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.

• 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.

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

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.

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

Serious allergic reaction

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

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

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.

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.

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.