June 19 2024

Indications and usage     

Metronidazole is an anti-infective drug that belongs to a group of antibiotics named nitroimidazoles.

It is used to treat infections due to parasites and bacteria against which the medicine is active. Infections treatable with metronidazole are:

lambliasis; intestinal and hepatic amoebiasis; anaerobic bacterial infections, due to Bacteroides fragilis, Clostridium perfringens and other anaerobes; and Trichomonas conditions (urethritis and vaginitis).

Medizzine recommends that you consult your doctor if you are unsure why you have been prescribed oral metronidazole.

Other ingredients of available commercial presentations:


The active ingredient is metronidazole. The other ingredients are: wheat starch (gluten content: 0.1 mg), magnesium stearate, povidone K30, hypromellose, macrogol 20,000 and purified water.

Oral suspension

The active ingredient is metronidazole. Each 5 ml (1 small teaspoonful) of the suspension contains 200 mg of metronidazole benzoate equivalent to 125 mg of metronidazole (INN). The other ingredients are: monosodium phosphate, nipagin, nipasol, magnesium aluminosilicate, anhydrous sodium saccharin, sucrose, alcohol 96°, concentrated essence of lemon oil, orange deterpenated and demineralized water.


The composition of the various presentations may vary from one country to another. We recommend you consult the information provided by your local supplier.

Important Information     

This medicine in tablets containing wheat starch as excipient. Celiac disease patients should consult their physician before use.

Oral suspension contains 600 mg/ml of sucrose, which should be taken into account in diabetic patients. Also contains ethanol as excipient, that could be a risk in patients with liver disease, alcoholism, epilepsy, and in pregnant women and children.

Before taking the drug     

Do not use oral metronidazole

If you are allergic (hypersensitive) to the active substance, to the imidazole derivatives or any of the other ingredients of the medicinal product prescribed for you <. If you think you may be allergic, ask your doctor.

Allergy symptoms may include:

- Asthma attacks with shortness of breath, audible wheezing or rapid breathing.
- More or less sudden swelling of face, lips, tongue or elsewhere in the body. It is especially critical if it affects the vocal cords.
- Hives, itching, rash
- Anaphylactic shock (loss of consciousness, paleness, sweating, etc.).

Also, you should not take this medicine:

Take special care with oral metronidazole

- If you have severe liver problems.
- If your treatment is prolonged. Your doctor may ask you to perform regularly blood tests, especially to control the number of white blood cells. Also will be closely monitored by the risk of conditions such as nerve paresthesias (tingling in hands or feet), ataxia (uncoordinated movements), dizziness and convulsions.
- If you suffer from serious chronic or acute diseases of the central or peripheral nervous system due to the potential risk of worsening.
- If you have severe kidney disorders. In this case your doctor may reduce the dose when you are not on dialysis or the drug levels in the blood are not controlled.
-This medicine may darken the color of your urine.

Remember that your doctor has prescribed this medicine only for you. Never give it to someone else.

In case of doubt, consult your doctor.

Taking other medicines

Tell your doctor or pharmacist if you are taking or have recently taken any other medicines, including herbal products or drugs obtained without a prescription.

Coadministration of metronidazole and disulfiram is not recommended because have been produced cases of mental disorders.

Beverages and medicines containing alcohol should not be consumed during metronidazole treatment until at least two days after finish it, due to the possibility of occurrence of so-called Antabuse effect, reaction characterized by flushing, vomiting and tachycardia.

Co-administration of metronidazole and oral anticoagulants (warfarin type) may increase the risk of bleeding. If metronidazole is administered while you are taking any of these drugs, you should be closely monitored by your doctor (INR).

There is higher risk of elevated blood levels of lithium (medicine for depression) and cyclosporin (medicine used to lower the body's defenses) when these drugs are coadministered with metronidazole. Hence, if coadministered, must be only under strict medical supervision.

Phenytoin and phenobarbital (AEDs) increase the elimination of metronidazole and produced lower blood levels of this last.

Metronidazole increases toxicity of fluorouracil and busulfan (medicines used to treat cancer).

Use with food and beverages

Do not drink any alcohol while you are taking metronidazole and for 48 hours after finishing your course. Drinking alcohol while using metronidazole 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.

Special physiological situations

Pregnancy and lactation

Always consult your doctor or pharmacist before taking any medicine during pregnancy or breastfeeding.

As metronidazole crosses the placental barrier and not enough data to establish its safety during pregnancy, your doctor will carefully assess the appropriateness of using this medicine during pregnancy.

Metronidazole is excreted in breast milk so its administration should be avoided during breastfeeding.


Driving and using machines

If you have any of the following side effects caused after administration of metronidazole such as confusion, dizziness, hallucinations, convulsions and transient visual disturbances must refrain from driving or operating machines.

Consult your doctor or pharmacist before taking any medicine.

How to use oral metronidazole     

Follow exactly instructions of use of oral metronidazole provided by your doctor. Consult your doctor or pharmacist when in doubt. Follow the instructions of the physician in preference to those given in this website, that may be different. Ask your doctor to explain any aspect that you do not understand, contained in the instruction leaflet that comes with the medicine.

Your doctor will tell you your daily dose and duration of treatment. Do not stop your treatment before.

Your doctor has prescribed an personalized dose for you. Depending on your response to treatment may change this conveniently

Diseases produced by triochomonas

In men (urethritis by trichomonas):

The recommended dose is 500 mg of metronidazole (2 tablets or 4 small teaspoons) per day in 2 divided doses, between meals, for 10 consecutive days. Very rarely, your doctor may increase the dose to 750 or 1,000 mg daily.

In women (urethritis and vaginitis by trichomonas):

Mixed treatment is recommended: orally, equal doses than men, and vaginal (one vaginal tablet of 500 mg) applied deeply in the vagina daily before go to bed, during 10 to 20 days.

Whether or not your partner has symptoms of infection with Trichomonas vaginalis, even if they do not give positive laboratory tests, it is necessary that it be treated with oral metronidazole.



The recommended dose is 500 mg daily.

In children (orally):

- 2 to 5 years: 250 mg/day (one oral tablet or 2 small teaspoons)
- 5 to 10 years: 375 mg/day (1 tablet and a half or 3 small teaspoons)
- 10 to 15 years: 500 mg/day (2 oral tablets or ó 4 small teaspoons)

The recommended duration of treatment is 5 consecutive days, in two doses between meals. In case of failure it may be necessary to repeat the treatment after an interval of 8 days.


- In adults it is recommended from 1.5 to 2 g per day on 3 or 4 doses.

- In children: 40-50 mg / day / kg in 3-4 doses.

The duration of treatment in the intestinal and hepatic amoebiasis is 5 to 7 days.

Anaerobic infections

- In adults: 500 mg every 8 hours
- In children: 7.5 mg/kg/8 hours

If you think that the effect of the medicine is too strong or too weak, consult your doctor.

If you have any further questions on the use of this product, ask your doctor or pharmacist.

You need to consider while taking oral metronidazole     

If you become pregnant, consult your doctor.

If a doctor prescribes to you another medication, let him know that you are taking oral metronidazole.

Check with your doctor regularly the disorder evolution that motivates the administration of oral metronidazole. Perhaps there is some reason that has prevented properly receive the indicated doses and induce misleading your doctor about treatment.

Do not restart by own initiative the treatment with oral metronidazole without first talking with your doctor, or recommend the use of this drug to another person, even if have the same symptoms you have. Nor is it advisable to interrupt or reduce the dose without considering the opinion of your doctor.

If during treatment with oral metronidazole feel unwell, consult your doctor immediately.

If you use more medicine than you should

Consult your doctor immediately or go to the emergency room of the nearest hospital carrying the medication. Accidental overdose may lead to vomiting, incoordination of movements and slight disorientation.

No specific antidote for metronidazole overdose is known. In cases where it is suspected that there has been a massive ingestion, treatment will be based on the symptoms.

If you forget to take the medicine

Take it as soon as you remember. However, if it is almost time for your next dose, skip the missed dose and continue as before.

Do not take a double dose to compensate forgotten individual doses.

If you stop taking oral metronidazole

Do not stop treatment without knowing the opinion of your doctor. The disease that causes drug intake can worsen.

If you have any further questions on the use of this product, ask your doctor or pharmacist.

Side Effects of oral metronidazole     

Like all medicines, oral metronidazole can cause side effects, although not everybody gets them.

The frequency of side effects is classified into:

Very common: affect 1 out of 1-10 patients
Common: affect 1 out of 10-100 patients
Uncommon: affect 1 out of 100-1.000 patients
Rare: affect 1 out of 1.000-10.000 patients
Very Rare: affect less than 1 in 10,000 patients
Incidence not known: Can not be established the true incidence from the available data

Gastrointestinal side effects:

Pain in the upper stomach, nausea, vomiting, diarrhea, inflammation of the oral mucosa, taste disturbances, loss of appetite and exceptionally there have been produced some cases of reversible inflammation of pancreas (pancreatitis)

Allergic side effects:

Rash, itching, fever, urticaria (itching and irritation on the skin) generally accompanied by swelling of the feet, hands, throat, lips and airways (angioedema), and exceptionally (1/10.000) serious allergic reactions like anaphylactic shock .

Nervous System side effects:

Loss of sensitivity in extremities, headache, seizures and vertigo. Very rare cases of neurological disorders, for example, confusion, incoordination of movement, speech disorder, abnormal gait, involuntary eye movements and tremors, which may disappear with cessation of treatment.

Mental disorders: Including confusion and hallucinations.

Transient visual disturbances As double vision (diplopia) and myopia.

Hematologic and lymphatic side effectso:

Have been reported very rarely (1/10.000) cases of agranulocytosis or neutropenia (decrease of white blood cells, granulocytes or neutrophils) and thrombocytopenia (reduced platelet count).

Hepatobiliary side effects:

Have been reported very rarely (1/10.000) Reversible alterations of liver tests and cholestatic hepatitis.

This listing does not includes all adverse reactions related to the use of oral metronidazole, both well established as those that are under consideration or confirmation. In case you feel worse, consult with the doctor who has prescribed the drug IMMEDIATELY.

If you notice any side effects not listed in this website or in the leaflet accompanying the container, ask your doctor or pharmacist.

If any of the side effects gets serious, tell your doctor or pharmacist.

Date page update: October 19, 2010.


This page provides information to clarify some basic questions about this active principle. It is not exhaustive and, therefore, does not expose all of the available information and does not replace the information that can provide your doctor.

Like most drugs, this medication has risks and benefits. Your doctor has evaluated before prescribing, both ends. Any additional questions regarding this or any other medications, you should consult with your doctor.