Albendazole

Albendazole is an oral benzimidazole anthelmintic with a broad spectrum covering roundworms, hookworms, whipworm, pinworm and strongyloides, and tissue infections such as neurocysticercosis and hydatid disease. It is also a key drug in mass drug administration for lymphatic filariasis. It is poorly absorbed in single doses, so tissue infections need long courses with fat and monitoring.

Class. Anthelmintic; benzimidazole.

Mechanism. The active sulphoxide binds beta-tubulin and blocks microtubule formation in the worm, impairing glucose uptake and causing energy depletion and death.

Pharmacokinetics. Poor absorption (under 5%) increased up to fivefold with a fatty meal. Rapidly converted in the liver to albendazole sulphoxide. Half life 8 to 12 hours. Excreted in urine and bile.

Ascariasis, hookworm, trichuriasis (adults and children 2 years and over). 400 mg orally as a single dose; for trichuriasis, 400 mg daily for 3 days, or combine with ivermectin.

Children 12 to 23 months. 200 mg as a single dose.

Enterobiasis. 400 mg single dose, repeated after 2 weeks.

Strongyloidiasis. 400 mg twice daily for 3 days; ivermectin is preferred.

Neurocysticercosis. 15 mg/kg daily (maximum 800 mg daily) in two doses with food for 8 to 30 days, with dexamethasone or prednisolone and antiepileptic cover; ophthalmic examination first.

Hydatid disease. 400 mg twice daily with food for 28 days, repeated in cycles with 14-day breaks, around surgery or drainage.

Lymphatic filariasis (mass drug administration). 400 mg once yearly with ivermectin 200 micrograms/kg (or diethylcarbamazine).

Loading dose, maintenance dose and titration. Not applicable. Maximum: 800 mg daily.

Main alternatives. Mebendazole, praziquantel, ivermectin.

Contraindications. Hypersensitivity to benzimidazoles; first trimester of pregnancy; untreated retinal cysticercosis.

Serious adverse effects. Hepatotoxicity, bone marrow suppression (neutropenia, pancytopenia) with prolonged courses, severe skin reactions, and inflammatory reactions with seizures and raised intracranial pressure in neurocysticercosis.

Common adverse effects. Headache, nausea, abdominal pain, dizziness and raised transaminases.

Interactions. Dexamethasone and cimetidine raise levels; carbamazepine, phenytoin and phenobarbital lower them; praziquantel raises albendazole sulphoxide.

Common prescribing errors. Treating neurocysticercosis without corticosteroids or without checking the retina, long courses without liver and blood tests, and giving in the first trimester.

Special groups. - Pregnancy: avoid in the first trimester; single-dose mass treatment is used after that. - Breastfeeding: compatible. - Children: single 200 mg dose at 12 to 23 months; 400 mg from 2 years. - Older adults: usual dose. - Kidney impairment: no adjustment. - Liver impairment: avoid in severe disease; monitor in mild to moderate.

Regional points. Albendazole is given to school children and under-fives in routine mass deworming across East Africa, and neurocysticercosis is a recognised cause of adult-onset epilepsy in areas where pigs roam free (parts of Tanzania, Uganda and Kenya).

Formulations. Tablets 200 mg and 400 mg (chewable); suspension 100 mg/5 mL.

Administration. Single doses with or without food; courses for tissue infection with a fatty meal.

Baseline. Liver tests and full blood count for courses longer than 3 days; pregnancy test; fundoscopy in suspected cysticercosis; imaging as indicated.

Monitoring. Liver tests and full blood count every 2 weeks during prolonged courses; neurological symptoms in neurocysticercosis.

Stopping thresholds. Stop for ALT over 3 times the upper limit of normal with symptoms, or over 5 times without; neutrophils under 1.0 x 10^9/L; severe skin reaction.

Referral and escalation. Specialist review for neurocysticercosis, hydatid disease and strongyloides in immunosuppressed patients.