Mebendazole
Vermox, Ovex
Peer reviewed by Sid DajaniLast updated by Michael Stewart, MRPharmSLast updated 26 Mar 2023
Meets Patient’s editorial guidelines
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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.
At a glance
Mebendazole is a medicine used to treat roundworm infections, including threadworms.
It works by preventing worms from absorbing sugars, which kills them within days.
For threadworms, you generally take one dose, and a second dose 14 days later.
Mebendazole does not kill eggs, so good hygiene is essential to prevent re-infection.
It is available as a liquid or chewable tablets, and can be bought without a prescription.
Common side-effects include tummy discomfort, diarrhoea, and wind.
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Video picks for Infection treatment medicine
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About mebendazole
Type of medicine | Anthelmintic |
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
Back to contentsTo 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
Back to contentsBefore 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
Back to contentsMebendazole 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.
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Can mebendazole cause problems?
Back to contentsAlong 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
Back to contentsKeep 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
Back to contentsImportant 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.

Unsure about mixing medicines?
Check for possible interactions between medicines, supplements and foods before taking them together.
Frequently asked questions
Can I use mebendazole for my child who is under 2 years old?
No, mebendazole is not recommended for children under 2 years old unless advised by a doctor. If you have a baby or young child in the family, you'll need to seek advice from a medical professional before giving them mebendazole.
Why is it important to treat everyone in my household for threadworms at the same time?
Threadworms can easily be passed from one person to another, and even if someone doesn't show symptoms, they could still be carrying the worms. Treating everyone in the house simultaneously helps to break the cycle of re-infection and prevent the worms from spreading further.
What is the difference between taking mebendazole for threadworms versus other types of roundworms?
For threadworm infections, the standard dose is one 100 mg tablet or 5 ml of liquid medicine, with a second dose recommended 14 days later. If you have a different type of roundworm infection, your doctor will prescribe a different dose and treatment plan.
How quickly does mebendazole kill the worms?
Mebendazole works by stopping the worms from absorbing the sugars they need to survive. This process kills the adult worms within a few days of taking the medicine.
Can mebendazole be taken with other medicines?
Before taking mebendazole, it's important to tell your doctor or pharmacist about any other medicines you are taking, including those available without a prescription, as well as herbal and complementary medicines. This ensures there are no potential interactions.
What should I do if I forget to take the second dose of mebendazole after 14 days?
While the article highly recommends taking a second 100 mg dose 14 days later to kill any newly hatched worms, it doesn't specify what to do if a dose is missed. Consult your doctor or pharmacist for advice if you miss this important follow-up dose, especially if you suspect re-infection.
Are tropical roundworm infections treated with the same dose of mebendazole as threadworms?
The article states that your dose will be different if you are prescribed mebendazole for any type of roundworm infection other than threadworms. This suggests that other roundworm types, including those from tropical countries, would require a specific dosage tailored by a doctor.
Further reading and references
- Manufacturer's PIL, Vermox® 100 mg tablets; Janssen-Cilag Ltd, The electronic Medicines Compendium. Dated January 2021.
- Manufacturer's PIL, Vermox® 100 mg/5 ml oral suspension; Janssen-Cilag Ltd, The electronic Medicines Compendium. Dated January 2021.
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About the authorView full bio

Michael Stewart, MRPharmS
Medicine Leaflet Review Manager – Contractor, Pharmacist
BPharm (Hons), MRPharmS
Michael is a community pharmacist practicing in the Midlands and South Yorkshire with more than 20 years’ experience advising on medicines and medical conditions. He has a strong background in healthcare training, having produced and delivered training courses for pharmacy teams and staff of residential care settings, including nurses. He has also contributed to pharmacy advisory boards for the management of low acuity conditions in the community.
About the reviewer

Sid Dajani
Sultan Dajani qualified at the London School of Pharmacy in 1994 and became the youngest elected member of the Royal Pharmaceutical Society council since its founding in 1842.
Article history
The information on this page is written and peer reviewed by qualified clinicians.
Next review due: 25 Sept 2027
26 Mar 2023 | Latest version

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