Metronidazole, (often supplied under the brand name Flagyl) is an antibiotic used to treat a wide variety of bacterial and parasitic infections. It is used to treat infection of the skin and mouth, the respiratory system, the gastrointestinal tract and much of the reproductive system. Metronidazole is commonly prescribed to treat bacterial vaginosis (BV) in women.
Metronidazole works by preventing certain bacteria from reproducing and spreading, giving your body’s immune system the chance to get rid of the infection. For treatment of BV, this allows the natural balance of bacteria in the vagina to be restored.
Metronidazole should begin to make you feel better within a few days. However, you must finish the full course of tablets even if you are feeling better.
One tablet, three time per day for 5-7 days
|Type of Medicine||
Inhibits nucleic acid synthesis, disrupting DNA synthesis in bacteria, which prevents essential cell functions and replication
From £1.40 per tablet
Can include mental confusion, hallucinations, convulsions, headache, skin rash, darkening of the urine, muscle or joint pain
The active ingredient of each metronidazole tablet is 400 milligrams (mg) metronidazole.
The inactive ingredients are povidone, magnesium stearate, colloidal anhydrous silica and maize starch.
Please note: different brands of generic metronidazole may contain different ingredients than those listed here.
Metronidazole is not known to cause severe allergic reactions in people unless you have a hypersensitivity to this medication. However, as it does contain lactose as one of its inactive ingredients, if you have a severe lactose intolerance you might experience some uncomfortable gastrointestinal symptoms. It is otherwise present in small safe amounts and should not affect you if you have mild lactose intolerance.
Always take metronidazole as instructed by a doctor or pharmacist as the dose may differ depending on what type of infection you have. For treatment of bacterial infections in adults, a typical dose is 400mg three times per day (every 8 hours) for 5–7 days. For treatment of bacterial vaginosis, the dose is usually 400mg twice per day for 5–7 days; or alternatively a single dose of 2g. Your prescriber will inform you of the correct dose and duration of treatment.
Swallow the tablets whole with a glass of water, preferably during or just after a meal to avoid side effects such as nausea or vomiting. Do not crush or chew the tablets. If you forget to take a dose, try and take it as soon as you remember. However, if it is nearly time for your next dose, just skip the forgotten dose and take the next one as planned. Never take a double dose to make up for a missed one.
Metronidazole tablets should not be crushed or split.
Like all medications, metronidazole can cause side effects in some patients. If you experience any of the following rare side effects, stop taking Metronidazole and seek medical attention immediately:
Speak to your doctor if you experience any of the following side effects:
The following side effects affect less than 1 in 10,000 people, but should be reported immediately to a doctor or pharmacist:
The frequency of the following side effects cannot be estimated from the available data, these should be reported to your doctor also:
One of the most common side effects is nausea. If you experience this then it’s helpful to have small, simple meals and avoid overly spicy or rich foods. Drink plenty of water, particularly if you have vomiting. If the nausea is troublesome or if vomiting is preventing you from taking the tablets, consult your doctor as there may be a more suitable alternative treatment.
Do NOT take metronidazole tablets if you are allergic to any of the ingredients in this medication, or to other nitroimidazoles e.g. tinidazole.
Take particular caution and tell your doctor or pharmacist if:
Before taking metronidazole, tell your doctor or pharmacist if you are taking any other medications, including those purchased over the counter without a prescription. In particular, tell your doctor or pharmacist if you are taking any of the following:
Metronidazole should not be taken during pregnancy or breastfeeding unless absolutely necessary. You should inform your doctor if you are pregnant, think you might be pregnant or plan to become pregnant before taking this medication.
Do not drink alcohol while taking metronidazole or for the 48 hours after finishing your course. Combining alcohol with this medication can cause unpleasant side effects such as nausea, vomiting, stomach pain, hot flushes, heart palpitations and headaches.
For the treatment of infections such as bacterial vaginosis, there is little difference in effectiveness between metronidazole tablets and gel, and both work effectively to eradicate BV. The gel tends to be more expensive than the tablets and carries a slightly higher chance of causing vaginal thrush as a side effect. The tablets are more likely to induce gastrointestinal side effects such as nausea or vomiting, although these can be avoided by taking each dose with food. Each patient reacts differently to different forms of antibiotic, so if you are worried about any side effects, speak to your doctor for advice.
Metronidazole is an antibiotic, so it is vital that you complete the full course of treatment prescribed to you by your doctor. The length of the course will depend on the type of infection being treated, and even if your symptoms have gone, you must continue until the end of the course.
Metronidazole itself does not affect any type of oral contraception or prevent it from working. However, if you experience vomiting or severe diarrhoea as a side effect of metronidazole, your contraceptive pill may not prevent pregnancy. See the packet instructions of your contraception for advice if this happens.
Metronidazole is an antibiotic that is used to treat a wide variety of bacterial and parasitic infections.
Metronidazole can cause thrush in some patients if the antibiotics attack the normal, harmless bacteria which live in the vagina. This is more common in patients who use metronidazole gel rather than tablets.
Metronidazole does not affect fertility in men or women, but you should seek advice from your doctor if you are trying to get pregnant while using this medication.
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