Patient leaflet - Metronidazole 5 mg / ml solution for infusion
1. What Metronidazole is and what it is used for
Metronidazole belongs to a group of medicines known as antibiotics and is used to treat severe infections caused by bacteria that can be killed by the active substance metronidazole.
In general this medicine is suitable for adults, adolescents, children and newborns. Your doctor will decide if the solution is suitable for your individual situation.
You may be given Metronidazole for the treatment of any of the following diseases:
- Infections of the blood, brain, lung, bones, genital tract, pelvic area and stomach
If required, your treatment may be supplemented by other antibiotics. Metronidazole may be given as a preventive measure prior to operations associated with a higher risk of infection with what are known as anaerobic bacteria, mainly in gynaecology or surgery on stomach and gut.
2. What you need to know before you take Metronidazole
Do not take Metronidazole
if you are allergic (hypersensitive) to metronidazole, other similar
substances or any of the other ingredients of Metronidazole (listed in section 6).
Warnings and precautions
Talk to your doctor, pharmacist or nurse before taking Metronidazole if you have:
- severe liver damage,
- a blood formation disorder or
- a disease of brain, spinal cord or nerves
Therefore, your doctor will very carefully determine whether you should be treated with Metronidazole.
If convulsive fits or any other nerve problems or symptoms (e.g. numbness in limbs) become apparent during therapy, your treatment will promptly be revised.
Especially with prolonged metronidazole treatment or if you are immunocompromised, an imbalance of the intestinal flora may occur. Treatment must be stopped or revised immediately if you get severe diarrhoea which may be due to a severe large bowel disease called “pseudomembranous colitis” (see also section 4.).
As prolonged use of metronidazole may impair blood formation (see section “Possible side effects”), your blood counts will be monitored during treatment.
If you received this medicine your urine may be darkened. Cases of severe liver toxicity/acute liver failure, including cases with a fatal outcome, in patients with Cockayne syndrome have been reported with product containing metronidazole.
If you are affected by Cockayne syndrome, your doctor should also monitor your liver function frequently while you are being treated with metronidazole and afterwards.
Tell your doctor immediately and stop taking metronidazole if you develop:
Stomach pain, anorexia, nausea, vomiting, fever, malaise, fatigue,
jaundice, dark urine, putty or mastic-coloured stools or itching.
Serious reactions, including Stevens-Johnson syndrome, toxic
epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (DRESS), acute generalized exanthematous pustulosis (AGEP) have been reported in association with Metronidazole 5 mg/ml treatment. Stop using Metronidazole 5 mg/ml and seek medical attention immediately if you notice any of the symptoms related to these serious skin reactions described in section 4. Treatment with Metronidazole should not usually be continued for longer than 10 days; the treatment period will only be extended in exceptional circumstances and if absolutely necessary. Repeat-therapy with metronidazole will be restricted to cases where this is absolutely necessary. In such a case, you will be monitored particularly carefully.
Other medicines and Metronidazole
Please tell your doctor or pharmacist if you are taking or have recently taken any other medicines, including medicines obtained without a prescription.
Medicines that may cause heart rhythm disturbances
Tell your doctor if you are taking any medicines that can cause a heart rhythm disorder (the so-called QT interval prolongation that can be seen on an ECG), such as certain antiarrhythmics (medicines to treat heart rhythm disorders like e.g., amiodarone) and certain antibiotics (like e.g., ciprofloxacin).
When you receive this medicine, your heart function should be monitored.
You should see your doctor if you notice any heart function abnormalities, dizziness or fainting.
Barbiturates (the active substance in sleeping pills)
The duration of action of metronidazole is reduced by phenobarbital; your metronidazole dose may therefore have to be increased.
Busulfan
Metronidazole should not be given to patients receiving busulfan because in that case toxic effects are more likely to occur.
Carbamazepine (a drug for the treatment of epilepsy)
This combination also warrants caution because metronidazole may increase the duration of action of carbamazepine.
Cimetidine (a drug for the treatment of stomach disorders)
Cimetidine may reduce the elimination of metronidazole in isolated cases and subsequently leads to increased serum metronidazole concentrations.
Coumarin derivatives (drugs that inhibit blood clotting)
Metronidazole may enhance the blood clotting inhibition brought about by coumarins. So, if you are taking a medicine that inhibits blood clotting (for example warfarin), you may need less of it during treatment with metronidazole.
Cyclosporin (a drug used to suppress undesirable immune responses)
When cyclosporin is given together with metronidazole, the blood levels of cyclosporin may increase; your doctor will therefore have to adjust your cyclosporin dose as appropriate. In addition your kidney function will be monitored.
Disulfiram (used in alcohol withdrawal therapy)
If you are taking disulfiram, you must not be given metronidazole, or disulfiram must be stopped. Combined use of these two drugs may lead to states of confusion up to the point of a serious mental disorder (psychosis).
Drugs containing alcohol
Please refer to section ‘Using Metronidazole’ with food and drink.
Fluorouracil (an anticancer drug)
The daily dose of Fluorouracil may have to be reduced when giving it together with Metronidazole because metronidazole may lead to an increase of the blood level of Fluorouracil.
Lithium (used to treat mental illness)
Treatment with lithium preparations requires particularly careful monitoring during treatment with metronidazole, and the dose of the lithium preparation may need to be re-adjusted. Lithium treatment should be tapered or withdrawn before administration of metronidazole.
Mycophenolate mofetil (used for the prevention of rejection reactions after organ transplant)
Its effect may be weakened by metronidazole, so careful monitoring of the effect of mycophenolate mofetil is recommended.
Phenytoin (a drug for the treatment of epilepsy)
If you are taking phenytoin, your doctor will treat you with metronidazole only with caution because metronidazole may increase the duration of action of phenytoin. On the other hand, phenytoin may reduce the effect of metronidazole.
Tacrolimus (used to suppress unwanted immune reactions)
The blood levels of this agent and your kidney function should be checked when starting and stopping treatment with metronidazole.
Metronidazole with food, drink and alcohol Alcohol
You must not drink any alcoholic beverages or drugs containing alcohol while you are being given metronidazole and up to 48 hours afterwards because this may cause you to feel very unwell with symptoms such as palpitations, flushing, sweating, dizziness and vomiting.
Pregnancy breast-feeding and fertility
If you are pregnant or breast-feeding, think you may be pregnant or are planning to have a baby, ask your doctor for advice before taking this medicine.
Pregnancy
If you are pregnant, your doctor will not treat you with metronidazole unless she/he considers this absolutely necessary.
Breast-feeding
You should not breast-feed during treatment with metronidazole and not resume nursing for another 2–3 days thereafter because metronidazole passes into breast milk.
Fertility
Animal studies only indicate a potential negative influence of metronidazole on the male reproductive system if high doses lying well above the maximum recommended dose for humans were administered.
Driving and using machines
While taking Metronidazole you may feel sleepy, dizzy, confused, see or hear things that are not there (hallucinations), have fits (convulsions) or temporary eyesight problems (such as blurred or double vision). If this happens, do not drive or use any machinery or tools.
Metronidazole contains sodium
This medicine contains 322 mg sodium (main component of cooking/ table salt) in each 100 ml.
This is equivalent to 16.1 % of the recommended maximum daily dietary intake of sodium for an adult.
Package leaflet: Information for the user
Metronidazole 5 mg/ml solution for infusion
Metronidazole
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Metronidazole 5 mg/ml solution for infusion
Metronidazole
The following information is intended for healthcare professionals only:
This solution can be diluted prior to administration with sodium chloride 0.9 % w/v or glucose 5 % w/v solutions for infusion. For dilution procedures the usual precautions of asepsis must be followed.
Posology and method of administration
The dosage is adjusted according to the patient’s individual response to therapy, her/his age and body weight and according to nature and severity of the disease.
The following dosage guidelines should be followed: Adults and adolescents
Treatment of anaerobic infections
500 mg (100 ml) every 8 hours. Alternatively 1000 mg – 1500 mg may be given daily as a single dose.
The duration of therapy is dependent on the effect of the treatment. In most cases a treatment course of 7 days will be sufficient. If clinically indicated, treatment may be continued beyond this time although a duration of 10 days should not normally be exceeded. (See also section 4.4.)
Prophylaxis against post-operative infection caused by anaerobic bacteria:
500 mg, with administration completed approximately one hour before surgery. The dose is repeated after 8 and 16 hours.
Elderly
Caution is advised in the elderly, particularly at high doses, although there is limited information available on modification of dosage.
Paediatric population
Treatment of anaerobic infections
Children > 8 weeks to 12 years of age:
The usual daily dose is 20 – 30 mg per kg BW per day as a single dose or divided into 7.5 mg per kg BW every 8 hours. The daily dose may be increased to 40 mg per kg BW, depending on the severity of the infection.
Neonates and infants < 8 weeks of age:
15 mg per kg BW as a single dose daily or divided into 7.5 mg per kg BW every 12 hours.
In newborns with a gestational age < 40 weeks, accumulation of metronidazole can occur during the first week of life; therefore the concentrations of metronidazole in serum should preferably be monitored after a few days of therapy.
Duration of treatment is usually 7 days.
3. How to take Metronidazole
Dosage
Dosage depends on the nature and severity of your illness, your age and body weight, and your individual response to treatment.
The following dosages are usually prescribed:
Adults and adolescents
Treatment of infections:
Adults
You will be given 100 ml of the medicine (500 mg of metronidazole) every 8 hours.
In most cases treatment will take 7 days. Only exceptionally treatment may be continued beyond this time, although a duration of 10 days should not normally be exceeded.
The dose will be the same for patients with kidney diseases. For patients with liver diseases, lower doses may be required. If you were treated by artificial kidney your doctor will schedule your infusion after dialysis has been finished. No routine dose adjustment is necessary.
Prevention of infections that might occur after operations When used for prevention of infection in surgery, you may be given 500 mg of the medicine before the operation. The dose will be repeated 8 and 16 hours after the operation.
Elderly
Your doctor will give you this medicine only with special caution.
Children
Dosing in children is based on body weight (BW).
Treatment of infections:
Age Dosage
8 weeks to
12 years
20 – 30 mg of metronidazole per kg BW per day as a single dose or divided into 7.5 mg of metronidazole per kg BW every 8 hours. The daily dose may be increased to 40 mg of metronidazole per kg BW if infection is severe. Under 8 weeks 15 mg of metronidazole per kg BW as a single
dose daily or divided into 7.5 mg per kg BW every 12 hours.
Newborns of less
than 40 weeks
gestational age
As metronidazole may accumulate in these patients during the first week of life, the concentration of metronidazole in the blood will be checked after a few days of treatment. Usually treatment will take 7 days.
Prevention of infections that might occur after operations: Age Dosage
Less than 12 years 20 – 30 mg of metronidazole per kg BW as a
single dose given 1 – 2 hours before surgery Newborns of less
than 40 weeks
gestational age
10 mg of metronidazole per kg BW as a single dose before surgery
Method of administration and duration of treatment
Metronidazole is administered through a drip directly into a vein (intravenous infusion).
The infusion of one bottle usually takes 60 minutes, but it should not be done within less than 20 minutes.
This medicine may be diluted in a suitable solution for infusion. The entire metronidazole treatment period is usually 7 days and must not exceed 10 days unless this is absolutely necessary (see also “Take special care with Metronidazole”). If you are concurrently receiving other antibiotics your doctor will give you those medicines separately.
If you take more Metronidazole than you should
Undesirable effects, as described in the next section, may occur as signs or symptoms of an overdose. Single oral doses of metronidazole, up to 12 g have been reported in suicide attempts and accidental overdoses.
Symptoms were limited to vomiting, ataxia and slight disorientation. There is no known specific antidote or specific treatment of a massive overdose, but metronidazole can be removed by dialysis (that is treatment with artificial kidney) from the body.
4. Possible side effects
Like all medicines, Metronidazole can cause side effects, although not everybody gets them.
Side effects occur mostly at high doses or with prolonged use.
Talk to your doctor straight away if you notice any of the following side effects:
Rare (may affect up to 1 in 1,000 people):
Severe persistent diarrhoea (possibly a symptom of a severe bowel
infection called pseudomembranous colitis, see below) Emergency management of pseudomembranous enterocolitis In the event of severe persistent diarrhoea, you must promptly inform your doctor because this may be due to pseudomembranous colitis, a serious condition that must be treated immediately. Your doctor will stop metronidazole and provide appropriate treatment.
Severe acute hypersensitivity reactions up to allergic shock
(swelling of the face, lips and airways well as low blood pressure, shortness of breath, collapse and even death)
Very rare (may affect up to 1 in 10,000 people):
White blood cell and platelet counts may decrease during
treatment (granulocytopenia, agranulocytosis, pancytopenia, thrombocytopenia). Regular monitoring of blood cell counts is necessary during prolonged use.
Hepatitis (liver inflammation), jaundice, inflammation of the
pancreas (isolated reports)
- Brain disorders, lack of coordination
Not known (frequency cannot be estimated from the available data):
Mild to moderate hypersensitivity reactions, swelling of your face,
mouth, throat and/or tongue (angioedema).
Gaze spasm, damage or inflammation of the nerves of your eyes
Reduced white blood cell, count (leucopenia), severe anaemia
(aplastic anaemia)
- Seizures, nervous disorders such as numbness, pain, furry sensation or tingling in the arms or legs
- Inflammation of the meninges (or brain lining) that is not caused by bacteria (aseptic meningitis)
- Acute liver failure in patients with Cockayne syndrome (see section 2 “Warnings and precautions”)
- hearing impairment, hearing loss
- Ringing in the ears (tinnitus)
- Skin rash, blisters, fever or other signs and symptoms of hypersensitivity reactions
- reddish non-elevated, target-like or circular patches on the trunk, often with central blisters, skin peeling, ulcers of mouth, throat, nose, genitals and eyes. These serious skin rashes can be preceded by fever and flu-like symptoms (Stevens-Johnson syndrome, toxic epidermal necrolysis).
- Widespread rash, high body temperature and enlarged lymph nodes (DRESS syndrome or drug hypersensitivity syndrome).
- A red, scaly widespread rash with bumps under the skin and blisters accompanied by fever. The symptoms usually appear at the initiation of treatment (acute generalised exanthematous pustulosis).
Other side effects include
Common (may affect up to 1 in 10 people):
- Yeasts and bacterial superinfections (e.g. genital infections)
Uncommon (may affect up to 1 in 100 people):
- Darkened urine (due to a metabolite of metronidazole)
Rare (may affect up to 1 in 1,000 people):
- Changes in ECG (electrical activity of the heart)
Very rare (may affect up to 1 in 10,000 people):
- Psychotic disorders, including states of confusion, hallucination
- Headache, dizziness, drowsiness, fever, disturbance of sight and movement, giddiness, speech defects, convulsions
- Visual disturbances, e.g. double vision, short-sightedness
- Liver function disorders (such as elevated serum levels of certain enzymes and bilirubin)
- Allergic skin reactions like itching, hives
- Joint and muscle pain
Not known (frequency cannot be estimated from the available data):
- Sickness, feeling sick, diarrhoea, inflammation of tongue or mouth, belching and bitter taste, metallic taste, pressure above the stomach, furry tongue
- Difficulty swallowing
- Reduced interest/appetite for food (anorexia)
- Sad (depressed) mood
- Sleepiness or sleeplessness, muscle twitching
- Reddening and itching of the skin (erythema multiforme)
Vein wall irritation (to the point of inflamed veins and thrombosis)
after intravenous administration, states of weakness, fever If any of the side effects gets serious, or if you notice any side effects not listed in this leaflet, please tell your doctor.
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, Website: 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
Keep this medicine out of the sight and reach of children. Do not use this medicine after the expiry date which is stated on the bag and the carton after EXP. The expiry date refers to the last day of that month.
Do not store above 25 °C.
Do not refrigerate.
Keep the bag in the original packaging (aluminium overwrap) in order to protect from light.
After first opening the medicinal product should be used immediately. Use only if the solution is clear and free of visible particles, and the bottle and closure are intact. This medicinal product is intended for single use only. Discard any unused portions.
Do not throw away any medicines via wastewater. 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 contains
The active substance is metronidazole.
Each 100 ml of solution for infusion contains 500 mg metronidazole. Each ml of solution for infusion contains 5 mg metronidazole. Other ingredients are: Sodium chloride, Disodium phosphate, Anhydrous, Citric acid, Anhydrous and Water for injections.
What Metronidazole looks like and contents of the pack
Metronidazole is a clear, colourless or slightly yellowish aqueous solution infusion.
Metronidazole is contained in polypropylene bags closed with a twist off port, inside an aluminum overwrap, containing 100 ml of solution. This medicine is marketed as individual packs or packs of 10 bags. Not all pack sizes may be marketed.
Marketing Authorisation Holder and Manufacturer
Hikma Farmacêutica (Portugal) S.A.
Estrada do Rio da Mó, nº8, 8A e 8B
Fervença
2705-906 Terrugem SNT
Portugal
This leaflet was last revised in April 2026
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Prophylaxis against postoperative infections caused by anaerobic bacteria:
Children < 12 years:
20 – 30 mg/kg BW as a single dose given 1 – 2 hours before surgery
Newborns with a gestation age < 40 weeks:
10 mg/kg BW as a single dose before surgery
Patients with renal insufficiency
Limited data are available in this population. These data do not indicate the need for dose reduction (see section 5.2.) In patients undergoing haemodialysis the conventional dose of metronidazole should be scheduled after haemodialysis on dialysis days to compensate the removal of metronidazole during the procedure.
No routine dose adjustment is necessary in patients with renal failure undergoing intermittent peritoneal dialysis (IDP) or continuous ambulatory peritoneal dialysis (CAPD).
Patients with hepatic insufficiency
As serum half-life is prolonged and plasma clearance is delayed in severe hepatic insufficiency, patients with severe liver disease will require lower doses (see section 5.2).
In patients with hepatic encephalopathy, the daily dosage should be reduced to one third and may be administered once daily (see section 4.4).
Method of administration
Intravenous use.
The contents of one bottle are to be infused slowly i.v., i.e. 100 ml max. over not less than 20 minutes, but normally over one hour. Concurrently prescribed antibiotics are to be administered separately.