Diethylcarbamazine

Diethylcarbamazine is an oral piperazine derivative used for lymphatic filariasis, loiasis and tropical pulmonary eosinophilia. It is given once yearly, with albendazole, in mass drug administration for lymphatic filariasis in areas without onchocerciasis or loiasis. It kills microfilariae rapidly and causes inflammatory reactions that can be severe, so it is contraindicated in onchocerciasis and in heavy Loa loa infection.

Class. Anthelmintic; piperazine derivative (antifilarial).

Mechanism. Alters the surface of microfilariae so that host immune cells and platelets destroy them. It also affects arachidonic acid metabolism in the parasite.

Pharmacokinetics. Rapidly absorbed from the gut. Half life about 8 hours. Excreted mainly in urine, and elimination falls when urine is alkaline.

Lymphatic filariasis (individual treatment). 6 mg/kg orally once daily for 12 days, or as a single dose of 6 mg/kg.

Mass drug administration (lymphatic filariasis). 6 mg/kg single dose once yearly with albendazole 400 mg, in areas free of onchocerciasis and loiasis.

Loiasis. Start 50 mg on day 1, increase gradually to 6 mg/kg daily in 3 divided doses for 21 days; give prednisolone first and exclude high microfilaraemia.

Tropical pulmonary eosinophilia. 6 mg/kg daily in 3 divided doses for 14 to 21 days.

Loading dose, maintenance dose and titration. In loiasis, 50 mg on day 1 rising gradually to 6 mg/kg daily over several days. Maximum: 6 mg/kg daily.

Main alternatives. Ivermectin with albendazole for lymphatic filariasis where onchocerciasis is present; doxycycline for filarial disease.

Contraindications. Onchocerciasis (risk of severe skin and eye reactions); loiasis with high microfilaraemia (over 8000 microfilariae/mL, risk of encephalopathy); pregnancy; children under 2 years in mass treatment; severe acute illness.

Serious adverse effects. Encephalopathy and death in heavy Loa loa infection, severe Mazzotti-type reactions in onchocerciasis, hypersensitivity, and kidney or liver injury (rare).

Common adverse effects. Fever, headache, dizziness, nausea, vomiting, joint pain, itching and swollen glands (from killed parasites).

Interactions. Few documented; urinary alkalinising agents prolong its action.

Common prescribing errors. Giving in co-endemic onchocerciasis or loiasis areas without testing, and no corticosteroid cover in loiasis.

Special groups. - Pregnancy: avoid. - Breastfeeding: avoid. - Children: not under 2 years in mass treatment; dose by weight. - Older adults: usual dose. - Kidney impairment: reduce dose in severe impairment. - Liver impairment: caution.

Regional points. Lymphatic filariasis occurs along the coast of Kenya and Tanzania, but onchocerciasis and loiasis occur in parts of Uganda, Tanzania and Ethiopia, so ivermectin with albendazole is used for mass treatment in those areas instead of diethylcarbamazine.

Formulations. Tablets 50 mg and 100 mg.

Administration. After food, with water.

Baseline. Onchocerciasis and Loa loa exclusion by clinical and laboratory tests where endemic, pregnancy test, creatinine.

Monitoring. Symptoms for 3 days after the first dose; microfilarial clearance on blood film (night sample) at 6 to 12 months.

Stopping thresholds. Stop for confusion, drowsiness, severe skin or eye symptoms, or severe hypersensitivity.

Referral and escalation. Admission for neurological symptoms; specialist review for lymphoedema, hydrocele and tropical pulmonary eosinophilia.