Antihelmintics

Antihelmintics are drugs used to treat infections caused by helminths, including nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes). They are used in human and veterinary medicine and are chosen according to the parasite species and the site of infection. Treatment aims to eradicate parasites, relieve symptoms, and reduce transmission, often with single-dose or short-course regimens.

Common agents are grouped by mechanism. Benzimidazoles such as albendazole and mebendazole inhibit microtubule synthesis in helminths, impairing glucose uptake and leading to death. Praziquantel increases parasite cell membrane permeability to calcium, causing rapid paralysis and detachment of the tegument in cestodes and trematodes. Ivermectin and related avermectins bind to glutamate-gated chloride channels, producing paralysis and death of microfilariae and some intestinal nematodes. Pyrantel pamoate acts as a nicotinic acetylcholine receptor agonist, causing depolarizing neuromuscular blockade in nematodes. Niclosamide uncouples oxidative phosphorylation in many cestodes. Diethylcarbamazine is active against filarial worms, while nitazoxanide has broader activity including some protozoa and helminths.

Indications include intestinal nematodes such as Ascaris and hookworms; tissue nematodes (strongyloides, filariae); cestodes such as Taenia; and trematodes including Schistosoma. Administration is usually oral, with dosing guided by species and burden; some agents are available in combination or as topical formulations in select regions.

Resistance and safety concerns exist, including variable efficacy, adverse effects (GI symptoms, fever, hypersensitivity), and drug interactions. Use during pregnancy and in children requires risk-benefit assessment. Public health programs employ mass drug administration in endemic areas to control transmission.