mebendazole
Benzimidazole anthelmintic· Brands: Vermox, OvexPO
Mechanism of action
Mebendazole binds to tubulin in susceptible parasites and prevents microtubule assembly. This interferes with glucose uptake and energy metabolism, causing the parasite to die. It is active against adult and larval stages of many intestinal nematodes.
Pharmacokinetics
Mebendazole is poorly absorbed after oral administration, with less than 10% systemic availability. The absorbed portion is mainly metabolised in the liver. Most of the dose is excreted unchanged in faeces. Its low bioavailability helps target the gut lumen.
Indications & dosing
Enterobiasis (pinworm)
Repeat after 2 weeks to prevent reinfection.
- adult · PO: 100 mg single dose · Repeat after 2 weeks to prevent reinfection.
Ascariasis (roundworm)
Give for 3 days.
- adult · PO: 100 mg twice daily · Give for 3 days.
Hookworm
Give for 3 days.
- adult · PO: 100 mg twice daily · Give for 3 days.
Whipworm (trichuriasis)
Give for 3 days.
- adult · PO: 100 mg twice daily · Give for 3 days.
Hydatid disease (echinococcosis)off-label
Specialist use; duration typically 3-6 months.
- adult · PO: 400 mg Hydatid disease (echinococcosis), ADULT PO: 400-500 mg three times daily, maxDailyDose 1500 ("Specialist use; duration typically 3-6 months.") · Specialist use; duration typically 3-6 months.
Contraindications & precautions
- Hypersensitivity to mebendazole or any component of the formulation
- Pregnancy (particularly first trimester) · Use only if clearly indicated and benefit outweighs risk, caution in later trimesters
- Children under 2 years of age · Lack of safety data, use with caution and specialist advice
- Monitor liver function in patients receiving prolonged or high-dose therapy (e.g., for echinococcosis).
- Use with caution in hepatic impairment, as dose reduction or avoidance may be necessary.
- Assess for contact with infected individuals and treat concurrently to prevent reinfection.
- Check for drug interactions, particularly with cimetidine, which may increase plasma concentrations.
- Avoid alcohol during treatment as it may increase the risk of hepatotoxicity.
Adverse effects
- Abdominal pain
- Diarrhoea
- Flatulence
- Headache
- Dizziness
- Rash
- Elevated liver enzymesserious
- Hepatitisserious
- Agranulocytosis or neutropeniaserious
- Severe cutaneous adverse reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis)serious
Monitoring, pregnancy & toxicity
- Liver function tests · Baseline and during prolonged therapy (e.g., for hydatid disease)
- Full blood count · During prolonged therapy
- Pregnancy: Mebendazole is contraindicated in pregnancy, particularly the first trimester, due to teratogenic potential. Use only if the potential benefit justifies the risk to the fetus.
- Toxicity: Gastrointestinal symptoms (abdominal pain, nausea, vomiting, diarrhoea) · Discontinue therapy, provide supportive care, maintain hydration.
- Toxicity: Elevated liver enzymes (uncommon) · Withdraw the drug; monitor liver function until normalisation.
- Toxicity: Hypersensitivity reactions (e.g., rash, angioedema) · Stop treatment; give antihistamines or corticosteroids if required.
Clinical notes
Mebendazole is used for the treatment of common intestinal helminth infections, including pinworm, threadworm, roundworm, hookworm and whipworm. Doses vary by indication and local guidelines. For example, pinworm is often treated with a single dose, repeated after two weeks. It is generally well tolerated, with occasional abdominal pain or diarrhoea. Avoid in pregnancy unless the benefit outweighs risk. Check for interactions with enzyme inducers such as carbamazepine and phenytoin.
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BNF; local formulary