Benzimidazoles

Agents: albendazole, mebendazole, thiabendazole

These drugs are used primarily to treat infections caused by helminthes (worms), ranging from the common pinworms found in children to pathogens causing massive cystic lesions in the brain. Most intestinal worm infections can be cured with a single dose of these drugs; for tissue-invasive disease,  prolonged courses are necessary.

Spectrum

Nematodes (roundworms): Ascaris lumbricoides  (roundworm),  Enterobius vermicularis (pin-worm), Necator americanus (hookworm), Strongyloides stercoralis (threadworm)

Cestodes (tapeworms): Echinococcus (liver abscess), Taenia solium (neurocysticercosis)

Adverse Effects

Albendazole and mebendazole are very well tolerated, especially when used as single-dose therapy in treatment of intestinal worm infection. With multidose regimens, adverse effects are primarily gastrointestinal, although hepatotoxicity and neutropenia are rarely reported. Thiabendazole is the most toxic and can cause CNS adverse effects.  These drugs should generally be avoided in pregnancy, although some data suggest that they may be safe after the first trimester.

Important Facts

• Although data are limited, these drugs appear to be substrates of the cytochrome P450 sys-tem. Thus, it is possible that co-administration with strong inducers of drug-metabolizing enzymes such as phenytoin and rifampin may lower serum levels. Oral absorption of albendazole and mebendazole is limited, which generally does not pose a problem for treatment of intestinal nematode infections, and thus drug interactions would not be of concern. However, in treatment of systemic infections, caution is advised with co-administration of enzyme-inducing agents because of the potential for subtherapeutic drug levels.

What They’re Good For

Single-dose therapy of most intestinal nematode infections, as an alternative for treatment of Strongyloides infection, and as treatment for tissue-invasive Echinococcus or Taenia infection.

Don’t Forget!

For some parasitic infections, drug-induced killing of the parasite releases antigens that can cause allergic reactions. Corticosteroids are sometimes ad-ministered to mitigate this effect. Know which infections this applies to before using antiparasitic for invasive infections.

References

Gallagher ,J.C. and MacDougall ,c. (2012). Antibiotics Simplified. Second Edition. Jones & Bartlett Learning, LLC.