Anti-infective
Anthelmintics
Anti-worm / antiparasitic medicines — Medicines that treat worm (helminth) infections — from common threadworm in UK children to roundworm, tapeworm and tropical worms.
Education and reference only. This is a plain-language class overview — it deliberately contains no doses. Always check the current Summary of Product Characteristics (SmPC), the BNF and your local formulary before prescribing or administering any medicine.
Quick answer
What is Anthelmintics?
Anthelmintics treat infections caused by parasitic worms (helminths). The commonest use in the UK is threadworm, which is very common in children and easily passed around households, treated with a medicine such as mebendazole alongside strict hygiene measures and usually treating the whole household.
- How it works: These medicines kill or paralyse worms so they can no longer feed or anchor in the gut and are then passed out of the body.
- In practice: In practice, threadworm is managed in the community: treat everyone in the household at the same time, repeat after an interval because the medicine does not kill the eggs, and pair this with hygiene measures — handwashing, short nails, morning showers and hot-washing bedding and nightwear.
What it is
Anthelmintics treat infections caused by parasitic worms (helminths). The commonest use in the UK is threadworm, which is very common in children and easily passed around households, treated with a medicine such as mebendazole alongside strict hygiene measures and usually treating the whole household. Other worms — roundworm and tapeworm — and a range of tropical worm infections are treated with related drugs, some of which are reserved for specific parasites and given under specialist advice.
How it works
These medicines kill or paralyse worms so they can no longer feed or anchor in the gut and are then passed out of the body. Different drugs suit different worms: mebendazole and albendazole stop the worm taking up glucose, pyrantel and levamisole paralyse the worm, praziquantel is used for tapeworms and flukes, and ivermectin and diethylcarbamazine target particular tropical infections. Because threadworm eggs are easily re-swallowed, hygiene measures are part of the cure and a second dose is often needed to catch newly hatched worms.
In practice
In practice, threadworm is managed in the community: treat everyone in the household at the same time, repeat after an interval because the medicine does not kill the eggs, and pair this with hygiene measures — handwashing, short nails, morning showers and hot-washing bedding and nightwear. Most courses are short and very well tolerated. Drugs for tropical worm infections such as ivermectin, praziquantel and diethylcarbamazine are used under specialist guidance, sometimes with caution where heavy parasite loads or co-infections raise the risk of reactions. Pregnancy generally calls for non-drug hygiene measures first and specialist advice before any anthelmintic.
Examples
Practical use
How to take it & use it well
- Treat everyone in the household on the same day, even those with no symptoms, because threadworms spread easily and others are often infected without realising it.
- Take the recommended treatment as directed, and follow it with strict hygiene for around two weeks to break the cycle of reinfection.
- Wash hands and scrub under the nails carefully, especially after using the toilet and before eating, as eggs are picked up on the fingers and swallowed.
- Keep nails short, discourage scratching around the bottom and nail-biting, and wear close-fitting underwear at night.
- On the morning after treatment, hot-wash bedding, nightwear and towels, and damp-dust or vacuum bedrooms to remove any eggs.
- For young children or in pregnancy, focus on rigorous hygiene measures and ask a pharmacist or GP before using any medicine.
Common uses
- Threadworm (whole-household treatment plus hygiene)
- Roundworm and other intestinal worms
- Tapeworm infections
- Tropical worm infections (specialist-directed)
Monitoring
- Symptom resolution and, for some infections, repeat stool testing
- Specialist follow-up for tropical or heavy infections
- Watch for reactions when treating high-burden infections
Weighing it up
Advantages & disadvantages
Advantages
- A single recommended treatment combined with hygiene clears most infections effectively.
- Treatment is available from pharmacies and is simple to take at home.
- Threadworms are harmless to general health in most cases and are usually easy to deal with.
- Treating the whole household at once greatly reduces the chance of it returning.
- Hygiene measures alone can manage cases where medicine is not suitable, such as in very young children.
Disadvantages
- Reinfection is common if hygiene is not kept up for the full couple of weeks.
- The treatment is not always recommended for very young children or in pregnancy, where hygiene comes first.
- It can be unsettling and may need repeating if the household is not all treated together.
- The intense hygiene routine takes effort and consistency from the whole family.
- Itching can persist briefly even after the worms are gone.
Key safety principles
What to watch for
- For threadworm, treat the whole household at once and combine with hygiene measures, as the medicine does not kill the eggs.
- A repeat dose after an interval is often needed to clear newly hatched worms.
- Some agents (e.g. ivermectin, praziquantel, diethylcarbamazine) are for specific tropical infections and used on specialist advice.
- Pregnancy and breastfeeding restrict which agents are suitable — seek advice before treating.
- Heavy worm burdens can cause reactions as parasites die, sometimes needing specialist supervision.
Key interactions
What to avoid or check alongside
- The medicine is mostly intended as a short course, so significant interactions are uncommon, but always tell the pharmacist about other regular medicines.
- Skipping the hygiene steps undermines the medicine and is the main reason treatment appears to fail.
- Not treating the whole household at the same time allows the infection to pass back and forth between people.
Patient & carer advice
- Treat everyone in the home at the same time for threadworm and repeat as advised
- Wash hands and scrub under nails, especially before eating and after the toilet; shower in the morning
- Hot-wash bedding, towels and nightwear and vacuum to remove eggs
- Short courses are usually very well tolerated — report any unexpected or severe symptoms
Answers
Anthelmintics: frequently asked questions
Why do I need to treat the whole family?
Threadworms spread very easily and people can carry them without symptoms. Treating everyone on the same day stops the infection bouncing between household members and coming back.
How do I stop threadworms coming back?
Combine treatment with strict hygiene for about two weeks, including thorough handwashing, keeping nails short, hot-washing bedding and avoiding scratching. This breaks the cycle of swallowing eggs and reinfecting yourself.
Can I treat threadworms in pregnancy?
In pregnancy the usual advice is to rely on strict hygiene measures rather than medicine, at least for a while. Ask a pharmacist or GP before using any treatment so they can advise what is safe for you.
How are threadworms spread?
Eggs around the bottom are picked up on the fingers, often through scratching, and then swallowed or passed to surfaces and other people. Good handwashing and short nails are key to stopping this.
Do I need to see a doctor for threadworms?
Most cases can be treated with a pharmacy product and hygiene measures. Seek advice for young children, in pregnancy, or if the problem keeps returning despite treatment.
Authoritative sources
Always verify against the source
This overview is for orientation. For doses, interactions, contra-indications and the full monograph, use:
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Common anthelmintics by active ingredient
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