Albendazole is a synthetic nitroimidazole with a broad spectrum of antinematodal activity similar to mebendazole but with anticestodal and some antiprotozoal action. Mebendazole has had intermittent availability in the US, and its use has been supplanted by albendazole. Advantages of albendazole over mebendazole include its greater systemic absorption and its activity in a single oral dose of 400 mg (200 mg for children 1 to <2 years old) against ascariasis and hookworm infection and, to a lesser extent, enterobiasis and trichuriasis.

Albendazole is a benzimidazole carbamate that has a broad spectrum of anthelmintic activity, including against Ascaris lumbricoides, Enterobius vermicularis, Ancylostoma duodenale, Necator americanus, Strongyloides stercoralis, Echinococcus spp. and T. solium cysticerci. The drug has also been used to treat eosinophilic enterocolitis caused by Ancylostoma caninum, Capillaria philippinensis, cutaneous and visceral larva migrans, C. sinensis, Gnathostoma spinigerum, Oesophagostomum bifurcum and Trichostrongylus spp. It is also combined with diethylcarbamazine or ivermectin for mass treatment of lymphatic filariasis (Brugia malayi and Wuchereria bancrofti). Additionally, it has variable efficacy in treating microsporidiosis caused by Encephalitozoon hellem, E. cuniculi, E. intestinalis, E. bieneusi and Vittaforma corneae. Albendazole has some activity against G. lamblia.

Albendazole is used as monotherapy and in combination with a second agent. When used as initial therapy, albendazole has similar efficacy to metronidazole and other 5-nitroimidazoles. However, data on the use of albendazole in treating refractory cases show that it is most effective when combined with other agents. A small randomized controlled trial of 20 patients with nitroimidazole-refractory giardiasis compared albendazole monotherapy with albendazole–metronidazole combination therapy. Only 20% of patients were cured by monotherapy versus 90% receiving combination treatment. Other smaller studies have seen higher parasitologic cure rates in combination treatment and low cure rates with monotherapy, suggesting a synergistic effect.

The mechanism of action is similar to that of mebendazole with a blockade of parasite microtubule assembly. Albendazole is poorly soluble in water and should be taken with a fatty meal to enhance absorption. It undergoes extensive first-pass metabolism in the liver, and albendazole sulfoxide is responsible for most of the systemic anthelmintic effects. This metabolite has a half-life of 9–15 hours and is mostly excreted renally.