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Vermox, Ovex

Carefully read and follow the directions from the pack.

Everyone in your family should be treated on the same day.

Side-effects are uncommon but may include tummy (abdominal) pain and diarrhoea.

Follow the few simple hygiene rules that will help prevent re-infection. Most importantly, wash your hands and scrub your nails after visiting the toilet and before eating meals.

Continue reading below

About mebendazole

Type of medicine


Used for

Treatment of roundworms (particularly threadworms) in adults and in children over 2 years of age

Also called

Vermox®; Ovex®

Available as

Oral liquid medicine and chewable tablets

Roundworms are worms with a long, round (tubular) body. They are parasites of humans, which means that they can live in our bodies. Threadworms, hookworms and whipworms are all types of roundworm.

Threadworms are a relatively common type of roundworm and can be easily passed from one person to another, but they do not usually cause serious problems. They live inside the bowel for a short time - adult threadworms do not live for longer than six weeks. The female worm lays her eggs at night around an infected person's back passage. This causes irritation and an 'itchy bottom'. If the person then scratches the area it allows the tiny eggs to get under the fingernails. If the fingers are then put in the mouth - for example, during sleep - the eggs may be swallowed. The worms then develop in the gut and produce more eggs. Eggs can easily get on to bedding, carpets and towels, and into house dust. They can also get on to food and be swallowed. All this creates a cycle of re-infection.

Other types of roundworm eggs live in the soil in tropical countries. They most commonly get into the body when a person gets them on his or her hands and then transfers them to their mouth. This can lead to a cycle of infection, and any food which is handled can become contaminated. Roundworm infections can be a problem for people living in, or travelling to, a tropical country, and for those who eat contaminated food.

Mebendazole works by preventing the worms from absorbing sugars which they need to survive. This kills the worm within a few days. Although mebendazole kills adult worms, it does not kill the eggs. Because of this it is important to break the cycle of re-infection. This can be done by treating everyone living in your house at the same time (even if they do not have any symptoms), and by following the advice given in the section below called 'Getting the most from your treatment', to prevent re-infection.

Mebendazole is available on prescription. You can also buy it without a prescription in pharmacies.

Before taking mebendazole

To make sure this is the right treatment for you or your child, before taking mebendazole it is important that your doctor or pharmacist knows:

  • If you are pregnant or breastfeeding.

  • If you have a baby or young child in the family. You cannot buy mebendazole for use in children under 2 years old - you will need advice from a doctor.

  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.

  • If you have ever had an allergic reaction to a medicine.

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How to take mebendazole

  • Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. The manufacturer's leaflet will give you more information about mebendazole and a full list of the side-effects which you may experience from taking it.

  • Follow the dosage instructions carefully and make sure all members of your family are treated on the same day, even if they do not appear to be infected.

  • In the UK the most common worm infection is threadworm - this is a type of roundworm and is sometimes referred to as a pinworm. For threadworm infections, you will need to take one dose of 100 mg (one tablet or 5 ml of liquid medicine).

  • It is highly recommended to take a second 100 mg dose 14 days later to kill any worms that have hatched since the last treatment. This is especially important if you suspect you (or your child) may have become re-infected.

  • Your dose will be different to this if you are prescribed mebendazole for any other type of roundworm infection.

  • Mebendazole can be taken before or after food. The tablets can be chewed, crushed, or swallowed whole.

Getting the most from your treatment

Mebendazole removes roundworms, but not their eggs. Therefore, it is also important to break the cycle of re-infection which can occur - this can be done by following a few simple hygiene measures to prevent you from swallowing eggs, causing a new infection:

  • Wash your hands and scrub your nails with a nailbrush after every visit to the toilet, and before preparing or eating a meal.

  • Wear underwear or pyjamas in bed.

  • Have a bath or shower, immediately after waking up in the morning, to wash away any eggs that have been laid during the night.

  • Disinfect your toilet seat and toilet handle, and the handle on your toilet door, regularly.

  • Vacuum the carpets in your bedrooms every day, and wet-wipe the surfaces of your bedroom furniture.

  • Keep your fingernails short and clean, and avoid biting your nails or sucking your fingers.

  • Have a separate towel for each member of your family to use.

  • Change and wash your clothing and bedding frequently.

Continue reading below

Can mebendazole cause problems?

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the ones associated with mebendazole. You will find a full list in the manufacturer's information leaflet supplied with your medicine.

Mebendazole side-effects

What can I do if I experience this?

Tummy (abdominal) discomfort, diarrhoea, wind

If troublesome, speak with your doctor or pharmacist

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

How to store mebendazole

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

Important information about all medicines

Important information about all medicines

If you buy any medicines check with a pharmacist that they are safe to take with your other medicines.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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