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Pharmacology · Anthelmintics

Mebendazole !

A benzimidazole that is barely absorbed: it acts in the gut lumen against roundworm, whipworm, hookworm and pinworm.

Updated 2026-11-01

  • Class: Anthelmintics
  • Target: Helminth β-tubulin (colchicine site)
  • ATC code: P02CA01
  • WHO Model List of Essential Medicines

The figure shows mebendazole itself bound to bovine tubulin at the colchicine site; in the worm it binds the same β-tubulin site, with higher affinity than for mammalian tubulin.

Target in 3D: Helminth β-tubulin (colchicine site). PDB structure 7ODN (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

It binds worm β-tubulin and stops microtubules from forming. The parasite's intestinal cells stop taking up glucose, its energy runs out and the worm dies and is expelled. Because so little is absorbed, it acts mainly in the gut lumen.

  1. Reaches the gut lumen almost intact
  2. Binds worm β-tubulin
  3. No microtubules and no glucose uptake
  4. The worm runs out of energy and is expelled

Pharmacokinetics

Absorption
Very low orally, from poor absorption and extensive first-pass metabolism
Distribution
The little that is absorbed is highly bound to plasma proteins
Metabolism
Extensive liver metabolism to metabolites without anthelmintic activity
Elimination
Almost all in faeces; a tiny fraction in urine

Indications

Adverse effects

Common

  • Abdominal pain and diarrhoea, mainly in heavy infections as worms are expelled
  • Nausea, vomiting and loss of appetite
  • Rash and hives (uncommon)

Contraindications

  • Hypersensitivity to mebendazole
  • First trimester of pregnancy (not recommended in pregnancy outside WHO programmes)

Key interactions

Cimetidine
May inhibit its metabolism and raise its blood levels

What is monitored

  • In prolonged treatment: periodic blood count and liver function
  • Laboratory tests to check the response to treatment

Administration and safety

  • Oral chewable tablet.
  • Does not work for hydatid disease or Strongyloides: confirm the indication.
  • Name looks like albendazole: they are not interchangeable for tissue infections.

Nursing care

  • Hygiene teaching: frequent handwashing to prevent reinfection and spread.
  • Ask about pregnancy before giving it.
  • Report seizures, rash, hives, difficulty breathing, or fever with sore throat.
  • In pinworm, explain that reinfection is common and household hygiene matters.

Pregnancy and breastfeeding

Embryotoxic in rats and the label does not recommend it in pregnancy; WHO uses it for deworming pregnant women in the second and third trimesters.

Test yourself

Think of the answer, then tap the question to see it.

Why does mebendazole not work for hydatid disease?

Because it is barely absorbed: it acts in the gut lumen and does not reach tissue cysts well.

Which soil-transmitted helminths does mebendazole treat?

Ascaris lumbricoides, Trichuris trichiura and hookworms, as well as Enterobius vermicularis.

Which drug can raise mebendazole levels?

Cimetidine, which may inhibit its metabolism.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - MEBENDAZOLE tablet, chewable (DailyMed (U.S. National Library of Medicine), 2026); Mebendazole: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); Soil-transmitted helminth infections (World Health Organization, 2023); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 68 (McGraw Hill, 2023).

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Representative model, for educational purposes only.