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Thiabendazole is an antihelmintic drug, a type of pharmaceutical used to treat worm infections in humans and livestock.[1] It is also used as a pesticide.[2] Thiabendazole is sold under the brand name Mintezol.

Use in Humans

Why It's Prescribed

For humans, thiabendazole is prescribed to treat creeping eruption (cutaneous larva migrans), pork worms (trichinosis), threadworms (strongyloidiasis), and visceral larva migrans (toxocariasis).[3] Off-label uses include Capillariasis, Dracunculiasis, and Trichostrongyliasis.

Dose, Route, and Form

Thiabendazole is available as a chewable tablet or a suspension (liquid) to be taken orally.[4]


Side Effects

Some patients who take thiabendazole may experience side effects. These include the following.[5]

More common side effects:

  • Confusion
  • Diarrhea (severe)
  • Hallucinations (seeing, hearing, and feeling things that are not there)
  • Irritability
  • Loss of appetite
  • Nausea and vomiting (severe)
  • Numbness or tingling in the hands or feet

Less common side effects:

  • Skin rash or itching

Rare side effects:

  • Aching of joints and muscles
  • Blurred or yellow vision
  • Chills
  • Convulsions (seizures)
  • Dark urine
  • Fever
  • Lower back pain
  • Pain or burning while urinating
  • Pale stools
  • Redness, blistering, peeling, or loosening of skin
  • Unusual feeling in the eyes
  • Unusual tiredness or weakness
  • Yellow eyes and skin

Patients with kidney and/or liver disease may have an increased risk of side effects.[6]

Use in Animals

Thiabendazole is used in animals, including horses, sheep, goats, cattle, swine, pheasants, cats, and dogs.[7] It is available over the counter. Individual drugs approved in the U.S. for animals are listed below, by manufacturer, including the New Animal Drug Application (NADA) number of each.

  • Merial Ltd.: Thibenzole Sheep & Goat Wormer (013-022); Equizole® Horse Wormer (013-407); Thibenzole 20% Swine Premix (013-954); Omnizole (014-350); TBZ® Cattle Wormer (Drench) (015-123); TBZ 200 Medicated Feed Premix, Thibenzole - 100, Thibenzole - 200, and Thibenzole - 45 (015-875); Thibenzole (18 mg) (030-103); Equizole® (034-114); Thibenzole Pig Wormer (035-631); Equizole® A (037-410); Tresaderm Dermatologic Solution (042-633); Thibenzole 300 Medicated (043-141); Equizole® Horse Wormer Pellets (044-654); Equizole® A Liquid (047-333); TBZ® Wormer Paste 50% (048-487); TBZ® Wormer Paste 43% (049-461); Equizole® 50% Wormer Paste and Equizole® 50% Wormer Paste For Horses (098-689)

As a Pesticide

As a pesticide, thiabendazole is used as a fungicide.[8] It is thought to be a carcinogen and a developmental/reproductive toxin with slight acute toxicity. Exposure may result in the following: dizziness, nausea, vomiting, diarrhea, epigastric distress, lethargy, fever, flushing, chills, rash, local edema, headache, tinnitus, paresthesia, hypotension, and liver injury. In California in 2008, thiabendazole was mostly used on oranges, mushrooms, and citrus crops (particularly lemons), but it was also used on landscaping, potatoes, greenhouse plants, pears, celery, and apples, and as a commodity fumigant and for "structural pest control."[9]

As a Pollutant

Because humans and animals often do not fully metabolize pharmaceuticals in their body, they can excrete drugs or their breakdown products, which may the enter the environment.[10]

In Sewage Sludge

Thiabendazole has been found in sewage sludge. In the Targeted National Sewage Sludge Survey, a 2009 test of 84 samples of sewage sludge from around the U.S., the EPA found thiabendazole in 58 samples (69%) in concentrations ranging from 8.42 to 239 parts per billion.[11] There are no federal regulations governing how much of this drug may be present in sewage sludge applied to land as fertilizer.

Articles and resources

Related SourceWatch articles


  1. Thiabendazole (Oral Route), Mayo Clinic, Accessed August 31, 2010.
  2. Thiabendazole, PAN Pesticide Database, Accessed August 31, 2010.
  3. Thiabendazole (Oral Route), Mayo Clinic, Accessed September 23, 2010.
  4. Thiabendazole (Oral Route), Mayo Clinic, Accessed September 23, 2010.
  5. Thiabendazole (Oral Route) Side Effects, Mayo Clinic, Accessed September 23, 2010.
  6. Thiabendazole (Oral Route) Before Using, Mayo Clinic, Accessed September 23, 2010.
  7. Animal Drugs @ FDA, FDA, Accessed September 23, 2010.
  8. Thiabendazole - toxicity, ecological toxicity, and regulatory information, Pesticide Action Network, Accessed September 23, 2010.
  9. Thiabendazole Use, Pesticide Action Network, Accessed September 23, 2010.
  10. O.A.H. Jones, N. Voulvoulis, and J.N. Lester, Human Pharmaceuticals in Wastewater Treatment Processes, Environmental Science and Technology, 2005.
  11. Targeted National Sewage Sludge Survey Report, US EPA website, Accessed August 28, 2010.

External resources

External articles