Metronidazole

What is Metronidazole?

Metronidazole is an antibiotic that’s used to treat bacterial infections. It’s prescribed for various conditions including rosacea, infected gums and bacterial vaginosis.

Bacterial vaginosis is a common infection that results in unusual vaginal discharge. It’s not a sexually transmitted infection (STI), but it can increase your risk of getting chlamydia.

Symptoms include a burning sensation when you pee, a grey or green discharge from the vagina and an unpleasant ‘fishy’ smell.

Bacterial vaginosis happens when the natural balance of bacteria in your vagina changes. This sometimes occurs when you have sex with a new partner, have an IUD fitted or use perfumed products around your vagina. The PH balance within the vagina is delicate and introducing anything that upsets the balance can cause infection to thrive.

Metronidazole helps to restore the balance of bacteria in your vagina. Metronidazole is the active ingredient in the generic tablets and in the branded version Flagyl. The branded and generic version are made by different companies and come in slightly different packaging.

Metronidazole tends to be cheaper than Flagyl.

How does Metronidazole work?

Bacterial infections exist in the body by entering a suitable environment and then reproducing. The cells do this by multiplying. The active ingredients in metronidazole pass into the bacteria cells and stop them from producing the proteins they need in order to grow and multiply. Without the ability to multiply the infection weakens and the body uses its natural immune defences to clear up the remaining infection.

The vagina needs some ‘good bacteria’ to keep it healthy, but bacterial vaginosis is caused by the excessive growth of unwanted bacteria, and so the right balance needs to be restored.

What doses of Metronidazole are there?

There are three dosage sizes available: 200mg, 400mg and 500mg. The common prescription for bacterial vaginosis is one 400mg tablet taken twice a day.

How to take Metronidazole

Always take your medication as directed by your clinician. If you have any doubt, consult the patient leaflet that comes with your medicine.

When you take metronidazole for bacterial vaginosis our clinician will usually advise you to:

• take one 400mg tablet twice a day for seven days
• space the doses out evenly (most people take one tablet with breakfast and one with dinner).
• take the tablets with water.
• swallow the tablets whole.

How long does it take Metronidazole to work?

Metronidazole is a highly effective treatment for bacterial vaginosis. Most women will see their symptoms clear within two to three days, but it’s important to take the full week’s course even if you feel better. If you still have symptoms after your course of antibiotics has finished, let our clinician know.

What should I do if I make a mistake when taking Metronidazole?

If you forget to take your tablet, then you should take it as soon as you remember. If it’s almost time for you to take the next dose, miss the forgotten tablet and carry on as normal. Never take a double dose of metronidazole.

If you take too much metronidazole, seek medical attention immediately.

Medically reviewed by

Dr Daniel Atkinson

GP Clinical Lead

on August 02, 2022.

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