Pharm 101: Metronidazole


Nitroimidazole antiprotozoal drug

  • Selectively absorbed by anaerobic bacteria and sensitive protozoa
  • Causes disruption of electron transport chain
  • PO/IV/suppository administration
  • Well absorbed
  • 99% bioavailability
  • Low protein binding 10-20%
  • Well distributed in tissues, including CSF
  • Hepatic metabolism
  • Renal excretion
    • Half-life 7.5 hours
Antimicrobial activity
  • Potent activity against anaerobes, including Bacteroides and Clostridium species
  • Clinical uses:
    • Anaerobic or mixed intra-abdominal infections
    • Vaginitis
    • Clostriudium difficile
    • Brain abscess
Adverse effects
  • Gastrointestinal
    • Nausea
    • Diarrhoea
    • Stomatitis
  • Neurological:
    • Headache
    • Metallic taste in mouth
    • Peripheral neuropathy with prolonged use
  • Thrombophlebitis
  • Disulfiram-like effect, therefore avoid alcohol
    • Inhibits aldehyde dehydrogenase and causes accumulation of acetaldehyde in blood
  • Inhibitions CYP 3A4 (responsible for metabolism of 50% of drugs)
    • Potentiates effect of warfarin
  • Hepatic insufficiency or renal failure require dose adjustment
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MBBS CCPU (RCE, Biliary, DVT, E-FAST, AAA) Rob is an Emergency Medicine Advanced Trainee based in Melbourne, Australia. He has special interests in medical education, ECG interpretation, and the use of diagnostic and procedural ultrasound in the undifferentiated and unwell patient.

Follow him on twitter: @rob_buttner | ECG Library |

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