Ornidazole

Key facts

• Ornidazole is a nitroimidazole antimicrobial that kills protozoa and bacteria that grow without oxygen.
• Most courses run for a few days to a week and are usually taken with food to limit stomach upset.
• Avoid alcohol during treatment and for at least a couple of days afterward; the combination can cause flushing, nausea and a fast heartbeat.
• Seek urgent care for numbness or tingling in the hands or feet, confusion, or a seizure.

What ornidazole treats

Ornidazole treats infections caused by anaerobic bacteria and protozoa. This includes bacterial vaginosis, trichomoniasis, a sexually transmitted parasite infection, amoebic dysentery and liver abscess caused by Entamoeba histolytica, and giardiasis, a parasite infection of the small intestine often linked to contaminated water. It is also used to prevent infection after some types of bowel surgery.

How ornidazole works

Inside susceptible bacteria and parasites, ornidazole is converted to a reactive form that breaks strands of the organism's DNA. This stops the microbe multiplying and lets your immune system clear the infection.

Before you take it

• Avoid ornidazole if you have a known allergy to nitroimidazole antimicrobials, such as metronidazole or tinidazole.
• Tell your prescriber about any nerve disorder, epilepsy, or significant liver disease, since prolonged or high-dose treatment has been linked to peripheral nerve damage and seizures.
• Tell your prescriber if you are pregnant or breastfeeding; use in early pregnancy is generally avoided.
• Do not drink alcohol during treatment.

Side effects

Common effects include nausea, a metallic taste, headache and mild dizziness.

Seek urgent medical care for:

• Numbness, tingling, or weakness in the hands or feet.
• Confusion, unsteady walking, or a seizure.
• Persistent vomiting or diarrhoea leading to dehydration.
• Yellowing of the skin or eyes, or dark urine.
• Swelling of the face, lips or throat, or difficulty breathing.

Safety essentials

• Stop treatment and contact a doctor promptly if you develop tingling, numbness, or weakness; nerve damage from nitroimidazole drugs usually reverses if caught early but can persist if treatment continues.
• Do not drink alcohol during treatment or for a couple of days after finishing it.
• Finish the full course even if you feel better, so the infection clears completely and does not return.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.