Consumer medicine information

Flagyl® S

Flagyl® S (flaj-ill)

Active ingredients: Metronidazole benzoate (met-ro(h)-nide-ah-zole benz-o(h)-ate) 200 mg/5 mL oral suspension

Consumer Medicine Information (CMI)

This leaflet provides important information about using Flagyl S. You should also speak to your doctor or pharmacist if you would like further information or if you have any concerns or questions about using Flagyl S.

Where to find information in this leaflet:

1. Why am I using Flagyl S?
2. What should I know before I use Flagyl S?
3. What if I am taking other medicines?
4. How do I use Flagyl S?
5. What should I know while using Flagyl S?
6. Are there any side effects?
7. Product details

1. Why am I using Flagyl S?

Flagyl S contains the active ingredient metronidazole benzoate (liquid). Flagyl S is an antibiotic that belongs to a group of medicines called nitroimidazoles.

Flagyl S is used to treat certain infections caused by bacteria and other organisms in different parts of the body.

It is also used to prevent or treat certain infections that may occur during surgery.

This medicine works by killing or stopping the growth of bacteria and other organisms causing these infections.

Your doctor may have prescribed Flagyl S for another reason.

Ask your doctor if you have any questions about why Flagyl S has been prescribed for you.

This medicine is available only with a doctor’s prescription.

There is no evidence that this medicine is addictive.

2. What should I know before I use Flagyl S?


Do not use Flagyl S if:

  • you are allergic to metronidazole or any other nitroimidazoles, or any of the ingredients listed at the end of this leaflet.
  • Always check the ingredients to make sure you can use this medicine.
  • you have evidence of, or have a history of, a blood disorder.
  • you have, or have ever had, a disease of the brain, spinal cord or nerves.
  • the expiry date on the pack has passed. If you use this medicine after the expiry date has passed it may have no effect at all, or worse, an entirely different effect.
  • the packaging is torn or shows signs of tampering.

Check with your doctor if you:

  • have any allergies to any other medicines or any other substances such as foods, preservatives or dyes.
  • have or have ever had any health problems/ medical conditions including:
    – a blood disorder
    – disease of the brain, spinal cord or nerves
    – liver or kidney disease
    – an inflammatory disease of the small intestine (e.g., Crohn’s disease)
    – Cockayne syndrome
  • drink alcohol. Do not drink alcohol during (and for 24 hours after stopping) treatment with Flagyl S.

If you have not told your doctor or pharmacist about any of the above, tell them before you start using Flagyl S.

During treatment, you may be at risk of developing certain side effects. It is important you understand these risks and how to monitor for them. See additional information under Section 6. Are there any side effects?

Pregnancy and breastfeeding

Check with your doctor if you are pregnant or intend to become pregnant.

Talk to your doctor if you are breastfeeding or intend to breastfeed.

3. What if I am taking other medicines?

Tell your doctor or pharmacist if you are taking any other medicines, including any medicines, vitamins or supplements that you buy without a prescription from your pharmacy, supermarket or health food shop.

Some medicines may interfere with Flagyl S and affect how well it works. These include:

  • any medication that may cause ECG disturbances (certain anti-arrhythmics (medicines for heart rhythm disorders), certain antibiotics, psychotropic medicines)
  • warfarin or other medicines used to prevent blood clots
  • Antabuse® (disulfiram), a medicine used to treat chronic alcohol dependence
  • Medications containing alcohol (ethanol), e.g., some cough syrups
  • some anticancer drugs, such as carmustine, cyclophosphamide monohydrate, 5-fluorouracil or busulfan
  • phenytoin, a drug used to treat convulsions
  • phenobarbital (phenobarbitone), a medicine for convulsions or sedation
  • cimetidine, a medicine used to treat gastric reflux and ulcers
  • lithium, a medicine used to treat manic depressive illness and some other types of depression
  • cyclosporin, a medicine used to prevent organ transplant rejection or to treat immune responses

Check with your doctor or pharmacist if you are not sure about what medicines, vitamins or supplements you are taking and if these affect Flagyl S.

You may need different amounts of your medicine or you may need to take different medicines. Your doctor will advise you.

Your doctor and pharmacist may have more information on medicines to be careful with or avoid while taking Flagyl S.

4. How do I use Flagyl S?

Follow all directions given to you by your doctor and pharmacist carefully. They may differ from the information contained in this CMI.

If you do not understand the instructions on the box, ask your doctor or pharmacist for help.

How much to use

  • The dose will vary from patient to patient. Your doctor will decide the right dose for you.
  • Follow the instructions provided when Flagyl S was prescribed, including the number of days it should be taken.

How long to use

  • For treating infection, Flagyl S suspension is usually taken for 7 days, however, your doctor may decide to reduce or extend your treatment. Your doctor will tell you how much Flagyl S to take.

How to take Flagyl S suspension

Flagyl S suspension should be taken at least one hour before a meal or food.

This medicine works better if taken on an empty stomach.

If you forget to use Flagyl S

If it is almost time for your next dose, skip the dose you missed and take your next dose when you are meant to. Otherwise, take it as soon as you remember, then go back to taking it as you would normally.

Do not take a double dose to make up for the dose you missed.

If you have trouble remembering to take/use Flagyl S, ask your pharmacist for some hints.

If you use too much Flagyl S

If you think that you have used too much Flagyl S, you may need urgent medical attention.

You should immediately:

  • phone the Poisons Information Centre
    (by calling Australia 13 11 26)
  • contact your doctor, or
  • go to the Emergency Department at your nearest hospital.

You should do this even if there are no signs of discomfort or poisoning.

If you take too much suspension you may experience vomiting and a feeling of disorientation.

5. What should I know while using Flagyl S?

Things you should do

Call your doctor straight away if:

  • the symptoms of your infection do not improve or become worse
  • you become pregnant
  • you are about to start taking any new medicines

Some people being treated with metronidazole can experience mental health problems such as irrational thoughts, hallucinations, feeling confused or feeling depressed, including thoughts of self-harm or suicide.

These symptoms can occur even in people who have never had similar problems before. If you or others around you notice any of these side effects stop taking this medicine and seek medical advice straight away.

If you get a sore, white mouth or tongue while taking or soon after stopping Flagyl S treatment, tell your doctor. Also tell your doctor if you get vaginal itching or discharge.

This may mean you have a fungal/yeast infection called thrush. Sometimes the use of Flagyl S allows fungi/yeast to grow and the above symptoms to occur. Flagyl S does not work against fungi/yeast.

If you are using Flagyl S for 10 days or longer, make sure you have any tests of your blood and nervous system that your doctor may request.

If you need to have a blood test while using Flagyl S, tell your doctor as Flagyl S may affect the results of some laboratory tests.

Remind any doctor, dentist or pharmacist you visit that you are using Flagyl S.

Things you should not do

  • Do not give Flagyl S to anyone else, even if they have the same condition as you.
  • Do not use Flagyl S to treat any other medical complaints unless your doctor tells you to.
  • Do not stop taking your suspension if you feel better.
  • If you do not complete the full course prescribed by your doctor, all of the bacteria/organisms causing your infection may not be killed. These bacteria/organisms may continue to grow and multiply so that your infection may not clear completely or may return.

Driving or using machines

Be careful before you drive or use any machines or tools until you know how Flagyl S affects you.

While using Flagyl S you may feel dizzy or experience vertigo (spinning sensation), confused, hallucinations (see or hear things that are not there), convulsions (have fits) or temporary eyesight problems (such as blurred or double vision). If this happens, do not drive or use any machinery or tools.

Drinking alcohol

Tell your doctor if you drink alcohol.

Alcohol may make you feel very sick, vomit, have stomach cramps, headaches and flushing.

Do not drink alcohol during (and for 24 hours after stopping) treatment with Flagyl S.

Looking after your medicine

  • Keep Flagyl S suspension in a cool dry place where the temperature stays below 25°C.

Follow the instructions in the carton on how to take care of your medicine properly.

Store in a cool dry place away from moisture, heat or sunlight; for example, do not store it:

  • in the bathroom or near a sink, or
  • in the car or on window sills

Keep it where young children cannot reach it.

Getting rid of any unwanted medicine

If you no longer need to use this medicine or it is out of date, take it to any pharmacy for safe disposal.

Do not use this medicine after the expiry date.

6. Are there any side effects?

All medicines can have side effects. If you do experience any side effects, most of them are minor and temporary. However, some side effects may need medical attention.

See the information below and, if you need to, ask your doctor or pharmacist if you have any further questions about side effects.

Less serious side effects

Less serious side effects What to do

  • joint pain


  • oral thrush – white, furry, sore or inflamed tongue and mouth
  • dry mouth


  • hearing problems

Urinary disorders

  • unusual urination patterns (e.g., difficulty in passing urine, large amounts of urine, incontinence, or pus in urine)

Respiratory related

  • stuffy nose, nasal congestion


  • nausea, which may be accompanied by headache, loss of appetite, and vomiting
  • diarrhoea, stomach discomfort, abdominal cramping or constipation, strange taste in mouth

Central nervous system-related

  • confusion, irritability, depression, or sleeplessness
  • convulsions, dizziness, weakness, feeling of incoordination or uncoordinated movements
  • vertigo (spinning sensation)


  • Changes in electrical activity of the heart seen on an Electrocardiogram (QT prolongation) has been observed particularly when metronidazole was administered with drugs with potential to prolong QT interval.


  • skin rashes, flushing, itching


  • eye problems, including blurred or double vision


  • yellowing of the skin or eyes, which may be jaundice


  • vaginal thrush – sore and itchy vagina and/or discharge
  • dryness of the vagina or vulva
Speak to your doctor if you have any of these less serious side effects and they worry you.

Serious side effects

Serious side effects What to do
  • Allergic reaction. Some symptoms of an allergic reaction include skin rash, itching, shortness of breath or swelling of the face, lips or tongue, which may cause difficulty in swallowing or breathing.
  • If you have been on prolonged Flagyl S therapy you may experience unusual numbness of the feet or hands.
Stop using Flagyl S, and tell your doctor immediately

Tell your doctor or pharmacist if you notice anything else that may be making you feel unwell.

Other side effects not listed here may occur in some people.

Reporting side effects

After you have received medical advice for any side effect you experience, you can report side effects as follows:

Australia: Therapeutic Goods Administration online at

By reporting side effects, you can help provide more information on the safety of this medicine.

Always make sure you speak to your doctor or pharmacist before you decide to stop taking any of your medicines.

7. Product details

This medicine is only available with a doctor’s prescription.

What Flagyl S contains

Active ingredient
(main ingredient)
Flagyl S – 200 mg metronidazole benzoate/5 mL of liquid
Other ingredients
(inactive ingredients)
Flagyl S suspension also contains monobasic sodium phosphate, aluminium magnesium silicate, sucrose, methyl and propyl hydroxybenzoate, ethanol, natural soluble lemon flavour 50 06-0404, orange oil terpeneless.

Do not take this medicine if you are allergic to any of these ingredients.

What Flagyl S looks like

There are three forms of Flagyl: Flagyl tablets, Flagyl S suspension and Flagyl suppositories. Flagyl tablets and suppositories are covered by a separate CMI.

Flagyl S suspension (Aust R 27501) is a creamy white to yellow liquid with an orange/lemon odour in a 100 mL bottle.

Who distributes Flagyl S

Flagyl S is supplied in Australia by:

sanofi-aventis australia pty ltd
12-24 Talavera Road
Macquarie Park NSW 2113
Freecall No: 1800 818 806

This leaflet was prepared in March 2022.

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