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Written by Caidr's team of doctors and pharmacists based in UK | Updated: 26.01.2023 | 2 min read

Helminths are parasitic worms that can cause gut infection, and mebendazole is anthelmintic medicine designed to kill them. It’s available over-the-counter for adults and children aged 2 and over to treat threadworm, which causes an intense itch around the anus, especially in children under 10 years old.

On prescription, mebendazole can also be used to treat other parasitic worm infections such as roundworm, hookworm and whipworm. These infest the gut and are usually picked up from travel to certain countries.

How does it work?

Mebendazole kills parasitic worms by preventing them from obtaining glucose which is essential for their survival.

How do I take it?

Mebendazole comes in chewable tablet and oral liquid forms. Ovex is a branded version of mebendazole obtainable over-the-counter. To treat threadworm, everyone living in the same household should be given a single dose of mebendazole at the same time. This is either one tablet (which can be chewed, crushed or swallowed whole) or 5ml liquid. If reinfection is suspected a second dose should be taken after two weeks.

Mebendazole kills threadworms in the gut, but the worms lay eggs around the anus area. These eggs can survive for up to 2 weeks outside the body and can fall onto clothes, underwear, bedding, carpets and be caught up in dust, therefore effective hygiene measures are needed to prevent reinfection due to swallowing these eggs.

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Who should avoid mebendazole?

Do not take mebendazole if you have previously had an allergic reaction to mebendazole or another ingredient listed in the medication. If your child is under 2 years old and has threadworm, speak to their doctor first.

Speak with your doctor or pharmacist before taking mebendazole if you are pregnant or breastfeeding, intolerant to certain sugars or are taking medicines called metronidazole or cimetidine.

Any side effects? Anything else can I do?

Side effects can include stomach ache, diarrhoea, bloating and flatulence.

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