Albendazole

Albendazole is a broad-spectrum drug used against parasitic worms and certain protozoa, belonging to the benzimidazole class. It treats a wide range of intestinal infections, such as ascariasis, pinworm, hookworm, whipworm, strongyloidiasis, tapeworm infections, clonorchiasis, opisthorchiasis, cutaneous larva migrans, giardiasis, and gnathostomiasis.

Side effects

Common side effects include nausea, abdominal pain, and headache. Rare but serious risks include bone marrow suppression, which usually resolves after stopping the drug, and liver inflammation, especially in those with existing liver issues. In Australia, it is classified as pregnancy category D due to potential harm to a fetus.

Developed in 1975, albendazole is on the World Health Organization's List of Essential Medicines and comes in a fixed-dose combination with ivermectin. Its medical uses span flatworms and nematodes. For flatworms, it treats clonorchiasis, fasciolosis, and opisthorchiasis. Against tapeworms (cestodes), it serves as an alternative to praziquantel or niclosamide for adult beef and pork tapeworms, and is used for Taenia crassiceps infections.

Though praziquantel is often more effective for tapeworms, albendazole is more common in endemic areas due to lower cost and broader activity. It is the drug of choice for larval pork tapeworms causing cysticercosis, particularly neurocysticercosis, but does not affect old cysts. For echinococcosis of the liver, lung, or peritoneum caused by dog tapeworm larvae, or alveolar echinococcosis from Echinococcus multilocularis, albendazole is used when surgery is not possible; these cases may require lifelong treatment, as the drug only stops parasite growth and reproduction, not killing them.

For nematodes, albendazole treats many conditions. A single dose cures ascariasis. For baylisascariasis from raccoon roundworm, a 10-day course achieves 95–100% efficacy if started within 72 hours of egg ingestion, sometimes with corticosteroids for eye or central nervous system infections. In filariasis, it can cause allergic reactions from microfilariae breakdown, so antihistamines or corticosteroids may be added.

Ivermectin/albendazole

For lymphatic filariasis (elephantiasis) from Wuchereria bancrofti or Brugia malayi, it is given with ivermectin or diethylcarbamazine to suppress microfilaremia, and for Loa loa filariasis, it is an adjunct or replacement. Gnathostomiasis from Gnathostoma spinigerum requires 21 days of treatment, similar in effectiveness to ivermectin’s 2-day course. Hookworm infections, including cutaneous larva migrans from Ancylostoma, respond to a single dose. Strongyloidiasis is treated as an alternative to ivermectin or thiabendazole, sometimes with diethylcarbamazine.

Toxocariasis (visceral larva migrans) from dog or cat roundworms may need corticosteroids in severe cases or surgery for damage. Trichinosis from Trichinella spiralis or T. pseudospiralis is best treated early with albendazole, which has fewer side effects than thiabendazole; corticosteroids can prevent inflammation from dying larvae. Trichuriasis (whipworm) requires only a single dose and is sometimes considered the drug of choice. Giardiasis is an alternative to metronidazole, especially in children.

Medical uses

Microsporidiosis, including ocular cases from Encephalitozoon species, is treated with albendazole plus topical fumagillin. Granulomatous amoebic encephalitis from Balamuthia mandrillaris uses albendazole combined with miltefosine and fluconazole. For arthropods, it treats crusted scabies with topical crotamiton and salicylic acid, and intestinal myiasis, though ivermectin is far better for head lice. Despite its broad use, albendazole is FDA-approved only for hydatid disease from dog tapeworm larvae and neurocysticercosis from pork tapeworm larvae.

When given together, ivermectin and albendazole work synergistically: ivermectin paralyzes the parasite’s nervous and muscular systems, while albendazole disrupts its metabolism and microtubules by targeting tubulin polymerization. This dual action immobilizes and kills the parasite, improving treatment outcomes.