Consumer medicine information

Metronide 200 and Metronide 400



Brand name


Active ingredient





Consumer medicine information (CMI) leaflet

Please read this leaflet carefully before you start using Metronide 200 and Metronide 400.

What is in this leaflet

This leaflet answers some common questions about Metronide.

It does not contain all the available information. It does not take the place of talking to your doctor or pharmacist.

All medicines have risks and benefits. Your doctor has weighed the risks of you taking Metronide against the expected benefits they expect it will have for you.

If you have any concerns about taking this medicine, ask your doctor or pharmacist.

Keep this leaflet with the medicine. You may need to read it again.

What Metronide is used for

Metronide 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.

Metronide is an antibiotic that belongs to a group of medicines called nitroimidazoles.

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

Your doctor may have prescribed Metronide for another reason.

Ask your doctor if you have any questions about why Metronide has been prescribed for you. This medicine is available only with a doctor's prescription.

There is no evidence that this medicine is addictive.

Before you take Metronide

When you must not take it

Do not take Metronide if you have ever had an allergic reaction to:

  • Metronide or any other nitroimidazoles
  • any of the ingredients listed at the end of this leaflet

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.

Do not take/use Metronide if

  • 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 take 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

If you are not sure whether to start taking Metronide, talk to your doctor.

Before you start to take it

You must tell your doctor if you have any allergies to any other medicines or any other substances such as foods, preservatives or dyes.

Tell your doctor if you 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
  • you drink alcohol
    Do not drink alcohol during (and for 24 hours after stopping) treatment with Metronide.
  • you plan to become pregnant or breastfeed

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

Taking other medicines

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

Some medicines may be affected by Metronide or may affect how well it works. These include:

  • warfarin or other medicines used to prevent blood clots
  • Antabuse (R) (disulfiram), a medicine used to treat chronic alcohol dependence
  • 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
  • ciclosporin, a medicine used to prevent organ transplant rejection or to treat immune responses
  • medications containing alcohol (ethanol), e.g. some cough syrups

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 Metronide.

How to take Metronide

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

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

How much to take

The dose will vary from patient to patient. Your doctor will decide the right dose for you.

How to take Metronide tablets

Swallow Metronide tablets whole with a glass of water, preferably during or after a meal.

Do not chew the tablets.

This may help reduce the possibility of stomach upset.

How long to take it

For treating infection, Metronide tablets are usually taken for 7 days, however, your doctor may decide to reduce or extend your treatment. Your doctor will tell you how much Metronide to take.

Do not stop taking your tablets 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.

If you forget to take it

If you are taking more than a single dose of Metronide, and 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 Metronide, ask your pharmacist for some hints.

If you take too much (overdose)

Immediately telephone your doctor or Poisons Information Centre (telephone 131126) or go to Accident and Emergency at your nearest hospital if you think that you, or anyone else, has taken too much Metronide, even if there are no signs of discomfort or poisoning. You may need urgent medical attention.

If you take too many tablets you may experience vomiting and a feeling of disorientation.

While you are taking Metronide

Things you must do

Tell your doctor immediately if:

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

If you get a sore, white mouth or tongue while taking or soon after stopping Metronide 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 Metronide allows fungi/yeast to grow and the above symptoms to occur. Metronide does not work against fungi/yeast.

If you are taking Metronide 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 taking Metronide, tell your doctor as Metronide may affect the results of some laboratory tests.

Tell all doctors, dentists and pharmacists who are treating you that you are taking Metronide.

Things you must not do

Do not drink alcohol or consume any medication containing alcohol while taking Metronide and for at least one day after finishing treatment. The use of alcohol may make you feel very sick, vomit, have stomach cramps, headaches and flushing.

Do not stop taking your medicine because you are feeling better, unless advised by your doctor. If you do not take all of the medicine 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.

Do not give Metronide to anyone else, even if they have the same condition as you.

Do not use Metronide to treat any other medical complaints unless your doctor tells you to.

Things to be careful of

Be careful driving or operating machinery until you know how Metronide affects you.

Side Effects

Tell your doctor as soon as possible if you have any problems while taking Metronide, even if you do not think the problem is connected with the medicine or is not listed in this leaflet.

As with most medications, Metronide can sometimes cause unwanted side effects. If they occur, most are likely to be minor and temporary. However, some may be serious and need medical attention.

Ask your doctor or pharmacist to answer any questions you may have.

Tell your doctor or pharmacist if you notice any of the following and they worry you:

  • oral thrush - white, furry, sore or inflamed tongue and mouth
  • vaginal thrush - sore and itchy vagina and/or discharge
  • nausea, which may be accompanied by headache, loss of appetite, and vomiting
  • diarrhoea, stomach discomfort, abdominal cramping or constipation, strange taste in mouth
  • convulsions, dizziness, weakness, feeling of incoordination or uncoordinated movements
  • confusion, irritability, depression or sleeplessness
  • skin rashes, flushing, itching
  • stuffy nose, dry mouth, nasal congestion, dryness of the mouth (or vagina or vulva)
  • unusual urination patterns (e.g. difficulty in passing urine, large amounts of urine, incontinence, or pus in urine)
  • joint pain
  • eye problems, including blurred or double vision
  • hearing problems
  • yellowing of the skin or eyes, which may be jaundice

If you have been on prolonged Metronide therapy, and experience any unusual numbness of the feet or hands, stop taking Metronide, and tell your doctor immediately.

Other side effects not listed above may also occur in some patients.

Tell your doctor as soon as possible if you notice any other effects.

Do not be alarmed by this list of possible side effects. You may not experience any of them.

After taking Metronide


Keep Metronide tablets in the blister pack until it is time to take them. If you take the tablets out of the blister pack, they may not keep well.

Keep Metronide tablets in a cool dry place where the temperature stays below 30°C.

Do not store them or any other medicine in the bathroom or near a sink.

Do not leave your medicine in the car or on windowsills. Heat and dampness can destroy some medicines.

Keep your medicine where children cannot reach it. A locked cupboard at least one-and-a-half metres above the ground is a good place to store medicines.


If your doctor tells you to stop taking Metronide, or the medicines have passed their expiry date, ask your pharmacist what to do with any medicine that is left over.

Product Description

What it looks like

Metronide tablets come in two strengths:

  • Metronide 200 mg -: round, white, with a breakline, marked "MTZ 200" on one side. A box contains 21 tablets
  • Metronide 400 mg -: round, white, with a breakline, marked "MTZ 400" on one side. A box contains 21 tablets


Active ingredient:

Metronide 200 - 200 mg metronidazole/tablet

Metronide 400 - 400 mg metronidazole/tablet

Inactive ingredients:

Metronide 200 mg and 400 mg tablets also contain calcium hydrogen phosphate, maize starch, povidone, macrogol 400, hypromellose, magnesium stearate and purified talc (400 mg only).


Metronide 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 April 2020.

Australian Registration Numbers:

Metronide 200mg tablet: AUST R 160173

Metronide 400mg tablet: AUST R 160175


Published by MIMS June 2020


Brand name


Active ingredient





1 Name of Medicine


2 Qualitative and Quantitative Composition

Metronide 200 and Metronide 400 tablets contain 200 mg and 400 mg metronidazole respectively.
For the full list of excipients, see Section 6.1 List of Excipients.

3 Pharmaceutical Form

200 mg tablets: Round, white to off-white, one face impressed with 'MTZ 200' and a breakline on the other.
400 mg tablets: Round, white to off-white, one face impressed with 'MTZ 400' and a breakline on the other.

4 Clinical Particulars

4.1 Therapeutic Indications

Anaerobic infections.

Treatment of infections in which anaerobic bacteria have been identified or are suspected as pathogens, particularly Bacteroides fragilis and other species of bacteroides, and other species such as fusobacteria, eubacteria, clostridia and anaerobic streptococci. Metronide has been used successfully in septicaemia; bacteraemia; brain abscess; necrotising pneumonia; osteomyelitis; puerperal sepsis; pelvic abscess; pelvic cellulitis; postoperative wound infections.


Metronidazole is inactive against aerobic and facultative anaerobic bacteria.

Other indications.

Oral treatment of urogenital trichomoniasis in the female (trichomonal vaginitis) and in the male, and for the treatment of bacterial vaginosis. The male consort of females suffering from urogenital trichomoniasis should be treated concurrently; all forms of amoebiasis (intestinal and extraintestinal disease and that of symptomless cyst passers); giardiasis; acute ulcerative gingivitis.

4.2 Dose and Method of Administration

A maximum of 4 g should not be exceeded during a 24 hour period. Dosages should be decreased in patients with severe hepatic disease; plasma metronidazole levels should be monitored.
In elderly patients the pharmacokinetics of metronidazole may be altered and, therefore, monitoring of serum levels may be necessary to adjust the metronidazole dosage accordingly.


(Summarised in Table 1.)
The tablets should be swallowed, without chewing, with a draught of water. It is recommended that the tablets be taken during or after a meal. Metronide tablets may be given alone or concurrently with other bacteriologically appropriate antibacterial agents.
Treatment for 7 days should be satisfactory for most patients but, depending on clinical and bacteriological assessment, the clinician might decide to prolong treatment, e.g. for the eradication of infection from site which cannot be drained or are liable to endogenous recontamination by anaerobic pathogens from the gut, oropharynx or female genital tract.

Surgical prophylaxis.


Prevention of infection at the surgical site requires that adequate tissue concentration of the drug should have been achieved at the time of surgery. The doses and route of administration should be selected in this case to achieve this objective.
As an oral ingestion is often prohibited 12 hours or longer before surgery, and it may not be practical for a variable period following surgery, tablets are not considered to be an appropriate formulation for prophylactic use. However, if oral intake is not contraindicated and is feasible following surgery, 400 mg may be taken one to two hours before surgery and repeated every eight hours for 24 hours.
The corresponding dose for children under 12 years is 100 to 200 mg for 1 to 7 years, and 200 to 400 mg for 7 to 12 years one to two hours before surgery, repeated every eight hours for 24 hours.

4.3 Contraindications

1. Patients with evidence of or a history of blood dyscrasias should not receive the drug since upon occasion a mild leucopenia has been observed during its administration. However, no persistent haematological abnormalities have been observed in animals or clinical studies.
2. Active organic disease of the central nervous system.
3. Hypersensitivity to metronidazole and other imidazoles.

4.4 Special Warnings and Precautions for Use


Alcoholic beverages and drugs containing alcohol should not be consumed by patients being treated with metronidazole and for at least a day after treatment as nausea, vomiting, abdominal cramps, headaches, tachycardia and flushing may occur. There is the possibility of a disulfiram-like (Antabuse) effect reaction.


Candida overgrowth in the gastrointestinal or genital tract may occur during metronidazole therapy and require treatment with a candidacidal drug.

Cockayne syndrome.

Cases of severe hepatotoxicity/acute hepatic failure, including cases with a fatal outcome with very rapid onset after treatment initiation in patients with Cockayne syndrome have been reported with products containing metronidazole for systemic use. In this population, metronidazole should therefore be used after careful benefit risk assessment and only if no alternative treatment is available. Liver function tests must be performed just prior to the start of therapy, throughout and after end of treatment until liver function is within normal ranges, or until the baseline values are reached. If the liver function tests become markedly elevated during treatment, the drug should be discontinued.
Patients with Cockayne syndrome should be advised to immediately report any symptoms of potential liver injury to their physician and stop taking metronidazole.

Severe bullous skin reactions.

Cases of severe bullous skin reactions such as Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN) or acute generalised exanthematous pustulosis (AGEP) have been reported with metronidazole (see Section 4.8 Adverse Effects (Undesirable Effects)). If symptoms or signs of SJS, TEN or AGEP are present, metronidazole treatment must be immediately discontinued.

Long-term therapy.

If metronidazole is to be administered for more than 10 days, it is recommended that haematological tests, especially total and differential leucocyte counts, be carried out regularly and that patients be monitored for adverse reactions, such as peripheral or central neuropathy (such as paresthesia, ataxia, dizziness, vertigo, convulsive seizures). If leucopenia or abnormal neurological signs occur, the drug should be discontinued immediately.

Surgical drainage.

Use of metronidazole does not obviate the need for aspirations of pus whenever indicated.

Nervous system.

Metronidazole should be used with caution in patients with active or chronic severe peripheral and central nervous system diseases due to the risk of neurological damage.
Patients should be warned about the potential for confusion, dizziness, hallucinations, convulsions or transient visual disorders and advised not to drive or use machinery if these symptoms occur.

Suicidal ideation.

Cases of suicidal ideation with or without depression have been reported during treatment with metronidazole. Patients should be advised to discontinue treatment and contact their healthcare provider immediately if they experience psychiatric symptoms during treatment.

Use in renal impairment.

In patients on twice weekly haemodialysis, metronidazole and its major active metabolite are rapidly removed during an 8 hour period of dialysis, so that the plasma concentration quickly falls below the therapeutic range. Hence, a further dose of metronidazole would be needed after dialysis to restore an adequate plasma concentration. In patients with renal failure the half-life of metronidazole is unchanged, but those of its major metabolites are prolonged 4-fold or greater. The accumulation of the hydroxy metabolite could be associated with side effects and measurement of its plasma concentration by high pressure liquid chromatography (HPLC) has been recommended.

Use in hepatic impairment.

No information available. As metronidazole is partly metabolised in the liver, caution should be exercised in patients with impaired liver function or hepatic encephalopathy.
Metronidazole may interfere with certain chemical analysis of serum aspartate transaminase (AST), alanine transaminase (ALT), lactate dehydrogenase (LDH), triglycerides and hexokinase glucose to give abnormally low values.

Use in the elderly.

See Section 4.2 Dose and Method of Administration.

Paediatric use.

See Section 4.2 Dose and Method of Administration.

Effects on laboratory tests.

No data available.

4.5 Interactions with Other Medicines and Other Forms of Interactions

1. Metronidazole enhances the activity of warfarin, and if metronidazole is to be given to patients receiving this or other anticoagulants, the dosages of the latter should be recalibrated. There is an increased haemorrhagic risk caused by decreased hepatic metabolism. Prothrombin times should be monitored as should anticoagulant activity.
2. The simultaneous administration of drugs that induce microsomal liver enzymes, such as phenytoin or phenobarbital (phenobarbitone), may accelerate the elimination of metronidazole, resulting in reduced plasma levels; impaired clearance of phenytoin has also been reported.
3. The simultaneous administration of drugs that decrease microsomal liver enzyme activity, such as cimetidine, may prolong the half-life and decrease plasma clearance of metronidazole.
4. In patients stabilised on relatively high doses of lithium, short-term metronidazole therapy has been associated with elevation of serum lithium and, in a few cases, signs of lithium toxicity. Serum lithium and serum creatinine levels and electrolytes should be obtained several days after beginning metronidazole to detect any increase that may precede clinical symptoms of lithium intoxication.
5. Psychotic reactions have been reported in patients who were using metronidazole and disulfiram concurrently. Metronidazole should not be given to patients who have taken disulfiram within the last two weeks.
6. Carmustine, cyclophosphamide monohydrate. Metronidazole should be used with caution in patients receiving these drugs.
7. There is a risk of ciclosporin serum levels increasing when it is used in combination with metronidazole. Serum ciclosporin and serum creatinine should be closely monitored when coadministration is necessary.
8. Metronidazole used in combination with 5-fluorouracil may lead to reduced clearance of 5-fluorouracil, resulting in increased toxicity.
9. Alcoholic beverages and drugs containing alcohol should not be consumed during metronidazole therapy and for at least one day afterwards because of the possibility of a disulfiram-like (Antabuse effect) reaction (flushing, vomiting, tachycardia).
10. Plasma levels of busulfan may be increased by metronidazole, which may lead to severe busulfan toxicity.

4.6 Fertility, Pregnancy and Lactation

Effects on fertility.

No data available.
(Category B2)
Metronidazole should not be given in the first trimester of pregnancy as it crosses the placenta and enters foetal circulation rapidly. As its effects on human foetal organogenesis are not known, its use in pregnancy should be carefully evaluated. Although it has not been shown to be teratogenic in either human or animal studies, such a possibility cannot be excluded.
Use of metronidazole for trichomoniasis in the second and third trimesters should be restricted to those in whom local palliative treatment has been inadequate to control symptoms.
Metronidazole is secreted in breast milk (see Section 5.2 Pharmacokinetic Properties). In view of its tumorigenic and mutagenic potential (see Section 5.3 Preclinical Safety Data), breastfeeding is not recommended.

4.7 Effects on Ability to Drive and Use Machines

Patients should be warned about the potential for confusion, dizziness, vertigo, hallucinations, convulsions or transient visual disorders and advised not to drive or use machinery if these symptoms occur. See Section 4.4 Special Warnings and Precautions for Use; Section 4.8 Adverse Effects (Undesirable Effects).

4.8 Adverse Effects (Undesirable Effects)

Gastrointestinal effects.

When given orally, metronidazole is well tolerated. The most common adverse reactions refer to the gastrointestinal tract, particularly nausea, sometimes accompanied by headache, anorexia and occasionally vomiting, diarrhoea, epigastric pain or distress and abdominal cramping; constipation, oral mucositis and taste disorders have also been reported. A metallic, sharp, unpleasant taste is not unusual. Cases of pancreatitis, which abated on withdrawal of the drug, have been reported. Crohn's disease patients are known to have an increased incidence of gastrointestinal and certain extraintestinal cancers. If patients receiving metronidazole drink alcoholic beverages, they may experience abdominal distress, nausea, vomiting, flushing or headache. A modification of the taste of alcoholic beverages has also been reported.
Furry tongue, tongue discolouration, glossitis and stomatitis have occurred; these may be associated with a sudden overgrowth of Candida which may occur during effective therapy.

Body as a whole.

Hypersensitivity reactions include rash, pruritus, flushing, urticaria, fever, angioedema and anaphylactic shock. Nasal congestion and dryness of the mouth have been reported. Mild erythematous eruptions have been experienced as have fleeting joint pains sometimes resembling serum sickness. Pustular eruptions and acute generalised exanthematous pustulosis have been reported. Fixed drug eruption has been reported. Stevens-Johnson syndrome and toxic epidermal necrolysis have also been reported.


Increase in liver enzymes (AST, ALT, alkaline phosphatase), cholestatic or mixed hepatitis and hepatocellular liver injury, sometimes with jaundice, have been reported.
Cases of liver failure requiring liver transplant have been reported in patients treated with metronidazole in combination with other antibiotic drugs; all spiramycin except one case of tetracycline.


A moderate leucopenia may be observed occasionally. If this occurs, the total leucocyte count may be expected to return to normal after the course of medication is completed. One case of bone marrow depression has been reported. If profound bone marrow suppression occurs, use of metronidazole should be ceased and appropriate supportive therapy instituted. Cases of agranulocytosis, neutropenia or thrombocytopenia have been reported.

Psychiatric/CNS disorders.

Dizziness, vertigo, incoordination, headache and convulsive seizures have been reported. Psychotic disorders such as confusion and hallucinations have been reported. Depression, depressed mood, insomnia, irritability, weakness have been experienced, as has peripheral neuropathy, characterised mainly by numbness or paraesthesia of an extremity. There have been reports of encephalopathy (e.g. confusion, vertigo) and subacute cerebellar syndrome (e.g. ataxia, dysarthria, gait impairment, nystagmus and tremor), which may resolve with the discontinuation of the drug. Since persistent peripheral neuropathy has been reported in some patients receiving prolonged administration of metronidazole, such subjects should be specifically warned about these reports and should be told to stop the drug and report immediately if any neurological symptoms occur. Aseptic meningitis has been reported.
Frequency not known: vertigo.

Eye disorders.

Optic neuropathy/neuritis and transient vision disorders such as diplopia, myopia, blurred vision, decreased visual acuity and changes in colour vision have been reported.

Ear and labyrinth disorders.

Impaired hearing/hearing loss (including sensorineural) and tinnitus have been reported.

Genitourinary tract.

Proliferation of Candida also may occur in the vagina. Dryness of the vagina or vulva, pruritus, dysuria, cystitis and a sense of pelvic pressure have been reported. Very rarely dyspareunia, fever, polyuria, incontinence, decrease of libido, proctitis and pyuria have occurred in patients receiving the drug.
Instances of darkened urine have been reported and this manifestation has been the subject of special investigation. Although the pigment which is probably responsible for this phenomenon has not been positively identified, it is almost certainly a metabolite of metronidazole. It seems certain that it is of no clinical significance and may be encountered only when metronidazole is administered in higher than recommended doses.


Flattening of the T wave may be seen in ECG tracings.

Reporting suspected adverse reactions.

Reporting suspected adverse reactions after registration of the medicinal product is important. It allows continued monitoring of the benefit-risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions at (Australia) or (New Zealand).

4.9 Overdose


Overdosage with metronidazole appears to be associated with very few abnormal signs or symptoms. Disorientation, ataxia and vomiting may occur, especially after ingestion of large amounts. In case of suspected overdosages, a symptomatic and supportive treatment should be instituted.
Single oral doses of metronidazole, up to 12 g, have been reported in suicide attempts and accidental overdoses.


There is no specific antidote for metronidazole overdosage. In cases of suspected overdosage, a symptomatic and supportive treatment should be instituted.
For information on the management of overdose, contact the Poison Information Centre on 131126 (Australia) or the National Poisons Centre, 0800 POISON or 0800 764 766 (New Zealand).

5 Pharmacological Properties

5.1 Pharmacodynamic Properties

Pharmacotherapeutic group: Antibacterials for systemic use, ATC code J01X D01.

Mechanism of action.

Specific bactericidal activity against important obligate anaerobes.
Metronidazole is effective in vitro against several species of anaerobic bacteria, particularly Bacteroides fragilis and other species of bacteroides, and other species such as fusobacteria, eubacteria, clostridia, and anaerobic streptococci. The MIC for most susceptible anaerobes is < 6.2 microgram/mL.


Metronidazole is inactive against aerobic and facultative anaerobic bacteria.
Metronidazole is active against a wide range of pathogenic microorganisms notably Trichomonas vaginalis and other trichomonads, Entamoeba histolytica, Giardia lamblia, Balantidium coli and the causative organisms of acute ulcerative gingivitis.

Clinical trials.

No data available.

5.2 Pharmacokinetic Properties


Maximum concentrations occur in the serum 1 to 2 hours after oral administration and at the end of the infusion after intravenous administration. Traces are detected after 24 hours. The biological half-life of oral and intravenous metronidazole has been determined as 6 to 7 and 7.3 hours, respectively.


Metronidazole is widely distributed in body tissues and fluids. It diffuses across the blood brain barrier and placenta and is found in the breast milk of nursing mothers in concentrations equivalent to those in serum.
It is not protein bound to any significant degree.


No data available.


Most of the dose is excreted in the urine as metronidazole and its metabolites, including acid oxidation products and glucuronides.

5.3 Preclinical Safety Data


In studies on the mutagenic potential of metronidazole, the Ames test was positive while several nonbacterial tests in animals were negative. In the patients with Crohn's disease, metronidazole increased the chromosome abnormalities in circulating lymphocytes. The use of metronidazole for longer treatment than usually required should be carefully weighed (see Section 4.4 Special Warnings and Precautions for Use) and the benefit/risks should, therefore, be carefully assessed in each case particularly in relation to the severity of the disease and the age of the patient.


Metronidazole been shown to be tumorigenic and carcinogenic in rodents.



6 Pharmaceutical Particulars

6.1 List of Excipients

Tablet: magnesium stearate, calcium hydrogen phosphate, povidone, hypromellose, maize starch, macrogol 400 and purified talc (400 mg tablets only).

6.2 Incompatibilities

Incompatibilities were either not assessed or not identified as part of the registration of this medicine.

6.3 Shelf Life

In Australia, information on the shelf life can be found on the public summary of the Australian Register of Therapeutic Goods (ARTG). The expiry date can be found on the packaging.

6.4 Special Precautions for Storage

Store below 30°C. Protect from light.

6.5 Nature and Contents of Container

PVC/PVDC/Al blister packs.
200 mg tablets: Pack sizes: 21s*.
400 mg tablets: Pack sizes: 5s, 21s*.
* Marketed pack size.

6.6 Special Precautions for Disposal

In Australia, any unused medicine or waste material should be disposed of by taking to your local pharmacy.

6.7 Physicochemical Properties

Metronidazole is a 1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole. It appears as white to brownish cream crystals with melting point of 159 to 162°C. Metronidazole in a saturated aqueous solution has a pH of between 6 and 7.5. Solubility at 20°C (g/100 mL): 1 in water; 0.5 in ethanol; 0.4 in chloroform; slightly soluble in ether, soluble in dilute acids.

Chemical structure.

CAS number.


7 Medicine Schedule (Poisons Standard)

Schedule 4. Prescription Only Medicine.

Summary Table of Changes