Metronidazole 400mg Tablets

  • Used for bacterial infections, most commonly Bacterial Vaginosis (BV)
  • Kills excess bacteria and restores the balance of Vaginal Bacteria
  • Effective in clearing symptoms in just 48 hours

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What Metronidazole 400mg tablets?

Metronidazole is one of the most commonly prescribed medcines in the world, it is currently on the World Health Organisation's List of Essential Medicines.

Metronidazole is an antibiotic and antiprotozoal medication, often sold under the brand name Flagyl.

It is a prescription-only medicine (POM) that is commonly used for bacterial infections, such as bacterial vaginosis.

We sell Metronidazole 400 mg in packets of 14 tablets. It also comes available as a liquid, suppository, a vaginal gel, or external cream or gel.

What is Metronidazole 400mg used to treat?

Metronidazole 400mg is primarily used to treat bacterial infections, in particular bacterial vaginosis, which is a bacterial infection of the vagina. This condition affects many females during the course of their lifetime.

Metronidazole is also approved for the treatment of trichomoniasis. Trichomoniasis is a sexually transmitted infection that is caused by a tiny parasite called Trichomonas vaginalis (TV).

Whist bacterial vaginosis and trichomoniasis may seem and sound very similar, they are somewhat different. In summary, BV is caused by excessive vaginal bacteria, whilst trichomoniasis is caused be a little parasite.

Metronidazole can also treat infections all over the body, including the stomach, liver, skin, joints, brain and respiratory tract.

It is normally effective in clearing symptoms after just 48 hours. If you have been taking the medicine for longer than 10 days, your doctor may wish to review your progress to see if another medicine might be more suitable for you.

How do Metronidazole 400mg tablets work?

Bacterial vaginosis is believed to be caused by a change in the balance of bacteria that live in the vagina. This condition is characterised by unusual vaginal discharge that often has a fishy odour, especially after sex.

While it is not classed as a sexually transmitted infection (STI), women who are sexually active are more likely to suffer from bacterial vaginosis. Having this condition can also make it easier for you to contract an STI.

Metronidazole 400mg works to treat bacterial vaginosis by stopping the bacteria and parasites that cause the infection from growing. It has the same mechanism of action for other bacterial infections that occur elsewhere on the body, such as infected leg ulcers or oral infections.

Metronidazole Dose

Metronidazole tablets should be taken after you have eaten. Swallow them whole with a drink of water; do not crush or chew the tablets.

For most infections, your doctor will likely instruct you to take 1 tablet twice a day for 7 days. Some infections may only need a single dose, while others may require up to two weeks of treatment.

infection Dose
Bacterial Vaginosis 400-500mg twice daily for 5-7 days
Trichomoniasis 200mg 3 times daily for 7 days or 400-500mg twice daily

Who can take Metronidazole 400mg?

Metronidazole is safe for most adults and children to use, but it is not a suitable antibiotic for everyone.

To make sure this treatment is safe for you, you should check with your doctor before taking it if you have any of the following conditions:

  • You have or have ever had liver problems
  • You have had an allergic reaction to Metronidazole or any other medications in the past
  • You are currently pregnant or breastfeeding
  • You do not feel that you will be able to stop drinking alcohol while taking Metronidazole
  • You are having dialysis
  • You have a disease of the nervous system

If you wish to use the vaginal gel, you should also check with your doctor if you think you may have vaginal thrush.

Is it safe to take Metronidazole during pregnancy?

Studies have shown that taking Metronidazole during pregnancy for the treatment of trichomoniasis and bacterial vaginosis is safe and shows no teratogen risk.

Treating bacterial infections during pregnancy can be crucial to the health of a mother and baby. If left untreated, bacterial infections can increase the chance of a premature labour. 

The use of Metronidazole during pregnancy should be subject to a clinical risk assessment from your doctor who will weigh up how necessary the treatment is against any potential risks that may arise as a result of using the medicine whilst pregnant. 

Other considerations will be taken into account during the clinical risk assessment such as, if there are any underlying conditions as well as how many weeks pregnant you are.

Metronidazole Side Effects

Like all medicines, Metronidazole comes with a risk of certain side effects, although these will not affect everyone who uses it.

If you are using Metronidazole cream or gel, you are unlikely to experience any adverse effects.

However, when taking the tablets or liquid, side effects are more likely.

Do not drink alcohol while taking Metronidazole and for at least 48 hours after your treatment is complete. Alcohol can interact with Metronidazole, which can cause vomiting or nausea.

Common side effects of these tablets may include:

  • Nausea or vomiting
  • Diarrhoea
  • A metallic taste in your mouth or a furry tongue

Speak to your doctor if any of the above reactions bother you or do not go away.

This list is not exhaustive. Please, refer to the Side Effects tab on this page for a list of further reactions you may experience while using Metronidazole tablets.

Always read the information leaflet that will come with your medicine for a comprehensive list.

Alternative treatments for bacterial vaginosis

There are other medicines available to treat bacterial vaginosis if Metronidazole is not suitable for you to use.

Balance Activ is a vaginal gel that contains lactic acid, which works to restore your body’s natural pH balance. This 7-day treatment should be applied before going to sleep, allowing it to work overnight. Balance Activ gets to work straight away and you should have noticed a considerable improvement after just a few days. Balance Activ can be bought without needing a prescription.

You can also order Canestest, which is a self-test kit for vaginal infections including bacterial vaginosis. This test provides instant results and will help to make sure you receive the most appropriate treatment for your condition.

Metronidazole is also available as a Gel, a study into the efficacy of both the Gel and Oral versions of Metronidazole when treating Bacterial vaginosis found them to be as effective. However, patients reported fewer gastrointestinal side effects when using the gel.

Can you buy Metronidazole 400mg online?

Yes, you can buy Metronidazole 400mg tablets online from most UK online pharmacies. You will be required to complete an online health consultation which will allow a doctor to review your condition to ensure you are receiving the most suitable treatment.

When buying Metronidazole 400mg tablets online, you should always ensure you are purchasing from a fully regulated UK pharmacy. To learn more about our company and who we are regulated by, visit our about us page.

Metronidazole Dosage

All of our Doctors and Pharmacists follow NICE guidelines when prescribing Metronidazole.

Always take Metronidazole exactly as instructed by your doctor or pharmacist. Read the patient information leaflet thoroughly before you start to use this treatment. Speak to your doctor or pharmacist for more information if you are not sure of how to take it.

Metronidazole FAQ's

Where can I buy Metronidazole tablets over the counter?

This medicine is prescription-only, so you can only purchase it from a pharmacy when you have spoken to a doctor. If you use Medicine Direct, one of our certified doctors can issue you a prescription for Metronidazole if they deem it a suitable medicine for your infection.

If you order before 2pm, we can have your medicine with you in 24 hours, as next day delivery is available. Never buy any medicine online unless it is from a pharmacy that is registered with the General Pharmaceutical Council, like Medicine Direct. All of our doctors are registered with the General Medical Council, which means they can prescribe you medicine just like your local GP.

How many Metronidazole tablets do I need to take to treat bacterial vaginosis?

You should take 1 tablet twice a day for 7 days. Keep taking the tablets even if your symptoms start to go away. This will ensure the infection is properly fought by the medicine. You will need 14 Metronidazole 400mg tablets for this treatment; at Medicine Direct, we sell packets of 14 tablets in the 400mg strength dose.

Do I take Metronidazole tablets with or after food?

You should take these Metronidazole tablets after you have eaten food.

Can I drink alcohol with Metronidazole?

No, you should not drink alcohol at the same time as using this medicine. Alcohol can cause nausea/vomiting when drank at the same time as using Metronidazole. Do not drink alcohol for at least 48 hours after you finish taking this medicine.

My symptoms have got better but haven't cleared completely. What do I do now?

This is quite common for women who are suffering from bacterial vaginosis. If your initial course of treatment is unsuccessful, you may require a second course. If this is the case, make sure that you took the first course correctly and consistently, and speak to your doctor about getting a second course of treatment.

Will it interfere with my contraceptive pill?

Metronidazole will not interfere with any form of contraception, including the emergency contraception pill and the combined contraception pill. However, if you suffer from vomiting or severe diarrhoea for more than 24 hours, your contraception pills might not be effective. If this happens to you while you are taking this medicine, refer to the information leaflet which will come with your contraception medication.

Can I have sex while I am receiving treatment for bacterial vaginosis?

To avoid upsetting the pH balance in the vagina and risk worsening your symptoms, it is best to avoid having sex until your infection has cleared completely.

Why is Metronidazole contraindicated in alcoholic patients?

If you take this medicine with alcohol, it can result in a serious reaction, including vomiting and nausea. For this reason, this medication is not recommended for individuals who have problems with alcohol.

If you do not have any alcohol problems, it is still important you do not drink it for the duration of your treatment, to prevent side effects. Do not drink alcohol for at least 2 days after your final dose of Metronidazole.

Will it affect my period?

This medicine is only taken for a short time, therefore it should not affect your period. Some antibiotics can have an effect on a woman's period by lowering her oestrogen levels (the hormone which causes the menstrual cycle). This may result in a delay in your period, or your ovulation may occur at a later date than usual.

What happens if bacterial vaginosis is left untreated?

This infection is not likely to lead to any other health problems. However, if left untreated, it may increase your risk of catching certain sexually transmitted infections, such as herpes or chlamydia. It can also lead to pelvic inflammatory disease, leading to an infection of the Fallopian tubes or uterus.

Does Metronidazole have side effects?

Like all medicines, Metronidazole does have side effects, although they will not affect everyone. A list of adverse effects can be found on the Side Effects tab of this page; there is also another list on the homepage. Always read the patient information leaflet, which will come with your medicine, for a full list of side effects you might suffer.

Which is better: Metronidazole gel or tablets?

The cream/gel version of this treatment works effectively to treat BV. A single dose of the cream/gel is applied inside the vagina at bedtime for a period of five days. The tablet has similar results at the end of treatment, but it is thought that the vaginal treatment may have fewer side effects. However, many women prefer to use the tablets.

Metronidazole Side Effects

Milder Metronidazole side effects can be found on the main page.

Contact your doctor as soon as possible if you experience any of the following side effects while taking Metronidazole:

  • Liver problems, including liver failure (this could be life-threatening)
  • Dark urine
  • Skin rash or flushing
  • Feeling dizzy or sleepy
  • Headaches
  • Muscle or joint pain
  • Mental problems such as confusion or hallucinations
  • Eyesight issues, such as blurred vision or double vision
  • Yellowing of the skin or eyes (these could be signs of a liver problem)
  • Unexpected infections, mouth ulcers, bleeding gums, bruising
  • Severe stomach pain, which may spread to your back (you could have pancreatitis)
  • You have a fever that is higher than 38C, a stiff neck, you are hallucinating, feel confused, have trouble speaking, or cannot cope with bright light
  • Loss of appetite
  • You feel depressed
  • Hearing problems or loos of hearing
  • Tinnitus
  • Numbness, weakness, or tingling in the arms or legs

Having a fever, stiff neck, feeling confused, hallucinations, sensitivity to bright light or difficulty speaking may appear together, or you may experience a few of these symptoms. These could be signs of meningitis; it is very important you contact your doctor immediately if you exhibit any of these symptoms.

Serious allergic reaction

In rare cases, you could suffer a serious allergic reaction to this medicine. This could result in you requiring immediate treatment in hospital.

You must either go to A&E or call 999 straight away if you exhibit any of the following symptoms while you use Metronidazole:

  • You are wheezing
  • You develop a skin rash that is red, itchy, swollen, blistered, or peeling skin
  • You have swelling in your face, throat, lips, tongue, or mouth
  • You have tightness in your chest or throat
  • You are finding it difficult to breathe or speak

The above lists may not be exhaustive. For a comprehensive list of side effects, please always read the patient information leaflet, thoroughly, before you start to use a new medicine.

If you have any questions or concerns about adverse reactions, please discuss them with your doctor or pharmacist.

Metronidazole Warnings and drug interactions

Metronidazole may interact with other medicines in both adults and children, which can increase your risk of side effects or hinder its effectiveness.

Before you start to use a new medicine, it is very important you tell your doctor if you are currently taking, or have recently taken, any other medicines. This includes both prescription and non-prescription medication, vitamins, supplements and herbal remedies.

In particular, when you use Metronidazole tablets, you should inform your doctor if you are already taking any of the below medicines:

  • The blood thinning medicine warfarin
  • Lithium to treat mental illness
  • Disulfiram for treating alcoholism
  • The epilepsy medicines phenytoin or phenobarbitone
  • Medicines for the treatment of cancer, fluorouracil or busulfan
  • Any medicines that you take as a liquid (many liquid medicines contain alcohol)

Metronidazole is not known to cause any problems when taken alongside herbal remedies. Nonetheless, you should still inform your doctor if you are currently using any herbal remedies, vitamins or supplements, as several contain alcohol.

Please read the patient information leaflet, which will accompany your tablets, for comprehensive information on the warnings and drug interactions associated with Metronidazole.

If you have any doubts as to whether this medication is suitable for you, please do not hesitate to speak to your doctor or pharmacist before you begin your course of treatment.

Driving and operating machinery

This medicine will not have a direct impact on your ability to drive, ride a bike, or operate machinery. However, as nausea, vomiting, hallucinations and dizziness are all associated reactions with this medicine, you should not drive, operate machinery, or cycle if you experience any of these effects.

If you do experience these reactions, wait until you feel better before you drive, cycle or operate machinery.

If your symptoms persist, speak to your doctor for advice.

Metronidazole Ingredients

The active ingredient contained in this medication is metronidazole.

Inactive ingredients also contained in the tablets are: calcium hydrogen phosphate (E341), starch maize, povidone K30 (E1201) and magnesium stearate.

Delivery Company Delivery Service Price Details
Royal Mail UK Delivery Standard UK Tracked £2.99 3 - 4 Working Day Delivery
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DPD UK Next Day Delivery Tracked Saturday Delivery £9.95

Delivery specified for Saturday

Order Friday by 2pm (subject to Dr approval)

Please note that next day delivery to Northern Ireland, Scottish Highlands & Islands and British Isles cannot be guaranteed. Please contact our team for more information.

This page has recently been medically reviewed by Hussain Abdeh MPharm: 2211840

Updated on: 18/06/2021

This content has been written by our Superintendent Pharmacist Hussain Abdeh and has been medically reviewed by our Pharmacist Sonia Khan

Hussain Abdeh Superintendent Pharmacist at Medicine Direct

Hussain Abdeh
MPharm: 2211840

Pharmacist Independent Prescriber

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