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Antibacterial / antiprotozoal (nitroimidazole)

Metronidazole: uses, side effects & precautions

Also known as Flagyl, metronidazole, MetroGel-Vaginal, Rozex.

This information is for general guidance only and does not constitute medical advice. Always consult a qualified healthcare professional for personal medical concerns. In an emergency, call your local emergency number.

What it is used for

  • Bacterial vaginosis
  • Trichomoniasis (a sexually transmitted infection)
  • Certain other bacterial and protozoal infections (under medical advice)

How it works

It kills the bacteria and certain parasites responsible for these infections by damaging their genetic material, restoring the normal balance in the vagina or clearing the infection.

How it is taken

Comes as oral tablets and as a vaginal gel, and is also used for other infections in different forms. Complete the full course exactly as your doctor, pharmacist, or label directs, even if you feel better, and ask about avoiding alcohol during and just after treatment.

No doses here on purpose. The right strength and schedule depend on you — only a doctor or pharmacist should set them. Always follow your prescription and the label.

Common side effects

  • Nausea
  • Metallic taste
  • Loss of appetite
  • Furred tongue
  • Headache
  • Stomach upset
  • Dark urine (harmless)

Serious effects — get help

  • Severe or watery diarrhoea (possible gut infection)
  • Numbness or tingling in hands or feet
  • Seizures
  • Severe skin reaction
  • Signs of a serious allergic reaction

If a reaction is severe — for example trouble breathing, swelling of the face or throat, or collapse — go to the nearest emergency room now or call your local emergency number. Do not wait for an online consultation.

Interactions to watch

  • Alcohol (can cause flushing, nausea, and vomiting during and shortly after treatment)
  • Some blood-thinning medicines
  • Lithium and some other medicines
  • Tell your clinician about all your medicines

Who should take care

  • Avoid alcohol during treatment and for a short period after, as advised
  • Complete the whole course to fully clear the infection
  • For trichomoniasis, sexual partners usually need treatment too
  • Tell your clinician if you are pregnant or breastfeeding, or have liver or nervous system conditions

Frequently asked questions

Why can't I drink alcohol with it?
Combining alcohol with this medicine can cause unpleasant flushing, nausea, and vomiting, so avoid it during and shortly after the course.
Is bacterial vaginosis a sexually transmitted infection?
It is not classed as an STI, but it relates to the balance of vaginal bacteria. Your clinician can advise on prevention of recurrence.
Does my partner need treatment?
For trichomoniasis, partners usually need treating. For bacterial vaginosis, routine partner treatment is generally not needed; ask your clinician.
What if symptoms return?
Recurrent symptoms should be reviewed by a clinician, as repeated or different treatment may be needed.
Is Metronidazole safe to take?
For most people it is safe when taken exactly as a doctor or pharmacist advises and as printed on the label. Tell your clinician about your other medicines and health conditions, and seek urgent care for any serious reaction.

Related conditions

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