Metronidazole in diarrhoeal illness
Current indications, limitations, and important safety considerations
What is metronidazole?
Active against anaerobic bacteria and selected protozoa. Modern practice is more selective as better-targeted therapies exist.
When metronidazole IS appropriate
- Giardiasis
- Amoebiasis (often followed by a luminal agent)
- Selected anaerobic GI infections (specialist-directed)
When metronidazole should NOT be used
- Routine acute diarrhoea
- Viral gastroenteritis
- Uncomplicated traveller’s diarrhoea
- Empiric “just in case” treatment
C. diff update
Metronidazole is no longer first-line for C. diff. First-line: oral vancomycin or fidaxomicin. Metronidazole may be used only if first-line agents unavailable and disease mild under supervision.
Important safety considerations
Alcohol interaction
Avoid alcohol during treatment and for at least 48 hours after the last dose (risk of disulfiram-like reaction).
Neurological side effects
With prolonged/repeated courses: peripheral neuropathy, dizziness, ataxia. Neuropathy may be slow to resolve.
Drug interactions
Warfarin (increased effect), alcohol, and other hepatic metabolism interactions.
Key takeaway: Metronidazole has a specific, limited role. Use it for the right infection — and avoid otherwise.