Metronidazole for bacterial infection
Flagyl
Granskad av Dr Colin Tidy, MRCGPSenast uppdaterad av Michael Stewart, MRPharmSLast updated 26 Mar 2023
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Swallow metronidazole tablets with plenty of water. Take them with a meal or a snack.
Do not drink alcohol while you are taking metronidazole, and for 48 hours after finishing your course of treatment.
Space your doses evenly throughout the day, and keep taking the medicine until the course is finished.
The most common side effects of metronidazone are feeling sick (nausea) and being sick (vomiting).
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About metronidazole
Typ av medicin | Antimicrobial agent (antibiotic) |
Används för | To treat or prevent infection |
Även kallad | Flagyl® |
Tillgänglig som | Tablets, oral liquid medicine, suppositories, and injection |
What is metronidazole used for?
Tillbaka till innehållMetronidazole is an antibiotic used to treat a wide variety of bacterial infections caused by anaerobic bacteria and types of micro-organisms called protozoa.
These types of organisms often cause infections in areas of the body such as the gums, pelvic cavity and tummy (stomach or intestines) because they do not need oxygen to grow and multiply.
Metronidazole is commonly prescribed to treat bacterial vaginosis, and, is also prescribed before gynaecological surgery and surgery on the intestines, to prevent infection from developing.
Metronidazole is also used, alongside other medicines, to get rid of Helicobacter pylori, a bacterial infection often associated with stomach ulcers.
It can safely be taken by people who are allergic to penicillin.
Metronidazole is available as a skin preparation also. This leaflet does not give information about metronidazole when it is used for skin conditions, but there is more information available in a separate leaflet called Metronidazole skin gel and cream.
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Side effects of Metronidazole
Tillbaka till innehållCommon side effects of metronidazole are:
Illamående.
Being sick.
Changes in how things taste.
Furred tongue
Sore mouth.
Lack of appetite.
You will find a full list in the manufacturer's information leaflet supplied with your medicine.
The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.
How to manage metronidazole side effects
Tillbaka till innehållMetronidazole side effects | Vad kan jag göra om jag upplever detta? |
Feeling sick or being sick | Stick to simple foods. Make sure you take your doses after a meal or a snack |
Changes in the way things taste, furred tongue, sore mouth | Ask your pharmacist to recommend a suitable mouthwash |
Lack of appetite | This should soon pass, but in the meantime choose food that you usually enjoy |
Om du upplever några andra symtom som du tror kan bero på denna medicin, tala med din läkare eller apotekare.
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Who should not take metronidazole
Tillbaka till innehållSome medicines aren’t suitable for certain health conditions or may require extra care. Before taking metronidazole, it is important to let your doctor know:
Om du är gravid eller ammar.
If you feel you will be unable to stop drinking alcohol for the duration of your treatment.
If you have any problems with the way your liver works.
If you have a rare inherited blood disorder called porphyria.
Om du tar några andra läkemedel. Detta inkluderar alla läkemedel du tar som finns att köpa utan recept, samt växtbaserade och komplementära läkemedel.
Om du någonsin har haft en allergisk reaktion mot en medicin.
How to take metronidazole
Tillbaka till innehållRead the information leaflet in your pack before starting. It explains metronidazole and lists possible side effects.
Take the tablets or liquid exactly as your doctor or dentist tells you. Your dose depends on the type and severity of your infection.
Adults often take 400 mg two or three times a day, but your dose may be different. Children’s doses depend on age and weight. You're doctor will tell you what dose to take.
Space your doses evenly throughout the day and finish the full course unless your doctor tells you to stop. Stopping early can make the infection come back.
Most courses of metronidazole last about seven days, but some can last anywhere from 3-14 days. For certain infections, you may be given one large dose, usually five 400 mg tablets (2 g),to take at once.
Take each of your doses with a snack or just after eating a meal. Swallow the tablets whole (that is, without chewing or crushing them) with a full glass of water.
If you forget to take a dose, take it as soon as you remember and try to space your remaining doses evenly throughout the rest of the day. Ta inte två doser samtidigt to make up for a forgotten dose.
If you have been given metronidazole suppositories
Remove the suppository from its wrapping.
Using your finger, gently push the suppository into your back passage (rectum) as far as is comfortable. Many people find that inserting a suppository is easier if they squat or bend forward.
Remain still for a few moments to help you to hold the suppository in place.
Wash your hands.
Få ut det mesta av din behandling
Tillbaka till innehållMetronidazole can make your urine look darker. This is usually harmless, but if you also get stomach pain, feel sick, or feel unwell, tell your doctor.
Check with a pharmacist before buying any other medicines. Some cold and cough products contain alcohol and shouldn’t be taken with metronidazole.
If you need to take metronidazole for more than 10 days, your doctor may arrange tests. Be sure to attend any appointments.
Viktigt: do not drink alcohol while you are on metronidazole and for 48 hours after finishing your course of treatment. This is because drinking alcohol with metronidazole is likely to make you feel very sick (nauseated) and cause other unpleasant effects, such as the sensation of having a 'thumping heart' (palpitations), hot flushes, and headache.
How to store metronidazole
Tillbaka till innehållFörvara alla läkemedel utom räckhåll och synhåll för barn.
Förvara på en sval, torr plats, borta från direkt värme och ljus.
Viktig information om alla läkemedel
Tillbaka till innehållViktig information om alla läkemedel
Ta aldrig mer än den föreskrivna dosen. Om du misstänker att du eller någon annan kan ha tagit en överdos av denna medicin, gå till akutmottagningen på ditt lokala sjukhus. Ta med behållaren, även om den är tom.
Om du ska genomgå en operation eller tandbehandling, informera den som utför behandlingen om vilka mediciner du tar.
Denna medicin är för dig. Ge den aldrig till andra människor även om deras tillstånd verkar vara detsamma som ditt.
Behåll aldrig föråldrade eller oönskade mediciner. Ta dem till ditt lokala apotek som kommer att ta hand om dem åt dig.
Om du har några frågor om denna medicin, fråga din apotekare.
Rapportera biverkningar av ett läkemedel eller vaccin
Om du upplever biverkningar kan du rapportera dem online via Yellow Card website.
Vanliga frågor
Tillbaka till innehållHow long does it take for metronidazole to work?
Metronidazole usually starts to work within 1-2 days, with most people noticing an improvement in their symptoms after 48 hours. Always finish your course of treatment even if you are feeling better.
Is it safe to take metronidazole during pregnancy?
Yes, it is usually safe to take metronidazole during pregnancy if it is prescribed to you. However, always let your doctor know that you are pregnant before taking metronidazole.
Can you drink alcohol when taking metronidazole?
No, you should not drink alcohol if you are taking metronidazole as it can cause a strong reaction, including nausea, vomiting, flushing, headaches, and a fast heartbeat. You should wait until 2 days after your last dose before having alcohol.
How long does metronidazole stay in your system for?
Metronidazole stays in your system for about 2-3 days after your last dose. It has a half-life of around 8 hours, which means it takes about 8 hours for the amount of the drug in your bloodstream to reduce by half.

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Vidare läsning och referenser
- Manufacturer's PIL, Flagyl® 200 mg and 400 mg Tablets; Sanofi, The electronic Medicines Compendium. Dated December 2021.
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Artikelhistorik
Informationen på denna sida är skriven och granskad av kvalificerade kliniker.
Next review due: 25 Sept 2027
26 Mar 2023 | Senaste versionen

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