Metronidazole

How it works

After reduction in anaerobic and protozoal organisms it generates reactive intermediates that damage microbial DNA, producing a bactericidal and antiprotozoal effect.

Prescribing in practice

• Warn patients to avoid alcohol during treatment and for a short period afterwards because of a disulfiram-like reaction; it also potentiates warfarin.
• A metallic taste, nausea and gastrointestinal upset are common, and prolonged or high-dose courses carry a risk of peripheral neuropathy.
• It is generally regarded as acceptable in pregnancy when indicated, though high single-dose regimens are usually avoided in favour of standard courses.

Monitoring

Routine laboratory monitoring is not required for short courses; review for neuropathy with prolonged use and INR if co-prescribed with warfarin.

Counselling the patient

• Do not drink any alcohol while taking it and for at least a couple of days after finishing.
• Complete the full course even if you feel better.
• Report numbness or tingling in the hands or feet.

Evidence & guidelines

Metronidazole is a standard component of UK and BASHH treatment regimens for anaerobic and protozoal genital tract infections.