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Benznidazole Side Effects

Medically reviewed by Last updated on Apr 12, 2023.

Applies to benznidazole: oral tablets.

Side effects include:

GI effects (abdominal pain, abdominal bloating, decreased appetite, decreased weight, nausea, vomiting, diarrhea, constipation), headache, rash, urticaria, pruritus, dizziness, tremor, eosinophilia, neutropenia, myalgia, arthralgia or arthritis, elevated aminotransferase (transaminase) concentrations.

For Healthcare Professionals

Applies to benznidazole: oral tablet.


This drug was used in 55 pediatric patients (aged 6 to 12 years) and 64 pediatric patients (aged 7 to 12 years) during 2 controlled trials and 37 pediatric patients (aged 2 to 12 years) in an uncontrolled trial; each patient had chronic indeterminate Chagas disease.

In 1 controlled trial, this drug was discontinued due to at least 1 side effect in 5 of 55 patients; such side effects included abdominal pain, nausea, vomiting, rash, decreased appetite, headache, and elevated transaminases. The most commonly reported side effects in this trial were abdominal pain, rash, decreased weight, and headache.

In the uncontrolled trial, rash, leukopenia, urticaria, eosinophilia, decreased appetite, and neutropenia were reported in 6 of 19 pediatric patients (aged 2 to 6 years); such side effects were similar to those reported in the overall population of 37 patients.[Ref]


Very common (10% or more): Abdominal pain (up to 25%)

Common (1% to 10%): Nausea, vomiting, diarrhea

Postmarketing reports: Epigastric pain, dry mouth[Ref]


Extensive skin reactions (such as rash [maculopapular, pruritic macules, eczema, pustules, erythematous, generalized, allergic dermatitis, exfoliative dermatitis]) have been reported. Most cases occurred after about 10 days of therapy; most rashes resolved with discontinuation of therapy.[Ref]

Very common (10% or more): Rash (16%), urticaria (16%), skin lesions (11%)

Frequency not reported: Severe skin and soft tissue reactions, serious skin and subcutaneous disorders, extensive skin reactions (such as rash [maculopapular, pruritic macules, eczema, pustules, allergic dermatitis])

Postmarketing reports: Maculopapular cutaneous eruptions, erythematous plaques, generalized rash, erythematous rash, pruritic rash, blistering eruptions, peeling skin, exfoliative dermatitis, toxic epidermal necrolysis, acute generalized exanthematous pustulosis, erythema multiforme, drug reaction with eosinophilia and systemic symptoms (DRESS)[Ref]


Very common (10% or more): Leukopenia (16%), eosinophilia (16%), neutropenia (16%)

Frequency not reported: Hematological manifestations of bone marrow depression (such as neutropenia, thrombocytopenia, anemia, leukopenia)

Postmarketing reports: Lymphadenopathy, thrombocytopenia, granulocytopenia, agranulocytosis[Ref]


Very common (10% or more): Decreased appetite (up to 16%)

Common (1% to 10%): Anorexia[Ref]


Very common (10% or more): Decreased weight (13%)

Frequency not reported: Genotoxicity

Postmarketing reports: Fever, asthenia, fatigue, generalized edema, edema in the extremities, elevated alkaline phosphatase[Ref]

Nervous system

Common (1% to 10%): Headache, dizziness, peripheral neuropathy, tremor

Postmarketing reports: Paresthesia, hypoesthesia, headaches, convulsions, inability to concentrate, temporary amnesia, ageusia[Ref]


Cases of severe irreversible hepatotoxicity/acute liver failure, including cases with fatal outcomes with very rapid onset after start of systemic use of metronidazole (another nitroimidazole agent structurally related to this drug), have been reported in patients with Cockayne syndrome; latency from drug start to signs of liver failure has been as short as 2 days.[Ref]

Common (1% to 10%): Elevated transaminases

Postmarketing reports: Hepatitis, toxic hepatitis, elevated bilirubin

Another nitroimidazole agent structurally related to this drug:

-Postmarketing reports: Severe irreversible hepatotoxicity/acute liver failure in patients with Cockayne syndrome[Ref]


Common (1% to 10%): Arthralgia

Postmarketing reports: Myalgia, musculoskeletal pain, migratory arthritis[Ref]


Postmarketing reports: Insomnia, temporary disorientation[Ref]


Postmarketing reports: Eyelid edema[Ref]


1. Product Information. Benznidazole (benznidazole). Everett Laboratories Inc. 2017.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.