9.6.2 Antiparasitic Drugs Targeting HelminthsA variety of structurally diverse compounds is used to eradicate or at least reduce the
numbers of helminthic parasites in the intestinal tract or tissues of the body. The search
for antihelminthics has been somewhat less systematic than for other microbial
pathogens. Most of these agents were discovered by traditional screening programs;
their mechanisms of action at a molecular level are frequently unknown.
Albendazole (9.117), a benzimidazole carbamate, is a broad-spectrum oral anti-
helminthic used for cysticercosis, ascariasis, pinworm infestation, and hookworm infes-
tation. It is thought to work by blocking microtubule synthesis in the nematode,
subsequently impairing glucose uptake.
Diethylcarbamazine citrate (9.118), a synthetic piperazine derivative, is used for the
treatment of filariasis and loiasis. Although its mechanism of action is basically
unknown, it appears to somehow alter the surface structure of the helminth, rendering
it more susceptible to destruction by the host defenses.
Ivermectin (9.119), a semisynthetic macrocyclic lactone, is the drug of choice for
strongyloidiasis and onchocerciasis types of helminth infestation. Ivermectin appears to
paralyze the nematode, which may lead to its death but which certainly facilitates its
expulsion from the body.
588 MEDICINAL CHEMISTRY