by 1A2 and 10% by 3A4. Cytochrome of it is 1A2.
• Ciclosporin+ erythromycin, diltiazem, verapamil and Allopurinol

  Increases cyclosporin
• Azathioprine+ allopurinol


  May be used by decreasing dose of azathioprine, or increases level of both drugs
• Digoxin


  Is a P-glycoprotein
• Digoxin+ amiodarone


  Decreases dose of digoxin to half
• Drugs that increase digoxin toxicity

  • Furosemide, chlorthalidone, spironolactone and cimetidine
• Quinine and quinidine


  Are contraindicated with digoxin as they increase digoxin level by decreasing its clearance
• Digoxin absorption


  Decreased by kaolin, neomycin and cholestyramine
• Simvastatin+ cholestyramine


  Decreases statin absorption
• Gemfibrozil+ atorvastatin


  Increases atorvastatin toxicity and increases myopathy risk
• Colchicine+ statin


  Causes myopathy
• Colchicine+ grape fruit


  Increases its toxicity
• Nifedipine, warfarin, digoxin and phenytoin+ grapefruit have no interaction
• Paracetamol+ methotrexate have no interaction
• Famotidine or Gingko biloba + warfarin have no interaction
• Digoxin+ lithium, theophylline have no interaction
• Doxorubicin and glucosamine have no interaction
• Measure 2C9: NSAIDs specially ibuprofen
• Measure 3A4: erythromycin (has most of it)
• Measure 2D6: dextromethorphan (first choice in cough suppression)
• Fluconazole+ omeprazole


  Increases omeprazole level
• Cytochrome P450 4A3 is not important in human metabolism
• Ciprofloxacin is not a substrate of cytochrome P450 2D6
• Esomeprazole is taken every morning

  Increases the dose of levothyroxine that needs to be increased
• Stop alcohol 24 hrs. before starting metronidazole
• Drugs that can cause disulfiram-like reaction

  • Ethanol
  • β-lactams (cephalosporins)
  • Chloramphenicol
  • Isoniazid
  • Ketoconazole
  • Griseofulvin
  • Metronidazole
  • Chlorpropamide
  • Sulphonylurea
  • Sulfonamide (methprim)
  • Chloral hydrate
• Drugs that require dose adjustment in renal failure

  • Ceftazidime
  • Allopurinol
  • Acyclovir
  • Ciprofloxacin
  • Digoxin
  • Methyl dopa
  • Amikacin
  • Enoxaparin
  • Metformin
  • Morphine
  • Lithium
  • Vancomycin
  • Baclofen
• Phenytoin, theophylline and diltiazem do not require dose adjustment in renal failure
• Fosinopril is the only ACEIs that can be used in renal failure as it is excreted in bile
• Drugs that require dose adjustment in hepatic failure

  • Theophylline
  • Amiodarone
  • Heparin
  • Metronidazole
  • Cefoperazone
  • Ceftriaxone
  • Chloramphenicol
  • Morphine
  • Nafcillin
• Drugs that do not have active metabolite

  • Phenytoin
  • Temazepam
  • Gentamicin
  • Nifedipine
  • Paracetamol
  • Acyclovir
• Drugs that require therapeutic drug monitoring

  • Digoxin
  • Amiodarone
  • Ciclosporin
  • Gentamicin
  • Phenytoin
  • Aminophylline
  • Lithium
  • Vancomycin