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PubMed This is a summary of 17 peer-reviewed journal articles Updated
Infectious Disease · Chagas Disease

Antiparasitic Medications: Benznidazole and Nifurtimox

At a Glance

Benznidazole and nifurtimox are most effective at clearing T. cruzi early in Chagas disease, but benznidazole did not improve major heart outcomes after established Chagas cardiomyopathy. Treatment requires close blood, liver, kidney, and nerve monitoring.

Antiparasitic medications are designed to kill the T. cruzi parasite in your body. While these drugs are highly effective when given early in the infection, they are challenging to take and may not be appropriate for everyone [1].

Deciding whether to start this treatment involves balancing the hope of clearing the parasite against a high risk of side effects.

The Two Main Medications

There are currently only two drugs established to treat Chagas disease (approval varies by country): benznidazole and nifurtimox [2].

  • Benznidazole is usually the first choice for most patients [3].
  • Nifurtimox is typically used if a patient cannot tolerate benznidazole [4].

Both medications require a lengthy course: benznidazole is commonly taken for about 60 days, while nifurtimox is commonly given for 60 to 90 days [5].

When Do These Drugs Work?

The timing of treatment is critical. These drugs are most effective during:

  • The Acute Phase: Right after infection, when cure rates are very high [1].
  • The Indeterminate Phase: When you have the infection but no heart symptoms yet. Treatment here aims to potentially prevent future heart damage, and is strongly used in pediatric cases [6].
  • Congenital Cases: Treating babies born with Chagas can almost always cure them [7].

Important: The BENEFIT Trial

A landmark study called the BENEFIT trial looked at whether benznidazole could help patients who already had established Chagas cardiomyopathy (significant heart damage) [8]. The trial found that while the drug killed the parasites in the blood, it did not improve major clinical cardiac outcomes (like preventing heart failure progression, strokes, or death) in patients with established heart damage [8].

For this reason, if you already have advanced heart disease, your doctor may recommend focusing on heart medications rather than antiparasitic drugs [9]. However, for early cardiac disease, treatment may still be considered after a specialist assessment.

Living with Side Effects

It is important to be honest: these medications are “tough.” Depending on the drug and population, adverse events are very common, and a significant percentage of patients may need to discontinue the treatment early because they feel too unwell [3][10].

Common side effects include:

  • Severe Rashes: Especially with benznidazole. This can range from itchy skin to a serious hypersensitivity reaction [11].
  • Peripheral Neuropathy: Numbness, tingling, or “pins and needles” in your hands and feet. This is a sign of nerve irritation and often requires stopping the drug [3][10].
  • Stomach Issues: Severe nausea, vomiting, loss of appetite, and weight loss [10].
  • Emotional Changes: Some patients experience mood swings, anxiety, or difficulty sleeping (insomnia), particularly with nifurtimox [3].

Urgent Note: If you experience a spreading or blistering rash, facial swelling, jaundice (dark urine), fever, or new numbness and weakness, contact your prescriber immediately before stopping or restarting your medication.

Intense Monitoring

Because these drugs can be toxic to your liver and bone marrow, you cannot just “take the pills and go.” You will need a rigorous monitoring schedule [12]:

  • Baseline Tests: Before starting, you will need blood tests to check your CBC (blood counts), liver enzymes, and kidney function [12][13].
  • Regular Check-ups: You will need periodic blood tests during the course to ensure your white blood cell counts aren’t dropping and your liver is healthy; the exact schedule depends on the drug, risk factors, and local protocol [14][15].
  • Neurological Checks: Your doctor will check for new numbness or weakness at each visit [16].

Who Requires Special Precautions?

  • Pregnant People: These medications should generally be avoided during pregnancy due to potential risks to the fetus. Reliable contraception is required during treatment [7]. Discuss breastfeeding safety with your doctor.
  • Severe Liver or Kidney Disease: These conditions require specialist risk-benefit assessment and dose adjustments because they make it harder for your body to process the drugs safely [17].
  • Severe Nerve Damage: If you already have significant neuropathy, these drugs are often avoided to prevent worsening symptoms [3].

Antiparasitic treatment is a significant commitment. By working closely with your infectious disease specialist and cardiologist, you can decide if the potential benefits outweigh the risks for your specific situation.

Common questions in this guide

What are benznidazole and nifurtimox used for in Chagas disease?
Benznidazole and nifurtimox are the two established antiparasitic medicines used to treat Chagas disease by targeting the T. cruzi parasite. Benznidazole is usually the first choice, while nifurtimox is often used when benznidazole cannot be tolerated; both require a lengthy course.
Can these medicines help if Chagas disease has already damaged my heart?
They may be considered in early cardiac disease after a specialist assessment, but the benefit is different once significant heart damage is established. In the BENEFIT trial, benznidazole cleared the parasite from the blood but did not reduce major outcomes such as worsening heart failure, stroke, or death, so advanced cases may focus on heart medicines.
How long is treatment with benznidazole or nifurtimox?
Benznidazole is commonly taken for about 60 days. Nifurtimox is commonly given for 60 to 90 days, but your clinician will determine the exact regimen based on the drug, your health, and local guidance.
What side effects require an urgent call while taking Chagas medicine?
Call your prescriber immediately if you develop a spreading or blistering rash, facial swelling, fever, dark urine or jaundice, or new numbness or weakness. Do not stop, restart, or change the medicine on your own; ask the prescriber for instructions.
What tests are needed while taking benznidazole or nifurtimox?
Before treatment, blood tests usually check your complete blood count, liver enzymes, and kidney function. Periodic blood tests and neurological checks are needed during treatment to watch for changes in blood counts, liver health, numbness, or weakness; the schedule depends on the drug, your risk factors, and local protocol.
Who needs special precautions with Chagas medicines?
These drugs are generally avoided during pregnancy, and reliable contraception is required during treatment; breastfeeding safety should be discussed with your doctor. Severe liver or kidney disease and significant pre-existing nerve damage require specialist assessment and may lead to dose changes or avoidance.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Am I in a stage of Chagas (like the indeterminate phase) where antiparasitic treatment is most likely to be helpful?
  2. 2.If I already have established heart damage, why is antiparasitic treatment not typically recommended for me?
  3. 3.What is the step-by-step plan if I develop a severe rash or numbness in my hands or feet while taking this medication?
  4. 4.How often will you be checking my blood counts and liver enzymes while I am on this treatment?
  5. 5.If I have to stop treatment early due to side effects, what does that mean for my long-term monitoring?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (17)
  1. 1

    Treatment of Chagas Disease in the United States.

    Meymandi S, Hernandez S, Park S, et al.

    Current treatment options in infectious diseases 2018; (10(3)):373-388 doi:10.1007/s40506-018-0170-z.

    PMID: 30220883
  2. 2

    An evaluation of benznidazole as a Chagas disease therapeutic.

    Caldas IS, Santos EG, Novaes RD

    Expert opinion on pharmacotherapy 2019; (20(15)):1797-1807 doi:10.1080/14656566.2019.1650915.

    PMID: 31456439
  3. 3

    Tolerance to nifurtimox and benznidazole in adult patients with chronic Chagas' disease.

    Jackson Y, Wyssa B, Chappuis F

    The Journal of antimicrobial chemotherapy 2020; (75(3)):690-696 doi:10.1093/jac/dkz473.

    PMID: 31754690
  4. 4

    Toxicity of nifurtimox as second-line treatment after benznidazole intolerance in patients with chronic Chagas disease: when available options fail.

    Crespillo-Andújar C, Chamorro-Tojeiro S, Norman F, et al.

    Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases 2018; (24(12)):1344.e1-1344.e4 doi:10.1016/j.cmi.2018.06.006.

    PMID: 29906591
  5. 5

    Efficacy and Safety of Nifurtimox in Pediatric Patients with Chagas Disease: Results at 4-Year Follow-Up in a Prospective, Historically Controlled Study (CHICO SECURE).

    Altcheh J, Sierra V, Ramirez T, et al.

    Antimicrobial agents and chemotherapy 2023; (67(4)):e0119322 doi:10.1128/aac.01193-22.

    PMID: 36975790
  6. 6

    The efficacy and safety of benznidazole in adults with seropositive indeterminate form, Trypanosoma cruzi infection: a systematic review and meta-analysis.

    Trowell JW, Mitre E, Marcus R, et al.

    BMC infectious diseases 2025; (26(1)):154 doi:10.1186/s12879-025-12231-4.

    PMID: 41436958
  7. 7

    Epidemiology and pathogenesis of maternal-fetal transmission of Trypanosoma cruzi and a case for vaccine development against congenital Chagas disease.

    Rios L, Campos EE, Menon R, et al.

    Biochimica et biophysica acta. Molecular basis of disease 2020; (1866(3)):165591 doi:10.1016/j.bbadis.2019.165591.

    PMID: 31678160
  8. 8

    Randomized Trial of Benznidazole for Chronic Chagas' Cardiomyopathy.

    Morillo CA, Marin-Neto JA, Avezum A, et al.

    The New England journal of medicine 2015; (373(14)):1295-306 doi:10.1056/NEJMoa1507574.

    PMID: 26323937
  9. 9

    Transplantation for chagas' disease: closing the knowledge gap.

    La Hoz RM

    Current opinion in infectious diseases 2022; (35(5)):397-403 doi:10.1097/QCO.0000000000000868.

    PMID: 35942849
  10. 10

    Antitrypanosomal therapy for Chagas disease: A single center experience with adverse drug reactions and strategies for enhancing treatment completion.

    Reifler K, Wheelock A, Hall SM, et al.

    PLoS neglected tropical diseases 2025; (19(7)):e0013218 doi:10.1371/journal.pntd.0013218.

    PMID: 40622934
  11. 11

    Cutaneous reactions during treatment with Nifurtimox or Benznidazole among Trypanosoma cruzi seropositive adults without symptomatic cardiomyopathy: A safety sub analysis of a placebo-controlled randomised trial.

    Villar JC, Saavedra MF, Bermúdez PA, et al.

    Tropical medicine & international health : TM & IH 2025; (30(7)):673-684 doi:10.1111/tmi.14123.

    PMID: 40384408
  12. 12

    Causality and Severity of Adverse Reactions and Biochemical Changes to Benznidazole Treatment in Patients with Chronic Chagas Disease.

    Belmino ACDC, Sousa EKS, Silva Filho JDD, et al.

    Arquivos brasileiros de cardiologia 2024; (121(8)):e20230787 doi:10.36660/abc.20230787.

    PMID: 39292117
  13. 13

    What to expect and when: benznidazole toxicity in chronic Chagas' disease treatment.

    Aldasoro E, Posada E, Requena-Méndez A, et al.

    The Journal of antimicrobial chemotherapy 2018; (73(4)):1060-1067 doi:10.1093/jac/dkx516.

    PMID: 29351667
  14. 14

    Toxic Profile of Benznidazole in Patients with Chronic Chagas Disease: Risk Factors and Comparison of the Product from Two Different Manufacturers.

    Molina I, Salvador F, Sánchez-Montalvá A, et al.

    Antimicrobial agents and chemotherapy 2015; (59(10)):6125-31 doi:10.1128/AAC.04660-14.

    PMID: 26195525
  15. 15

    Association of HLA-B∗35 and moderate or severe cutaneous reactions secondary to benznidazole treatment in chronic chagas disease.

    Bosch-Nicolau P, Salvador F, Sánchez-Montalvá A, et al.

    Clinical microbiology and infection : the official publication of the European Society of Clinical Microbiology and Infectious Diseases 2022; (28(6)):881.e1-881.e5 doi:10.1016/j.cmi.2021.11.021.

    PMID: 34863919
  16. 16

    Trypanocidal drugs for late-stage, symptomatic Chagas disease (Trypanosoma cruzi infection).

    Vallejo M, Reyes PP, Martinez Garcia M, Gonzalez Garay AG

    The Cochrane database of systematic reviews 2020; (12()):CD004102 doi:10.1002/14651858.CD004102.pub3.

    PMID: 33305846
  17. 17

    Chagas Disease in the Non-Endemic Area of Rome, Italy: Ten Years of Experience and a Brief Overview.

    Giancola ML, Angheben A, Scorzolini L, et al.

    Infectious disease reports 2024; (16(4)):650-663 doi:10.3390/idr16040050.

    PMID: 39195001

This page explains antiparasitic treatment for Chagas disease and cardiomyopathy for informational purposes only and does not constitute medical advice. Your infectious disease specialist and cardiologist can interpret your risks and monitoring needs.

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