Metronidazole
In brief
- Metronidazole is a prescription-only medicine (POM) in the UK.
- Metronidazole is used to treat anaerobic bacterial infections, bacterial vaginosis, trichomoniasis, amoebiasis, giardiasis, dental infections, and some rosacea cases. It works by damaging the DNA of susceptible microorganisms, which stops them from growing and kills them.
- The usual adult dose depends on the condition: 500 mg every 8 hours for anaerobic infections, 2 g once or 250 mg three times daily for trichomoniasis, 500 mg twice daily for bacterial vaginosis, and 500–750 mg three times daily for amoebiasis or giardiasis.
- Metronidazole is available as tablets, oral suspension, intravenous infusion, topical cream or gel, and vaginal gel.
- It usually starts working within a few hours, although symptom improvement may take 1–2 days, depending on the infection and the form used.
- The duration of action is typically around 8 hours for standard oral dosing, so it is often taken multiple times a day. Treatment courses commonly last from 3 to 14 days depending on the indication.
- Do not drink alcohol during treatment and for at least 48 hours after the last dose, as metronidazole can cause a disulfiram-like reaction with flushing, nausea, vomiting, and abdominal cramps.
- The most common side effects are nausea, a metallic taste, vomiting, diarrhoea, headache, dizziness, and darkened urine.
- Would you like to try metronidazole without a prescription?
Basic metronidazole information
- INN (international nonproprietary name): Metronidazole.
- Brand names available in the United Kingdom: Flagyl; generic metronidazole.
- ATC code: J01XD01.
- Forms and dosages: Tablets 200mg, 400mg, 500mg; oral suspension 200mg/5ml; IV infusion 500mg/100ml (5mg/ml); topical cream and gel 0.75%; vaginal gel 0.75%.
- Manufacturers in the United Kingdom: Several generic suppliers.
- Registration status in the United Kingdom: Authorised by the MHRA; prescription-only medicine (POM).
- OTC / Rx classification: Prescription-only medicine (POM).
Metronidazole at a glance
In UK pharmacies, metronidazole tablets, gels, creams and vaginal preparations are commonly supplied for bacterial vaginosis, trichomoniasis, anaerobic infections, dental infections, amoebiasis, giardiasis and rosacea.
The medicine’s INN is Metronidazole, its ATC code is J01XD01, and a well-known brand is Flagyl.
- What it is
- An antibacterial and antiprotozoal medicine used for several common infections and local treatment needs.
- How UK patients get it
- Usually through an NHS prescription or a private prescription.
Common reasons for use
Common reasons include bacterial vaginosis (BV) after discharge or odour, trichomoniasis after a sexual health consultation, a painful dental abscess, and rosacea when the face is red and inflamed.
Oral metronidazole is also used for travel-related gut infections such as giardiasis and amoebiasis, while metronidazole gel and cream are used for local treatment rather than tablets.
Legal status and availability in the UK
Metronidazole is a prescription-only medicine (POM) in the UK.
In our online pharmacy, metronidazole is available without a prescription, with discreet delivery to the United Kingdom in 9–21 days.
Available forms and strengths
Metronidazole comes in several forms, and the right one depends on the condition being treated.
The most familiar options are oral tablets, topical gel or cream, and vaginal gel for BV.
Suspension and IV injections are also important formulations, although they are used less often outside hospital.
| Form | Strengths / presentation | Typical use |
|---|---|---|
| Tablets | 200mg, 400mg, 500mg | Systemic infections, BV, trichomoniasis, giardiasis, amoebiasis |
| Oral suspension | 200mg/5ml | Children |
| IV infusion | 500mg/100ml | Hospital and critical care use |
| Topical cream or gel | 0.75% | Rosacea and local skin use |
| Vaginal gel | 0.75% | Bacterial vaginosis and related vaginal infections |
Which form is used for which need
Oral tablets are used when a systemic effect is needed, such as for anaerobic infection or a bowel infection.
Gel or cream suits local treatment, especially rosacea or a skin flare-up where a tablet is not necessary.
Vaginal gel is a form used for BV treatment, especially when direct local therapy is wanted.
What metronidazole is prescribed for
The medicine is commonly prescribed for practical, everyday scenarios rather than rare specialist cases.
- Bacterial vaginosis, where discharge and odour are the main concerns.
- Trichomoniasis, where oral tablets are usually used.
- Anaerobic infections, including abdominal and deep tissue infections.
- Dental abscesses, when a dentist wants anaerobic cover.
- Amoebiasis, often linked with travel or contaminated food and water.
- Giardiasis, with diarrhoea, bloating and stomach upset.
- Rosacea, where topical therapy is often chosen.
Combination products
Metronidazole also appears in combination packs, including products with diloxanide furoate in some brands.
It is also used in some H. pylori regimens as part of combination treatment plans.
How to take it: dosing patterns by condition
Correct dosing depends on the indication, the formulation and the patient’s clinical situation.
That is why a pharmacy check is important before anyone starts a course on their own.
| Condition | Typical adult dose | Usual duration | Practical point |
|---|---|---|---|
| Anaerobic infections | 500mg IV or oral every 8 hours | 7 to 10 days | Complete the course even if the pain starts easing |
| Trichomoniasis | 2g once or 250mg three times daily | 1 to 7 days | Partners may also need treatment depending on the diagnosis |
| Bacterial vaginosis | 500mg twice daily or 0.75% topical | 5 to 7 days | Local therapy may suit some patients better than tablets |
| Amoebiasis or giardiasis | 500mg to 750mg three times daily | 5 to 10 days | Travel-related infection often needs a full course |
| Rosacea | Apply cream or gel twice daily | Several weeks | Improvement is usually gradual rather than instant |
Practical dosing points
Metronidazole dosage should be followed exactly as prescribed.
It is best to finish the course even if symptoms improve early, because stopping too soon can mean the infection returns.
Missed dose basics
If a dose is missed and the next one is not due soon, take it when remembered.
If the next dose is nearly due, skip the missed dose and return to the normal schedule.
Do not double up.
Special populations: children, older adults, pregnancy, liver and kidney issues
Some people need extra caution because the standard adult dose is not always the safest option.
That is especially true in children, pregnancy, significant liver disease and dialysis patients.
- Children
- Usually dosed by weight at 7.5mg/kg by mouth every 8 hours, with a maximum usually of 500mg per dose.
- Older adults
- Standard adult doses are usually used, but monitoring is closer because CNS effects and cumulative toxicity can be more of a concern.
- Severe liver impairment
- The dose is usually reduced by 50%.
- Renal failure and dialysis
- Adjustment is usually not needed unless the impairment is severe, but dialysis patients may need careful review and possible post-dialysis supplementation.
- Pregnancy
- First-trimester use is restricted for some indications, and later pregnancy use should be based on benefit versus risk.
When extra care is needed
Extra care is needed particularly when a patient is pregnant, elderly, on dialysis, or describing a history of epilepsy or liver disease.
Common side effects
Most people notice side effects early, and the good news is that many are mild and temporary.
- Nausea, often mild and usually manageable.
- Metallic taste, which can be unpleasant but is commonly expected.
- Vomiting or diarrhoea, especially if the stomach is already sensitive.
- Headache and dizziness.
- Darkened urine, which is usually benign and reversible.
- Skin rash and itching.
- Oral or vaginal candidiasis with prolonged use.
What’s usually expected
A metallic taste, mild stomach upset and a temporary change in urine colour are among the better-known metronidazole side effects.
These do not always mean the medicine must be stopped, but they do deserve attention if they become bothersome.
When to seek help
Severe rash, persistent vomiting, neurological symptoms, or a suspected allergy should trigger prompt medical advice.
If symptoms feel worse rather than better, the prescription should be reviewed.
Safety warnings, interactions, and who should avoid it
Safety checks are not optional with metronidazole because the medicine is prescription only and the interaction list matters.
Alcohol avoidance is especially important because metronidazole can cause a disulfiram-like reaction when combined with ethanol.
| Status | Examples | Pharmacy advice |
|---|---|---|
| Avoid | Allergy to metronidazole or other nitroimidazoles; history of hypersensitivity | Do not use without specialist review |
| Use with caution | Epilepsy or other CNS disorders; severe hepatic impairment; chronic alcoholism; pregnancy beyond first trimester; children | Check dose and suitability carefully |
| Ask a pharmacist | Warfarin or other anticoagulants, lithium, and other prescription medicines | Interactions may be clinically important |
Checks before starting
Before starting, the usual checks include allergies, liver disease, seizure history, alcohol use and current medicines.
People often forget to mention anticoagulants, lithium or other regular prescriptions, so that question matters.
Interactions
Anyone taking warfarin, other anticoagulants or lithium should tell the pharmacist or prescriber before starting metronidazole.
The same applies if there are concerns about epilepsy, liver disease or heavy alcohol use.
What improvement should feel like
Most people judge treatment success by how symptoms change over a few days.
With metronidazole, that usually means less discharge, less odour, less pain, calmer gut symptoms, or a rosacea flare that starts to settle.
Day 1–2: The medicine has started, but symptoms may still be obvious.
Day 3–5: Many patients notice a clear shift, such as reduced odour, less discharge or easing stomach symptoms.
End of course: Treatment should be finished even if the infection seems to have settled.
When a patient may need review
Worsening symptoms, fever, no improvement, repeated infection or intolerance are all reasons to seek a review.
Some people also need reassessment if recurrent BV keeps coming back after treatment.
Brand names and manufacturers
Many UK patients receive a licensed generic rather than a named brand.
- Flagyl remains the best-known brand name in the UK.
- Rozex is a topical product name patients may recognise.
- Major suppliers include Pfizer, Teva, Zydus Lifesciences, Galderma, Aurobindo and Hikma.
Regulatory status in the UK
Metronidazole is authorised by the MHRA and is a prescription-only medicine (POM) in the UK.
Pharmacist checks, a prescription requirement and safe supply are standard, and there is no over-the-counter route for routine access.
Storage
Most people store metronidazole at home until the course is finished, so sensible storage matters.
- Store tablets, capsules and cream at 15–25°C.
- Protect the medicine from heat, freezing and moisture.
- Keep IV vials protected from light.
- Keep oral and topical forms in their original packaging.
- Store out of children’s reach.
- Check the expiry date before travel or reuse.
Good storage habits
Bathroom cupboards are not ideal because humidity can shorten stability.
When travelling, the original box and leaflet are worth keeping.
Missed dose, overdose, and when to seek advice
- Missed dose
- Take it when remembered unless the next dose is nearly due. Do not double up.
- Overdose
- May cause nausea, ataxia, seizures and peripheral neuropathy, and supportive treatment is recommended.
- When to contact a pharmacist
- If there is an overdose, neurological symptoms, a suspected serious reaction, or uncertainty about interactions.
Doubling a dose
Doubling a dose does not make the medicine work better.
It only increases the chance of side effects and should be avoided.
Delivery across the United Kingdom
| City | Region | Delivery time |
|---|---|---|
| London | Greater London | 9–21 days |
| Birmingham | West Midlands | 9–21 days |
| Manchester | North West England | 9–21 days |
| Glasgow | Scotland | 9–21 days |
| Edinburgh | Scotland | 9–21 days |
| Cardiff | Wales | 9–21 days |
| Belfast | Northern Ireland | 9–21 days |
| Liverpool | North West England | 9–21 days |
| Leeds | West Yorkshire | 9–21 days |
| Bristol | South West England | 9–21 days |
| Newcastle upon Tyne | North East England | 9–21 days |
| Nottingham | East Midlands | 9–21 days |
| Sheffield | South Yorkshire | 9–21 days |
| Southampton | South East England | 9–21 days |
| Aberdeen | Scotland | 9–21 days |
