Metronidazole

Mechanism of Action

• Covalently binds to anaerobic bacterial DNA (anaerobes are unable to reduce metronidazole to inactive form)- causes bacterial death (bacteriocidal)

Indications

• Anaerobic bacterial infections e.g. dental/gum infections; intra-abdominal/biliary tree infections; occasionally aspiration pneumonia; abscesses/fistulating disease; bad skin infections
• Protozoal infections e.g. Trichomonas vaginalis

Cautions

• Do not take with alcohol
• In severe liver disease, reduce the dose to one-third (avoid if possible)
• If used for long-period, it is recommended that blood monitoring (FBC, U&E and LFT)

Side effects

• Common
  • GI disturbance (inc nausea and vomiting); taste disturbance; furred tongue; oral mucositis; anorexia
• Very rare
  • Hepatitis; jaundice; pancreatitis;
  • drowsiness; dizziness; headache; ataxia; psychotic disorders;
  • Darkening of urine
  • Thrombocytopenia, pancytopenia
  • Myaligia, arthralgia
• Prolonged intensive therapy
  • Peripheral neuropathy
  • Leucopenia
  • Seizures
  • Rarely aseptic meningitis; optic neuropathy

Interactions

• Alcohol
• Warfarin – increases effect
• May increase plasma levels of antiepileptics e.g. phenytoin