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Mebendazole

1. About mebendazole

Mebendazole is a type of medicine for treating worms.

It is used mainly for infections of the gut such as threadworms (sometimes known as pinworms) and other less common worm infections (whipworm, roundworm and hookworm).

You can buy mebendazole from a pharmacy. It's also available on prescription. It comes as chewable tablets or a liquid that you swallow.

2. Key facts

  • Mebendazole is usually taken as a single dose, but it can be taken for around 3 days for some infections.
  • The most common side effect is stomach pain.
  • You can buy mebendazole from a pharmacy for adults and children from the age of 2 years.
  • For children between 6 months and 2 years old, it is only available on prescription.
  • Common brand names include Vermox and Ovex.

3. Who can and cannot take mebendazole

Adults and children from the age of 2 years old can take mebendazole.

Younger children between the ages of 6 months and 2 years must be prescribed this medicine by a doctor.

Mebendazole isn’t suitable for some people. To make sure this medicine is safe for you, tell a pharmacist or doctor if you:

  • have had an allergic reaction to mebendazole or any other medicine in the past
  • are pregnant or breastfeeding

4. How and when to take it

Mebendazole comes as a banana-flavoured liquid and orange-flavoured tablets that can be chewed or swallowed whole.

How much should I take?

A doctor or pharmacist will tell you how much you should take depending on the type of worms you have.

Always follow the instructions that come with your medicine.

If you have threadworms (also called pinworms) you will usually take a single dose. If you live with anyone else, they will need to be treated at the same time because threadworms can spread easily.

A doctor or pharmacist may suggest you repeat the dose after 2 weeks to prevent you from getting them again. This is because the medicine kills the worms but not their eggs.

For other worms such as whipworm, roundworm and hookworm, follow a doctors’ instructions on how to take mebendazole. Usually you need to take a dose 2 times a day for 3 days.

How to take it

The tablet can be chewed or swallowed whole with a glass of water, juice or milk. You can take it with or without food.

The liquid comes with a spoon to measure it. If you don't have a spoon, ask your pharmacist for one. Do not use a kitchen teaspoon as it won't give you the right amount.

What if I forget to take it?

If you are taking mebendazole 2 times a day and you have missed a dose, take it as soon as you remember. However, if you remember more than 4 hours after your dose was due, skip the missed dose and just take your next dose as normal.

Do not take a double dose to make up for a forgotten one.

What if I take too much?

Taking an extra dose of mebendazole by accident is unlikely to cause any harm.

However, you may get side effects such as:

  • stomach cramps
  • feeling or being sick (nausea or vomiting)
  • diarrhoea

Speak to a doctor if you’re worried, have side effects or you take more than 1 dose.

Urgent advice: Call 111 for advice now if:

  • your child is under 2 years old and takes an extra dose of mebendazole

5. Side effects

Like all medicines, mebendazole can cause side effects, although not everyone gets them.

Common side effects

These side effects happen in more than 1 in 100 people.

Talk to a doctor or pharmacist if these side effects bother you or last more than a few days:

  • stomach pain
  • stomach discomfort including bloating and wind
  • diarrhoea

Serious side effects

Stop taking mebendazole and call a doctor straight away if you have:

  • blisters on your skin, mouth, eyes or genitals
  • yellow skin or the whites of your eyes turn yellow – these can be signs of liver problems

Immediate action required: Call 999 or go to A&E if:

  • you or your child has a fit or seizure

Serious allergic reaction

It happens rarely but it is possible to have a serious allergic reaction (anaphylaxis) to mebendazole.

Immediate action required: Call 999 or go to A&E if:

  • you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
  • you're wheezing
  • you get tightness in the chest or throat
  • you have trouble breathing or talking
  • your mouth, face, lips, tongue or throat start swelling

You could be having a serious allergic reaction and may need immediate treatment in hospital.

These are not all the side effects of mebendazole. For a full list see the leaflet inside your medicines packet.

Information:

You can report any suspected side effect to the UK safety scheme.

6. How to cope with side effects

What to do about:

  • stomach pain – try to rest. It can help to eat and drink slowly and have smaller and more frequent meals. Placing a heat pad or covered hot water bottle on your stomach may also help. If you are in a lot of pain, speak to a doctor or pharmacist.
  • stomach discomfort including wind – stick to simple meals and avoid rich or spicy food. It might help to take mebendazole after you’ve eaten to see if that helps ease the symptoms.
  • diarrhoea – drink plenty of water or other fluids to avoid dehydration. Signs of dehydration include peeing less than usual or having strong-smelling pee. Do not take any other medicines to treat diarrhoea without speaking to a pharmacist or doctor first.

7. Pregnancy and breastfeeding

Mebendazole isn't usually recommended for the treatment of threadworms during pregnancy or when breastfeeding. However if you have another worm infection such as roundworm or hookworm, you should speak to a doctor to discuss the best way to treat this.

If you're pregnant or breastfeeding, it is usually considered better to try to treat threadworms without taking a medicine. It's important to:

  • wash your hands and scrub under your fingernails – particularly before eating, after using the toilet or after changing nappies
  • bathe or shower every morning
  • rinse toothbrushes before using them
  • keep fingernails short
  • wash sleepwear, sheets and towels regularly
  • disinfect kitchen and bathroom surfaces
  • vacuum regularly and dust using a damp cloth

Find out more from BUMPS about how mebendazole can affect you and your baby during pregnancy.

Non-urgent advice: Talk to a pharmacist or doctor if you're:

  • trying to get pregnant
  • pregnant
  • breastfeeding

8. Cautions with other medicines

Some medicines and mebendazole interfere with each other.

Check with a pharmacist or doctor if you're taking:

  • metronidazole – a medicine usually used for bacterial or protozoan infections
  • cimetidine – usually used for excess stomach acid

Mixing mebendazole with herbal remedies or supplements.

There might be a problem with taking some herbal remedies and supplements together with mebendazole. Ask a pharmacist or doctor for advice.

Important

Tell a doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.

9. Common Questions

How does it work?

Mebendazole kills worms that cause gut infections such as threadworm (sometimes known as pinworm) and other less common worm infections (whipworm, roundworm and hookworm).

It works by stopping the worms using sugar (glucose). Without glucose, the cells of the worms lose their energy supply and quickly die.

Mebendazole does not kill the eggs of the worm. This is why you may need to take another dose 2 weeks later to help prevent reinfection.

How long does it take to work?

The medicine should start to work straight away but it may take several days to kill all the worms.

It is important that you take the medicine as a pharmacist or doctor tells you. Do not stop early if you have been told to take it for several days.

Mebendazole does not kill the worms' eggs, and these can cause you to get worms again and pass it on to other people.

A doctor or pharmacist may advise you to take mebendazole again after 2 weeks, to stop the worms from coming back.

Is it safe to take repeat doses (if worms keep coming back)?

Mebendazole does not kill the worms' eggs, and these can cause re-infection and also infect other people.

A doctor or pharmacist may advise you to take mebendazole again after 2 weeks, to prevent re-infection. However, if the infection comes back, speak to a doctor for advice.

It is also important to have good personal hygiene to stop the worms coming back.

A doctor or pharmacist may also advise that everyone in your house is treated with mebendazole.

Can I drink alcohol with it?

Yes, you can drink alcohol with mebendazole.

Is there any food or drink I need to avoid with this medicine?

You can eat and drink normally while taking mebendazole.

It is important to remember to wash your hands and scrub under your fingernails before eating to remove any eggs.

Will it affect my contraception?

Mebendazole doesn't stop contraceptive pills working, including the combined pill and emergency contraception.

But if mebendazole makes you sick or gives you severe diarrhoea for more than 24 hours, your contraceptive pills may not protect you from pregnancy.

If this happens, follow the instructions in the leaflet that comes with your contraceptive pills.

Find out what to do if you're on the pill and you're sick or have diarrhoea.

Will it affect my fertility?

There's no firm evidence to suggest that taking mebendazole will reduce fertility in either men or women.

But speak to a pharmacist or doctor before taking it if you're trying to get pregnant.

Can I drive or ride a bike?

Yes. Mebendazole shouldn't affect you being able to drive or cycle.

Are there any lifestyle changes that can help with threadworm?

It is important to have good personal hygiene to prevent threadworms from coming back, especially in babies and children under 2 years of age.

It's important to:

  • wash your hands and scrub under your fingernails – particularly before eating, after using the toilet or changing nappies
  • encourage children to wash their hands regularly
  • bathe or shower every morning
  • rinse toothbrushes before using them
  • keep fingernails short
  • wash sleepwear, sheets and towels regularly
  • disinfect kitchen and bathroom surfaces
  • vacuum rgularly and dust using a damp cloth
  • make sure children wear underwear at night – change it in the morning

Page last reviewed: 21 August 2019
Next review due: 21 August 2022