Metronidazole: uses, dosing and precautions

It is available in oral, intravenous, vaginal and skin preparations. These forms are not interchangeable: the prescribed route, dose and course reflect where the infection is and which organisms are suspected.

Metronidazole acts against particular bacteria that thrive with little oxygen and against certain parasites. It may be used for some dental, abdominal, pelvic or vaginal infections and for giardiasis. It does not treat viral illnesses such as a cold.

A metallic taste, nausea, reduced appetite, abdominal discomfort, diarrhoea or headache can occur. Darker urine may also appear during treatment. Side effects and interactions differ with the formulation and with other medicines, so the packet instructions apply to the product supplied.

Take doses at the directed times and complete the prescribed course unless a clinician tells you to change it. If tablets upset your stomach, follow the label's advice about taking them with food. Do not double a dose after forgetting one; use the packet directions or ask a pharmacist.

Avoid alcohol while using metronidazole and for the period stated in the medicine instructions after the final dose, because the combination can cause unpleasant symptoms. Tell the prescriber about pregnancy, breastfeeding, liver problems, neurological conditions and all medicines, particularly blood thinners, lithium or seizure treatments.

Seek emergency assistance for breathing difficulty, fainting, facial or throat swelling, a seizure, or a widespread blistering or peeling rash. Stop driving and obtain prompt advice if severe dizziness, confusion or poor coordination develops.

Contact a clinician promptly for new numbness, tingling or burning in the hands or feet, yellow skin or eyes, severe abdominal pain, persistent vomiting, or severe or bloody diarrhoea. Report an infection that is worsening or not responding as expected rather than extending the course yourself.

Ask what organism or infection is being targeted, how and when to use the formulation, and what to do about a missed dose. Confirm the alcohol restriction printed for your product and whether any current medicine needs monitoring or adjustment during the course.