Metronidazole 400mg Tablets

• Metronidazole 400mg is an antibiotic that stops the growth of bacteria or parasites that cause infection. 

• How to take Metronidazole 400mg: Swallow the tablet whole with a full glass of water, preferably with or after food, to minimise stomach upset.

• Dosage: Metronidazole prescriptions are usually prescribed in two regimens: For-bv: 400mg twice a day for 7 days. Please ensure you consult your doctor on which Metronidazole dosage is correct for you.

• Common side effects: Nausea, metallic taste, headache, dizziness, stomach upset.

• Precautions: Avoid if you have liver or nerve problems. Please consult the NHS and your doctor before consumption. 

• Alcohol warning: No alcohol during treatment or for 48-72 hours after completion of dosage. 

• It is not used for yeast infections or infections caused by aerobic bacteria.

Metronidazole tablets are a generic antibiotic and antiprotozoal medicine that is highly effective in treating bacterial vaginosis (BV). 

It works by killing the anaerobic bacteria that cause the infection, helping to restore the natural balance of bacteria in the vagina by clearing the infection.

It’s available under several brand names, including:

• Flagyl® (oral/tablet form)
• Metrogel®, Metrolotion®, Noritate® (mostly for skin or vaginal use)

Metronidazole is usually taken as a tablet (400 mg or 500 mg) or used as a vaginal gel, depending on what your clinician prescribes.

While Metronidazole tablet treats BV very effectively, it does not work for yeast infections or infections caused by aerobic bacteria, only for certain types of bacteria like those causing BV.

However, Ashcroft Pharmacy offers Metronidazole only in tablet form, which is the first-line treatment for vaginal infection BV.

Metronidazole 400mg is an antibiotic and antiprotozoal that targets anaerobic bacteria, which don’t need oxygen to survive. It prevents the growth of these bacteria, therefore preventing infection.

As the harmful bacteria are cleared, natural Lactobacilli bacteria (good bacteria) return, helping restore a healthy balance in the vagina.

After starting the treatment, you should feel better within a few days if taken as suggested.

If you're diagnosed with bacterial vaginosis (BV), most doctors in the UK will prescribe metronidazole tablets in one of two common ways:

1. Single high dose – You take five 400mg tablets (2g total) all at once.

• This is a quick treatment, but some people may get more side effects like nausea or headache.

2. 7-day course – You take one 400mg tablet twice a day (morning and evening) for 5-7 days.

• This is the option most commonly used, especially if you’ve had BV in the past or tend to get it repeatedly.

Both are effective, but the 5-7 day course is more commonly recommended, especially if you’ve had BV before or get it regularly. The single dose may cause more side effects at first.

Most people start feeling better within 2 to 3 days of taking metronidazole tablets. If your BV symptoms persist after completing the treatment, contact your doctor.

They will also tell you:

• Don’t drink alcohol during treatment and for 2 days after, as it can make you feel very unwell. It is generally advised to wait 24 to 72 hours for the drug to clear from your system and prevent interactions. Waiting 48 hours is usually sufficient, but 72 hours may be recommended for extra caution.
• Take tablets after food to avoid stomach upset.
• Finish the course, even if your symptoms go away before it’s done.

If symptoms don't go away or come back soon after, your doctor may suggest a different treatment, such as vaginal gel or another antibiotic.

Who should not take metronidazole 400mg tablets?

You should always consult a doctor if you are under any other medication or suffering from other illnesses. The following are groups of people who should consult a doctor before taking Metronidazole.

• If you are having liver problems.
• If you have a dialysis appointment.
• If you are unable to stop taking alcohol.
• If you have a history of allergic reactions caused by metronidazole.

Warning and precautions

Always follow doctors' advice while taking Metronidazole. Avoid taking alcohol when under Metronidazole treatment. You should also not take alcohol 2 days after completing your dosage.

• Visit a doctor if you are still experiencing bacterial vaginosis symptoms even after taking Metronidazole.
• Avoid taking Metronidazole if you have neurological conditions, as it can worsen these conditions and consult your doctor/ pharmacist.

Metronidazole can sometimes cause dizziness, and alcohol may worsen this effect. Avoid driving or operating machinery if you feel dizzy after taking this medicine. If your work requires full concentration, ensure you are well-rested before continuing with such tasks.

Do not take metronidazole 400mg if you are about to receive certain vaccines, as this medicine may reduce their effectiveness. Always inform your doctor or pharmacist about any upcoming immunisations.”

For more details, please read the patient leaflet before taking Metronidazole.

Metronidazole 400mg tablets can cause different reactions in different patients. Some patients may prefer taking other forms of medication to treat bacterial vaginosis. Examples of alternative treatments that can be used in place of metronidazole include:

Zidoval vaginal gel (Metronidazole 0.75% vaginal gel):

Zidoval vaginal gel treatment contains metronidazole. This treatment is taken by inserting it into the vagina for 5 consecutive days before going to bed.

Dalacin cream.(Clindamycin 2% vaginal cream)

You can treat bacterial vaginosis by inserting Dalacin cream into the vagina using an applicator. Dalacin cream works effectively when taken as a 7-day course.

Clindamycin tablets

Clindamycin tablets are recommended for pregnant women. It is available as a 300mg tablet and should be taken 2 times a day for 7 days.

Other medications and Metronidazole.

You should inform your doctor if you are under any other treatment before taking Metronidazole 400mg tablets. Speak to your doctor before taking Metronidazole if you are taking the following medicines.

• Busulfan is a type of medicine used to treat leukemia
• Treatments used to treat epilepsy
• Lithium
• Fluorouracil
• Ciclosporin
• Phenobarbital

Research shows that bacterial vaginosis can complicate your pregnancy. There is no proven evidence that metronidazole can cause preterm delivery, low birth weight, stillbirth, or birth defects.

• While pregnant you should not take a single high dose of metronidazole.
• Pregnant mothers should seek medical advice before taking Metronidazole

Metronidazole tablets should not be taken during the first 3 months of pregnancy and are not recommended for use during the rest of the pregnancy.

If you're breastfeeding, pause while taking Metronidazole tablets and wait 12-24 hours after finishing the course before breastfeeding again.

Ensure you inform your doctor that you are Breastfeeding to receive the right instructions for the medication.

You can reduce the risk of getting bacterial vaginosis by observing the following lifestyle habits.

• Avoid smoking
• Avoid using vaginal deodorants
• Always take a shower instead of a bath
• Avoid using strong detergent when washing your underwear
• Avoid using shower gel, bubble baths, perfumed soap, and antiseptic in the bath
• To wash your genital area use water and plain soap. Avoid using creams to wash your genital area.

Metronidazole 400mg Patient leaflet (accessed 11 May 2025) 

Healthcare Professionals (SmPC) (accessed 11 May 2025) 

https://www.ncbi.nlm.nih.gov/books/NBK582844/ (accessed 11 May 2025) 

https://www.nhs.uk/medicines/metronidazole/pregnancy-breastfeeding-and-fertility-while-taking-or-using-metronidazole/ (accessed 11 May 2025) 

https://www.nhs.uk/conditions/bacterial-vaginosis/ (Last accessed 11 May 2025) 

Dalacin Cream 2% - Patient Information Leaflet (PIL) (Last accessed 11 May 2025)