Patient leaflet - Metronidazole 400 mg tablets
1. What Metronidazole tablets are and what they are used for
Metronidazole 200 mg and 400 mg Tablets (called Metronidazole tablets in this leaflet) contain the active substance metronidazole. This belongs to a group of medicines called antibiotics.
It works by killing bacteria and parasites that cause infections in your body. It can be used to:
Ÿ Treat infections of the blood, brain, lung, bones, genital tract, pelvic
area, stomach and intestines
Ÿ Treat gum ulcers and other dental infections
Ÿ Treat infected leg ulcers and pressure sores
Ÿ Prevent infections after surgery
If you need any further information on your illness, speak to your doctor.
2. What you need to know before you take Metronidazole tablets
Do not take Metronidazole tablets if:
X You are allergic (hypersensitive) to metronidazole, nitroimidazoles (e.g. tinidazole) or any of the other ingredients of this medicine (listed in section 6).
Signs of an allergic reaction include: a rash, swallowing or breathing problems, swelling of your lips, face, throat or tongue.
Do not take Metronidazole tablets if any of the above apply to you. If you are not sure, talk to your doctor or pharmacist before taking Metronidazole tablets.
Warnings and precautions
Talk to your doctor or pharmacist before taking Metronidazole tablets if:
Ÿ You have or have ever had a liver problem
Ÿ You are having kidney dialysis (see section 3 'People having kidney
dialysis')
Ÿ You have a disease of the nervous system
If you are not sure if any of the above apply to you, talk to your doctor or pharmacist before taking your medicine. Do this even if they have applied in the past.
Tell your doctor immediately and stop taking Metronidazole tablets if you develop stomach pain, anorexia (loss of appetite), nausea (feeling sick), vomiting (being sick), fever, malaise, fatigue, vertigo (spinning sensation), jaundice, dark urine, putty or mastic-coloured stools or itching.
Cases of severe liver toxicity/acute liver failure, including cases with a fatal outcome, in patients with Cockayne syndrome have been reported with Metronidazole tablets.
If you are affected by Cockayne syndrome, your doctor should also monitor your liver function frequently while you are being treated with Metronidazole tablets and afterwards.
Serious skin reactions including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), acute generalised exanthematous pustulosis (AGEP) have been reported with the use of metronidazole: Ÿ SJS/TEN can appear initially as reddish target-like spots or circular
patches often with central blisters on the trunk. Also, ulcers of the mouth, throat, nose, genitals and eyes (red and swollen eyes) can occur. These serious skin rashes are often preceded by fever and/or flu-like symptoms. The rashes may progress to widespread peeling of the skin and life-threatening complications or be fatal.
Ÿ AGEP appears at the initiation of treatment as a red, scaly widespread
rash with bumps under the skin and blisters accompanied by fever. The most common location: mainly localised on the skin folds, trunk, and upper extremities.
The highest risk for occurrence of serious skin reactions is within one week, typically, within 48 hours after start of treatment. If you develop a serious rash or another of these skin symptoms, stop taking Metronidazole tablets and contact your doctor or seek medical attention immediately.
Other medicines and Metronidazole tablets
Tell your doctor or pharmacist if you are taking, have recently taken or might take any other medicines. This includes medicines obtained without a prescription, including herbal medicines. This is because Metronidazole tablets can affect the way some other medicines work. Also, some other medicines can affect the way Metronidazole tablets work.
In particular tell your doctor if you are taking any of the following medicines: Ÿ Medicines used to thin the blood such as warfarin
Ÿ Lithium for mental illness
Ÿ Phenobarbital or phenytoin for epilepsy
Ÿ 5 fluorouracil for cancer
Ÿ Busulfan for leukaemia (cancer of the blood cells)
Ÿ Ciclosporin to prevent the rejection of organs after transplant Ÿ Disulfiram for alcoholism
Ÿ Medicines that may cause heart rhythm disturbances (so-called QT prolongation which can be seen on ECG) such as:
Ÿ certain anti-arrhythmics (medicines for heart rhythm disorders) Ÿ certain antibiotics
Ÿ medication primarily used to manage psychosis (including delusions, hallucinations, paranoia or disordered thought)
If you are not sure, talk to your doctor or pharmacist before taking Metronidazole tablets.
Metronidazole tablets with alcohol
Do not drink any alcohol while you are taking Metronidazole tablets and for 48 hours after finishing your course. Drinking alcohol while using Metronidazole tablets might cause unpleasant side effects, such as feeling sick (nausea), being sick (vomiting), stomach pain, hot flushes, very fast or uneven heartbeat (palpitations) and headache.
Pregnancy and breast-feeding
Ask your doctor or pharmacist for advice before taking Metronidazole tablets if:
Ÿ You are pregnant, might become pregnant or think you may be pregnant. Metronidazole should not be taken during pregnancy unless considered absolutely necessary.
Ÿ It is better not to take metronidazole if you are breast-feeding. This is because small amounts may pass into the mother's milk.
If you are pregnant or breast-feeding, think you may be pregnant or are planning to have a baby, ask your doctor or pharmacist for advice before taking this medicine.
Driving and using machines
While using Metronidazole tablets you may feel dizzy or experience vertigo (spinning sensation), confusion, hallucinations (seeing or hearing things that are not there), convulsions (fits) or temporary eyesight problems (such as blurred or double vision). If this happens, do not drive or use any machinery or tools.
Tests
Your doctor may wish to carry out some tests if you have been using this medicine for more than 10 days.
If you are going to have a blood test, tell the doctor or nurse performing the test that you are using Metronidazole tablets. Metronidazole tablets can affect the results of some blood tests.
If you have any further questions on the use of this medicine, ask your doctor or pharmacist.
3. How to take Metronidazole tablets
Always take this medicine exactly as your doctor or pharmacist has told you. It is important to finish a full course of treatment. The length of a course will depend on your needs and the illness being treated. Check with your doctor or pharmacist if you are not sure.
Taking this medicine
Ÿ Swallow the tablets whole with a drink of water.
Ÿ Do not crush or chew the tablets.
Ÿ Take these tablets during or just after a meal.
Ÿ The dose of Metronidazole tablets will depend on your needs and the illness being treated.
Ÿ The length of your treatment will depend on the type of illness you have and how bad it is.
The recommended dose is:
To treat bacterial infection
Adults
Ÿ The initial dose is 800 mg.
Ÿ After 8 hours take another dose of 400 mg and repeat this dose every 8 hours.
Children
Ÿ Your doctor will work out how much your child should take depending on their weight.
Ÿ Repeat the dose every 8 hours.
Ÿ If your child is a baby under 8 weeks of age, your doctor will give them one daily dose or two separate doses 12 hourly.
To prevent infections from happening after surgery
Adults
Ÿ Start taking Metronidazole tablets 24 hours before your operation. Ÿ Take 400 mg of metronidazole every 8 hours.
Ÿ After the operation you may be given metronidazole either through a drip into a vein or rectally as a suppository until you are able to take tablets again.
Children
Ÿ Give your child Metronidazole tablets 1-2 hours before their operation. Ÿ Your doctor will work out how much your child should take depending on their weight.
Ÿ After the operation your child may be given metronidazole either through a drip into a vein or rectally as a suppository until they are able to take tablets again.
Other types of infections
For treatment of other infections caused by parasites and some bacteria your doctor will decide how much metronidazole you need to take and how often. This will depend on your illness and how bad it is. The pharmacist's label on the packaging will tell you how many tablets to take and how often to take them.
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People having kidney dialysis
Kidney dialysis removes metronidazole from your blood. If you are having kidney dialysis you must take this medicine after your dialysis treatment.
People with liver problems
Your doctor may tell you to use a lower dose or to take the medicine less often.
If you take more Metronidazole tablets than you should
If you take more Metronidazole tablets than you should, tell your doctor or go to your nearest hospital casualty department straight away. Take the pack and any tablets left with you. This is so the doctor knows what you have taken.
If you forget to take Metronidazole tablets
If you forget to take a dose of Metronidazole tablets, take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose. Do not take a double dose to make up for a forgotten dose.
If you stop taking Metronidazole tablets
You should only stop taking Metronidazole tablets if your doctor tells you to. It is essential to take the medicine and not to stop and start as this could cause unwanted side effects.
If you have any further questions on the use of this medicine, ask your doctor or pharmacist.
4. Possible side effects
Like all medicines, this medicine can cause side effects, although not everybody gets them.
Stop taking Metronidazole tablets and see a doctor or go to a hospital straight away if you notice any of the following serious side effects – you may need urgent medical treatment:
Ÿ You have an allergic reaction. The signs may include: swelling of the
hands, feet, ankles, face, lips or throat which may cause difficulty in swallowing or breathing, an itchy, lumpy rash (hives) or nettle rash (urticaria).
Ÿ A serious but very rare side effect is a brain disease (encephalopathy).
Symptoms vary but you might get a fever, stiff neck, headache or see or hear things that aren't there. You might also have problems using your arms and legs, problems with speaking or feel confused. Ÿ You develop skin rashes including Stevens-Johnson syndrome or toxic
epidermal necrolysis. These can appear as reddish target-like spots or circular patches often with central blisters on the trunk, skin peeling, ulcers of the mouth, throat, nose, genitals and eyes and can be preceded by fever and flu-like symptoms. Stop using Metronidazole tablets if you develop these symptoms and contact your doctor or seek medical attention immediately. See section 2.
Ÿ You develop a red, scaly widespread rash with bumps under the skin
and blisters accompanied by fever at the initiation of treatment (acute generalised exanthematous pustulosis). Stop using Metronidazole tablets if you develop these symptoms and contact your doctor or seek medical attention immediately. See section 2.
Ÿ Yellowing of the skin and eyes. This could be due to a liver problem
(jaundice).
Ÿ Unexpected infections, mouth ulcers, bruising, bleeding gums, or severe
tiredness. This could be caused by a blood problem.
Ÿ Severe stomach pain which may reach through to your back
(pancreatitis).
Tell your doctor or pharmacist if any of the following side effects get serious or lasts longer than a few days, or if you notice any side effects not listed in this leaflet:
Very rare (affects less than 1 in 10,000 people)
Ÿ Fits (convulsions)
Ÿ Mental problems such as feeling confused and seeing or hearing things
that are not there (hallucinations)
Ÿ Problems with your eyesight such as blurred or double vision Ÿ Skin rash or flushing
Ÿ Headache
Ÿ Darkening of the urine
Ÿ Feeling sleepy or dizzy
Ÿ Pains in the muscles or joints
Ÿ Liver problems including life-threatening liver failure (hepatocellular liver
injury)
Not known (frequency cannot be estimated from the available data)
Ÿ Numbness, tingling, pain, or a feeling of weakness, in the arms or legs Ÿ Unpleasant taste in the mouth, furred tongue
Ÿ Feeling sick (nausea), being sick (vomiting), upset stomach, stomach
pain or diarrhoea
Ÿ Loss of appetite
Ÿ Fever
Ÿ Feeling depressed
Ÿ Pain in your eyes (optic neuritis)
Ÿ A group of symptoms together including: fever, nausea, vomiting,
headache, stiff neck and extreme sensitivity to bright light. This may be caused by an inflammation of the membranes that cover the brain and spinal cord (meningitis)
Ÿ Hearing impairment/hearing loss
Ÿ Ringing in the ears (tinnitus)
Ÿ Vertigo (spinning sensation)
Ÿ You get a rash or skin discolouration with or without raised areas which
often reoccurs at the same location each time the drug is taken Ÿ Acute liver failure in patients with Cockayne Syndrome (see section 2
'Warnings and precautions')
Ÿ Heart rhythm disturbances (so-called QT prolongation which can be
seen on ECG), particularly when Metronidazole tablets are used with other medicines that may cause heart rhythm disturbances
Reporting of side effects
If you get any side effects, talk to your doctor, pharmacist or nurse. This includes any possible side effects not listed in this leaflet. You can also report side effects directly via the Yellow Card Scheme at: www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects you can help provide more information on the safety of this medicine.
5. How to store Metronidazole tablets
Keep this medicine out of the sight and reach of children.
No special storage conditions are required.
Do not use this medicine after the expiry date which is stated on the pack. The expiry date refers to the last day of that month.
Do not throw away medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment.
6. Contents of the pack and other information What Metronidazole tablets contain
Each tablet contains 200 mg or 400 mg of metronidazole as the active substance.
The other ingredients are anhydrous calcium hydrogen phosphate (E341), pregelatinized maize starch, povidone (PVP K30) (E1201), maize starch, crospovidone, cellulose microcrystalline, silica colloidal anhydrous and magnesium stearate.
The coating of the tablets contains hypromellose and polyethylene glycol 400.
What Metronidazole tablets look like and contents of the pack
Metronidazole 200 mg Tablets are white to off white, caplet shaped (approx. 14.20 mm x 5.70mm) film coated tablets, debossed with “200” on one side and plain on the other side.
Metronidazole 400 mg Tablets are white to off white, caplet shaped (approx. 17.00mm x 6.00mm) film coated tablets, debossed with “400” on one side and plain on the other side.
Metronidazole 200 mg and 400 mg Tablets are available in aluminium/PVC blister pack of 14, 15, 21 and 100 tablets.
Not all pack sizes may be marketed.
Marketing Authorisation Holder
Dawa Limited,
5 Sandridge Close,
Harrow, Middlesex,
HA1 1XD, UK.
Manufacturer
Drugsrus Limited,
5 Sandridge Close,
Harrow, Middlesex,
HA1 1XD, UK.
This leaflet was last updated in March 2026.
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