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Thiabendazole Side Effects

For the Consumer

Applies to thiabendazole: oral suspension, oral tablet chewable

As well as its needed effects, thiabendazole may cause unwanted side effects that require medical attention.

Severity: Major

If any of the following side effects occur while taking thiabendazole, check with your doctor immediately:

More common
  • 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
  • Skin rash or itching

Severity: Moderate

If any of the following side effects occur while taking thiabendazole, check with your doctor or nurse as soon as possible:

  • 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

Severity: Minor

Some thiabendazole side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned about them:

More common
  • Dizziness
  • drowsiness
  • dryness of eyes and mouth
  • headache
  • ringing or buzzing in the ears

This medicine may cause the urine to have an asparagus-like or other unusual odor while you are taking it and for about 24 hours after you stop taking it. This side effect does not need medical attention.

For Healthcare Professionals

Applies to thiabendazole: compounding powder, oral suspension, oral tablet chewable


Gastrointestinal side effects have commonly included nausea, vomiting, anorexia, and abdominal pain. These side effects generally only last 1 to 2 days and do not require drug discontinuation. Epigastric distress and abdominal pain have also been reported.[Ref]

Nervous system

Nervous system side effects have included drowsiness, dizziness, giddiness, headache, paresthesias, weariness, numbness, hyperirritability, convulsions, collapse, confusion, depression, floating sensation, weakness, and lack of coordination.[Ref]


Erythema multiforme (including Stevens-Johnson syndrome) and toxic epidermal necrolysis generally do not occur for several weeks after thiabendazole is discontinued. The reaction generally starts with a skin eruption which quickly progresses. Two reported cases had complete recovery after several weeks of therapy.[Ref]

Hypersensitivity adverse effects have included pruritic rash reactions, fever, facial flush, chills, conjunctival injection, angioedema, anaphylaxis, skin rashes (including perianal), erythema multiforme (including Stevens-Johnson syndrome), toxic epidermal necrolysis, and lymphadenopathy.[Ref]


Sicca complex has been frequently noted with the hepatic changes associated with thiabendazole. This clinical picture includes keratoconjunctivitis sicca and xerostomia. This also appears to be reversible in most cases without medical intervention.[Ref]

Hepatic side effects reported have included liver damage. It may manifest as jaundice, cholestasis, sicca syndrome, malaise, light-colored stools, and gastrointestinal upset. These symptoms generally do not occur for several weeks following thiabendazole therapy completion. Therapy usually consists of only supportive measures. In most cases the hepatic damage is reversible, although at least one patient has died as a result of hepatic damage. Sicca complex has also been reported.[Ref]


Ocular side effects have included abnormal sensation in eyes, xanthopsia, blurred vision, and transient disturbances in vision.


Cardiovascular side effects have included hypotension.


Metabolic side effects have included hyperglycemia.


Hematologic side effects have included transient leukopenia.


Genitourinary side effects have included hematuria, enuresis, malodor of the urine, and crystalluria.


Psychiatric side effects have included psychic alterations.


Other side effects have included tinnitus, drying of mucous membranes, and live Ascaris in the mouth and nose.


1. Grove DI "Treatment of strongyloidiasis with thiabendazole: an analysis of toxicity and effectiveness." Trans R Soc Trop Med Hyg 76 (1982): 114-8

2. Gann PH, Neva FA, Gam AA "A randomized trial of single- and two-dose ivermectin versus thiabendazole for treatment of strongyloidiasis." J Infect Dis 169 (1994): 1076-9

3. Nauenberg W, Edelman MH, Spingarn CL "Observations on the treatment of strongyloidiasis with thiabendazole in New York City." Mt Sinai J Med 37 (1970): 607-11

4. Tanowitz HB, Wittner M "Probable thiabendazole allergy after repeated administration." J Trop Med Hyg 73 (1970): 141-2

5. Rex D, Lumeng L, Eble J, Rex L "Intrahepatic cholestasis and sicca complex after thiabendazole: report of a case and review of the literature." Gastroenterology 85 (1983): 718-21

6. Fink AI, MacKay CJ, Cutler SS "Sicca complex and cholangiostatic jaundice in two members of a family probably caused by thiabendazole." Ophthalmology 86 (1979): 1892-6

7. Roy MA, Nugent FW, Aretz HT "Micronodular cirrhosis after thiabendazole." Dig Dis Sci 34 (1989): 938-41

8. Bion E, Pariente EA, Maitre F "Severe cholestasis and sicca syndrome after thiabendazole." J Hepatol 23 (1995): 762-3

9. Manivel JC, Bloomer JR, Snover DC "Progressive bile duct injury after thiabendazole administration." Gastroenterology 93 (1987): 245-9

10. Jalota R, Freston JW "Severe intrahepatic cholestasis due to thiabendazole." Am J Trop Med Hyg 23 (1974): 676-8

It is possible that some side effects of thiabendazole may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

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