THIABENDAZOLE

Fetal Risk Summary

Thiabendazole is an anthelmintic agent. Reproduction studies in mice, rats, and rabbits at doses up to 2.5, 1, and 15 times, respectively, the usual human dose have revealed no evidence of fetal harm (1). When thiabendazole was prepared in an aqueous suspension, no defects were observed in mice given a dose 10 times the usual human dose. When the drug was suspended in olive oil at the same dose, however, cleft palate and axial skeletal defects were seen in mice offspring (1).

No reports of human teratogenicity caused by thiabendazole have been located. No adverse fetal effects were encountered when a single or divided dose of 50 mg/kg body weight was given to a group of pregnant women with intestinal parasites, although maternal side effects such as nausea and vomiting were common (2). The period of gestation was not specified in this report except that many of the pregnant patients received the drug just before delivery.

A 1985 review of intestinal parasites and pregnancy concluded that treatment of the pregnant patient should only be considered if the “parasite is causing clinical disease or may cause public health problems” (3). That review, and a similar article published in 1986 (4), recommended thiabendazole, when indicated, for the treatment of Strongyloides stercoralis infection occurring during pregnancy.

Breast Feeding Summary

No reports describing the use of thiabendazole during lactation have been located. The molecular weight (about 201) is low enough, however, that excretion into breast milk should be expected.

References

1. Product information. Mintezol. Merck, 2000.
2. Chari MV, Hiremath RS. Thiabendazole (a new broadspectrum anthelmintic) in intestinal helminthiasis. J Assoc Phys India 1967;15:93–6.
3. D'Alauro F, Lee RV, Pao-In K, Khairallah M. Intestinal parasites and pregnancy. Obstet Gynecol 1985;66:639–43.
4. Ellis CJ. Antiparasitic agents in pregnancy. Clin Obstet Gynecol 1986;13:269–75.