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Terms Of Use


Brand Name(s) : Flagyl, Metrolyl, Metrogel, Metrotop, Norzol, Rosiced, Rozex, Zidoval, Zyomet
Side Effects


Metronidazole should be used with caution in:

  • the elderly, liver disease, kidney dialysis, patients with epilepsy (fitting), alcoholism, patients who have a disease of the nervous system (brain or spinal column), blood problems, the rare genetic condition acute porphyria. Metronidazole may darken the urine. Your doctor may with to carry out some blood tests if you need to use metronidazole for more than 10 days.

It should not be used in:

  • patients who are allergic to metronidazole, nitroimidazoles or to any of the ingredients in the medicine.

Also see list of precautions and interactions


Store below 25ºC and protect from light. Metronidazole suppositories should be stored below 20ºC


Metronidazole is used to treat or prevent infections caused by bacteria and parasites..

It is an antimicrobial drug, sometimes known as an antibiotic.

It is used to kill bacteria and parasites that can infect your body.

In general this drug is used to treat infections of the blood, brain, lungs, bone, genital tract (the part of the body involved in reproduction), pelvic area, stomach and intestines, gum infections and other dental infections, infected leg ulcers and pressure sores. Metronidazole is also used to prevent infection after surgery.

Benefits of being on this drug can include relief of symptoms associated with specific infections and prevention of infection.

Listed below are the typical uses of metronidazole.

  • Trichomoniasis (a sexually transmitted disease or STD)
  • Rosacea (a skin infection causing redness and spots on the face)
  • Vaginosis (infection and inflammation of the female genital area)
  • Amoebiasis (an infection of the intestine or liver)
  • Giardiasis (an infection of the intestine)
  • Gingivitis (swollen gums and ulcers in the mouth)
  • Other dental infections
  • Leg ulcers and pressure sores
  • Septicaemia and bacteraemia (blood infections)
  • Infection in the brain
  • Lung infection (pneumonia)
  • Bone infections (osteomyelitis)
  • Infection after childbirth
  • Abscess of the pelvis
  • Inflammation around the stomach and intestines
  • Infection after surgery
  • Cancer, to reduce the extremely unpleasant smell that is sometimes associated with fungating tumours

On occasion your doctor may prescribe this medicine to treat a condition not on the above list. Such conditions are listed below.

  • In combination with other antibiotics to treat bacterial infection in the stomach caused by Helicobacter pylori
  • Tetanus
  • Serious infection of the bowel/colon (antibiotic-associated colitis)


How often do I take it?

  • Metronidazole is available as tablets and a suspension for oral administration, and as an intravenous infusion, suppositories, gel and cream. The dose and how often you take your medicine will depend on the infection being treated and the type of metronidazole preparation you have been prescribed.
  • Tablets or capsules: Take this medication orally usually two or three times a day, swallowed whole not chewed, with plenty of water, with or after food. Metronidazole suspension should be taken orally an hour before food or on an empty stomach.
  • Suppositories: Insert one suppository into the rectum (back passage) usually two or three times a day.
  • Intravenous infusion: If you are unable to take metronidazole orally you may be prescribed metronidazole for administration through a drip into a vein. This is usually given by a doctor or nurse.
  • Topical gel or cream preparations: Apply to the affected area of the skin usually twice daily. The affected area should be clean and dry before applying metronidazole gel or cream.
  • Make sure you know exactly how often and how to take the metronidazole preparation that you have been prescribed. If you are unsure consult your doctor or pharmacist.

Use this medication for the duration of the prescription in order to get the most benefit from it.

Remember to use it at the same time each day - unless specifically told otherwise by your doctor.

Information on the time to maximum effect is not available.

Certain medical conditions may require different dosage instructions as directed by your doctor.

What dose?

  • Dosage is based on your age, gender, medical condition, response to therapy, and use of certain interacting medicines.

Do I need to avoid anything?

  • Metronidazole may make you feel sleepy, dizzy, confused, make you see or hear things that are not there (hallucinations), cause fitting (convulsions) and temporary problems with your eyesight such as blurred or double vision. If you develop any of these symptoms do not drive or operate machinery. Keep out of strong sunlight or UV light when using metronidazole gel or cream. Avoid using metronidazole skin gel or cream too close to the eyes as it may make your eyes water. If this happens or you accidentally get some of the gel or cream in your eyes, bathe them immediately with an eye wash or clean water. Consult your doctor or pharmacist for more details.

When can I stop?

  • Always complete the full course as prescribed by your doctor.


  • Skin irritation, burning and dryness (reported with skin preparations)
  • Watering of the eyes (reported with the application of skin preparations too close to the eye)
  • Fitting (convulsions)
  • Feeling confused and seeing or hearing things that are not there
  • Problems with your eyesight such as blurred or double vision
  • Skin rash
  • Headache
  • Dark urine (water)
  • Feeling sleepy or dizzy
  • Painful muscles of joints
  • Numbness, tingling, pain or a feeling of weakness in the arms and legs
  • Unpleasant taste in the mouth
  • Furred tongue
  • Feeling sick and being sick
  • Stomach upset or diarrhoea
  • Loss of appetite
  • Worsening of the skin infection rosacea
  • Liver problems
  • Inflammation of the pancreas (pancreatitis)
If any of these persist or you consider them severe then inform your doctor or pharmacist. Further information on side effects can be found in the patient information leaflet.

Tell your doctor immediately if you develop any of the following symptoms:

  • Swelling of the hands, feet, ankle, face, lips or throat which may cause difficulty swallowing or breathing and an itchy, lumpy rash or nettle rash (these symptoms may be caused by an allergic reaction to metronidazole. You should stop taking metronidazole immediately if these symptoms occur.
  • Fever, stiff neck, headache, seeing or hearing things that aren't there, being more sensitive to light than usual, problems using your arms or legs and problems speaking or feeling confused. These symptoms may be caused by a very rare and serious brain condition called encephalopathy. You should stop taking metronidazole immediately if these symptoms occur.
  • Skin and whites of the eyes turning yellow in colour (this may be a sign of the liver problem jaundice).
  • Unexpected infections, mouth ulcers, bruising, bleeding gums or feeling very tired.
  • Very severe pains in your stomach which may reach through to your back.

Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

A serious allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of a serious allergic reaction include: rash, itching/swelling (especially of the face/tongue/throat), dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.


Before taking metronidazole, tell your doctor or pharmacist if you are allergic to it; or to other antibiotics; or if you have any other allergies.

This medication should not be used if you have certain medical conditions. Before using this medicine, consult your doctor or pharmacist if you have: an allergy to metronidazole or to any of the other ingredients in the medicine, or are pregnant or breastfeeding.

Before using this medication, tell your doctor or pharmacist your medical history, especially any of the following: liver disease, kidney dialysis, epilepsy (fitting), alcoholism, disease of the brain or spinal column, blood problems, the rare genetic condition acute porphyria.

Before having surgery, tell your doctor or dentist that you are taking this medication.

Does alcohol intake affect this drug?

  • You must not drink alcohol whilst taking metronidazole and for 48 hours after finishing your medicine. Drinking alcohol while taking metronidazole can cause unpleasant side effects including feeling sick and being sick, stomach pains, hot flushes, fast or irregular heartbeat (palpitations) and headache.

The elderly: metronidazole should be used with caution in the elderly particularly at high doses.

Pregnancy and breastfeeding - please ensure you read the detailed information below


It is not recommended to take metronidazole if you are pregnant or planning to become, pregnant.

It is sensible to limit use of medication during pregnancy whenever possible. However, your doctor may decide that the benefits outweigh the risks in individual circumstances and after a careful assessment of your specific health situation.

If you have any doubts or concerns you are advised to discuss the medicine with your doctor or pharmacist.


It is not recommended to take metronidazole if you are breastfeeding.

It is sensible to limit use of medication during breastfeeding whenever possible. However, your doctor may decide that the benefits outweigh the risks in individual circumstances and after a careful assessment of your specific health situation.

If you have any doubts or concerns you are advised to discuss the medicine with your doctor or pharmacist.


Your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with them first.

This drug should not be used with alcohol because very serious, possibly fatal interactions may occur.

If you are currently using any of these medications, tell your doctor or pharmacist before starting metronidazole:

Before using this medication, tell your doctor or pharmacist of all prescription and non-prescription/herbal products you may use, especially of:

  • Medicines to thin the blood such as warfarin
  • Medicines for epilepsy or fitting (such as phenytoin, primidone)
  • Barbiturates such as phenobarbital for epilepsy (fitting)
  • Medicines for cancer (such as 5-fluorouracil, busulfan)
  • Mycophenolate (to prevent organ rejection after transplant)
  • Disulfiram (used in alcohol dependence)
  • Lithium (used to treat depression)
  • Medicines containing oestrogen (including the oral contraceptive pill)
  • Ciclosporin (to prevent organ rejection after transplant)
  • Medicines for stomach ulcers (such as cimetidine)
  • Oral typhoid vaccine

This information does not contain all possible interactions. Therefore, before using metronidazole, tell your doctor or pharmacist of all the products you use.


If you take more metronidazole than you should, or accidentally swallow metronidazole gel, cream or suppositories, tell your doctor or got to your nearest hospital casualty department straightaway. Take any remaining medicine with you so that the doctor knows what you have taken.

If you think you, or someone you care for, might have accidentally taken more than the recommended dose of metronidazole or intentional overdose is suspected, contact your local hospital, GP or if in England call 111. In Scotland call NHS 24. In Wales, call NHS Direct Wales. In the case of medical emergencies, always dial 999.


If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule. Do not double the dose to catch up.

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Source: Selected from data included with permission and copyrighted by Boots UK Limited. This copyrighted material is sourced from a licensed data provider and is not for distribution, except as may be authorised by the applicable terms of use.
CONDITIONS OF USE: The information in this database is intended to supplement, not substitute for, the expertise and judgement of healthcare professionals. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse events, nor should it be construed to indicate that use of a particular medicine is safe, appropriate or effective for you or anyone else. A healthcare professional should be consulted before taking any medicine, changing any diet, or discontinuing any course of treatment.

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