Niclosamide

Niclosamide is an oral salicylanilide anthelmintic used for intestinal tapeworm infections. It is almost entirely unabsorbed, so systemic effects are rare, but it does not kill eggs. In Taenia solium infection, praziquantel is preferred, because release of eggs from dying worms can cause cysticercosis. Availability is now limited.

Class. Anthelmintic; salicylanilide.

Mechanism. Inhibits oxidative phosphorylation and anaerobic ATP production in the tapeworm scolex and proximal segments, which are then lost and digested.

Pharmacokinetics. Not absorbed from the gut. Most of the dose is excreted in faeces.

Taenia saginata, Diphyllobothrium latum (adults). 2 g (four 500 mg tablets) chewed as a single dose in the morning, after a light breakfast.

Children. Under 11 kg 500 mg; 11 to 34 kg 1 g; over 34 kg 1.5 g, as a single dose.

Hymenolepis nana. Adults 2 g once daily for 7 days; children 11 to 34 kg 1 g on day 1 and then 500 mg daily for 6 days.

Taenia solium. Not preferred; praziquantel is used, and if niclosamide is used, an antiemetic before and a purgative 1 to 2 hours after are given to prevent egg release into the stomach.

Loading dose, maintenance dose and titration. Not applicable. Maximum: 2 g in a single dose.

Main alternative. Praziquantel.

Contraindications. Hypersensitivity.

Serious adverse effects. None well documented; rare hypersensitivity.

Common adverse effects. Nausea, abdominal discomfort, loose stools, vomiting and itching.

Interactions. None of clinical importance, since it is not absorbed.

Common prescribing errors. Using it for Taenia solium without antiemetic and purge, swallowing tablets whole, and giving a second dose after worm passage without a check for the scolex.

Special groups. - Pregnancy: acceptable when needed because it is not absorbed. - Breastfeeding: compatible. - Children: dose by weight band. - Older adults: usual dose. - Kidney impairment: no adjustment. - Liver impairment: no adjustment.

Regional points. Praziquantel is more widely available than niclosamide in East Africa, so niclosamide is rarely used.

Formulations. Chewable tablets 500 mg.

Administration. Chewed thoroughly and swallowed with a little water, on a nearly empty stomach after a light meal; no further food for 2 hours.

Baseline. Species from proglottid or egg examination, pregnancy status.

Monitoring. Passage of the worm and scolex; stool examination for proglottids and eggs at 3 months.

Stopping thresholds. Not applicable for a single dose.

Referral and escalation. Specialist review for treatment failure, suspected cysticercosis and any neurological symptom.