Thiabendazole

THIABENDAZOLE

Thiabendazole is an alternative to ivermectin or albendazole for the treatment of strongyloidiasis and cutaneous larva migrans.

Basic Pharmacology

Thiabendazole is a benzimidazole compound. Although it is a chelating agent that forms stable complexes with a number of metals, including iron, it does not bind calcium.

Thiabendazole is rapidly absorbed after ingestion. With a stan-dard dose, drug concentrations in plasma peak within 1–2 hours; the half-life is 1.2 hours. The drug is almost completely metabo-lized in the liver to the 5-hydroxy form; 90% is excreted in the urine in 48 hours, largely as the glucuronide or sulfonate conju-gate. Thiabendazole can also be absorbed from the skin.

The mechanism of action of thiabendazole is probably the same as that of other benzimidazoles (see above). The drug has ovicidal effects against some parasites.

Clinical Uses

The standard dosage, 25 mg/kg (maximum 1.5 g) twice daily, should be given after meals. Tablets should be chewed. For strongyloides infection, treatment is for 2 days. Cure rates are reportedly 93%. A course can be repeated in 1 week if indicated. In patients with hyperinfection syndrome, the standard dose is continued twice daily for 5–7 days. For cutaneous larva migrans, thiabendazole cream can be applied topically, or the oral drug can be given for 2 days (although albendazole is less toxic and there-fore preferred).

Adverse Reactions, Contraindications, & Cautions

Thiabendazole is much more toxic than other benzimidazoles and more toxic than ivermectin, so other agents are now preferred for most indications. Common adverse effects include dizziness, anorexia, nausea, and vomiting. Less common problems are epi-gastric pain, abdominal cramps, diarrhea, pruritus, headache, drowsiness, and neuropsychiatric symptoms. Irreversible liver failure and fatal Stevens-Johnson syndrome have been reported. 

Experience with thiabendazole is limited in children weighing less than 15 kg. The drug should not be used in pregnancy or in the presence of hepatic or renal disease.