Investigating a 'Wonder Drug': Can Ivermectin Treat Leishmaniasis?

October 6, 2025 •

4 min read

With an estimated 1.6 million new cases occurring annually, leishmaniasis primarily affects impoverished communities in Africa, Asia, and Latin America [1.6.3]. The search for safer, more effective treatments has led scientists to ask: can ivermectin treat leishmaniasis?

Quick Summary

Ivermectin shows significant promise against the Leishmania parasite in lab and animal studies by targeting parasite mitochondria and boosting the host's immune response. However, large-scale human clinical data is still needed for definitive conclusions.

Key Points

Preclinical Promise: In vitro and animal studies show ivermectin is effective against multiple Leishmania species by targeting parasite mitochondria and boosting host immunity [1.3.6, 1.3.3].
Dual Mechanism: Ivermectin exhibits both direct leishmanicidal activity and immunomodulatory effects, promoting a protective Th1 immune response [1.2.1, 1.7.1].
Limited Human Data: While some small human studies for cutaneous leishmaniasis are positive, large-scale, randomized clinical trials are lacking to confirm efficacy and safety [1.2.3].
Standard Treatments Have Drawbacks: Current therapies for leishmaniasis can be toxic, expensive, require injections, and face growing parasite resistance [1.3.3, 1.5.5].
Investigational Status: Ivermectin is not approved by the FDA or WHO for the treatment of any form of leishmaniasis; its use for this purpose is currently experimental [1.5.1].

Understanding Leishmaniasis: A Global Health Challenge

Leishmaniasis is a group of diseases caused by protozoan parasites of the Leishmania genus, transmitted through the bites of infected female phlebotomine sand flies [1.6.4]. Affecting millions globally, the disease manifests in several forms [1.6.5]:

Cutaneous Leishmaniasis (CL): The most common form, causing skin lesions and ulcers that can lead to significant scarring and disability [1.6.1].
Visceral Leishmaniasis (VL): The most severe form, also known as kala-azar. It is fatal in over 90% of cases if left untreated, as it attacks internal organs like the spleen and liver [1.6.1].
Mucocutaneous Leishmaniasis (ML): Leads to the partial or total destruction of mucous membranes of the nose, mouth, and throat [1.6.7].

Current treatments, such as pentavalent antimonials (sodium stibogluconate), amphotericin B, and miltefosine, are the cornerstones of therapy [1.5.1]. However, these treatments can be expensive, require long administration courses (often intravenous), and are associated with significant toxicity and growing parasite resistance [1.3.3, 1.5.5]. This has fueled an urgent search for safer, cheaper, and more accessible alternatives, leading researchers to investigate existing drugs for new purposes—a strategy known as drug repositioning [1.2.1].

What is Ivermectin?

Ivermectin is a broad-spectrum antiparasitic agent derived from the bacterium Streptomyces avermitilis [1.4.3]. Since the 1980s, it has been a transformative medicine in both veterinary and human health, primarily used to treat onchocerciasis (river blindness), strongyloidiasis, and other nematode infections [1.4.3]. Its established safety profile and widespread use have made it an attractive candidate for drug repositioning efforts against other diseases, including leishmaniasis [1.7.1].

The Scientific Evidence for Ivermectin Against Leishmaniasis

Research into ivermectin's efficacy against Leishmania has progressed from laboratory tests to animal models, with promising results across multiple stages.

In Vitro (Laboratory) Studies

Numerous in vitro studies have demonstrated ivermectin's direct leishmanicidal activity. It has proven effective at killing the promastigote (infective stage) and amastigote (intracellular stage) forms of various Leishmania species, including L. infantum, L. amazonensis, L. donovani, and L. tropica [1.7.1, 1.7.3, 1.7.4]. The proposed mechanisms of action include:

Targeting Parasite Mitochondria: Preliminary studies suggest ivermectin disrupts the parasite's mitochondrial function, a crucial energy-producing organelle [1.3.6, 1.7.6].
Inducing Oxidative Stress: Research shows ivermectin treatment leads to rigidity in the parasite's plasma membrane due to oxidative processes, inhibiting cell growth [1.7.1].

In Vivo (Animal) Studies

Following successful lab tests, animal models have provided further evidence. In studies using BALB/c mice and hamsters infected with various Leishmania species, ivermectin treatment resulted in significant reductions in parasite load in the spleen, liver, bone marrow, and skin lesions [1.2.1, 1.2.5, 1.3.1].

Notably, these studies also highlight ivermectin's powerful immunomodulatory effects. The drug appears to shift the host's immune system towards a protective Th1-type response, characterized by increased production of IFN-γ and IL-12 [1.2.1, 1.3.2]. This response helps macrophages—the very cells the parasite hides in—to activate and kill the intracellular amastigotes [1.3.3]. In some mouse studies, subcutaneous ivermectin achieved a 100% cure rate for cutaneous leishmaniasis one month after treatment [1.3.1]. Formulations incorporating ivermectin into polymeric micelles (IVE/Mic) have shown even better therapeutic results than the drug alone [1.2.5, 1.7.6].

Human Studies and Clinical Trials

While preclinical data is strong, evidence in humans is still emerging and primarily consists of smaller studies and case reports. There is a lack of large-scale, randomized controlled trials, which are the gold standard for medical evidence.

However, some small human studies have been encouraging. One report noted that among 35 patients with cutaneous leishmaniasis treated with ivermectin for two consecutive days, all were cured without side effects [1.2.3]. Another study found that combining ivermectin with the standard drug Glucantime resulted in the most significant reduction in lesion size for cutaneous leishmaniasis [1.3.3]. Proof-of-concept trials are also underway to assess ivermectin's safety and efficacy against post-kala-azar dermal leishmaniasis (PKDL), a complication of VL [1.3.4].

Comparison of Ivermectin vs. Standard Treatments


Feature	Ivermectin (Investigational)	Pentavalent Antimonials (e.g., Sodium Stibogluconate)	Liposomal Amphotericin B (L-AmB)	Miltefosine
Route	Oral (primarily) [1.4.3]	Intravenous (IV) or Intramuscular (IM) [1.5.1]	Intravenous (IV) [1.5.1]	Oral [1.5.1]
Mechanism	Disrupts parasite mitochondria; immunomodulation (Th1 response) [1.3.6, 1.3.3]	Inhibition of parasitic enzymes in glycolysis and fatty acid oxidation.	Binds to ergosterol in the parasite cell membrane, forming pores and causing leakage.	Disrupts cell membrane synthesis and signaling pathways [1.5.5].
Efficacy	Promising in preclinical studies; high cure rates in some small human CL studies [1.2.3, 1.3.1]. Human VL/ML data is lacking.	Historically effective, but resistance is a major problem in some regions, like parts of India [1.5.5].	Highly effective for VL, considered a drug of choice [1.5.2, 1.5.5]. Data for CL/ML is more limited [1.5.1].	The only effective oral agent approved for all three forms (CL, ML, VL) [1.5.5]. Efficacy varies by species and region [1.5.3].
Side Effects	Generally well-tolerated at standard doses [1.4.3].	Pancreatitis, cardiotoxicity (arrhythmias), bone marrow suppression, injection site pain [1.5.3, 1.5.5].	Infusion-related reactions (fever, chills), nephrotoxicity (kidney damage), hypokalemia [1.5.3].	Gastrointestinal distress (vomiting, diarrhea), liver and kidney toxicity. Teratogenic (must not be used in pregnancy) [1.5.1].
Status	Investigational for leishmaniasis; not FDA-approved for this use.	Available via CDC in the US under an IND protocol; not commercially available [1.5.6].	FDA-approved for visceral leishmaniasis [1.5.6].	FDA-approved for specific Leishmania species [1.5.6].

Conclusion: A Promising but Unproven Therapy

The existing body of research strongly suggests that ivermectin possesses significant antileishmanial properties. Its dual action of directly targeting the parasite and beneficially modulating the host immune response makes it a compelling candidate for treatment. Its potential advantages—oral administration, low cost, and a well-established safety profile—are particularly relevant for a disease that disproportionately affects resource-limited settings.

However, it is crucial to underscore that ivermectin is not currently a standard or approved treatment for any form of leishmaniasis. The evidence, while promising, is still largely preclinical. Definitive conclusions on its efficacy, optimal dosing, and safety for leishmaniasis await the results of large-scale, rigorous human clinical trials. Until then, ivermectin remains an exciting prospect in the fight against this neglected tropical disease, potentially as a future combination therapy or an alternative in regions with high drug resistance.

For more information on leishmaniasis, consult an authoritative source: World Health Organization (WHO) - Leishmaniasis

Frequently Asked Questions

You should not self-medicate with ivermectin for leishmaniasis. It is not an approved treatment, and its use should only be considered within a formal clinical trial under medical supervision. Standard, proven therapies are available through healthcare providers [1.5.1].

Studies suggest ivermectin works in two main ways: it directly attacks the parasite by disrupting the function of its mitochondria (the cell's powerhouse) and causes oxidative stress. It also helps the host's immune system fight the infection more effectively [1.3.6, 1.4.8, 1.7.1].

The primary treatments include pentavalent antimonials, liposomal amphotericin B (administered intravenously), and miltefosine (an oral medication). The choice of drug depends on the Leishmania species, the form of the disease, and the geographic region [1.5.1, 1.5.2].

The available research focuses heavily on cutaneous leishmaniasis in animal models and small human studies. There is a significant lack of data from human clinical trials regarding ivermectin's effectiveness for visceral or mucocutaneous leishmaniasis [1.7.2].

Drug repositioning, which finds new uses for approved drugs like ivermectin, is a faster and cheaper strategy than developing a new drug from scratch. This is crucial for neglected tropical diseases that primarily affect low-income populations [1.2.1].

Some animal studies have shown that topical ivermectin is significantly less effective than systemic (e.g., subcutaneous injection) administration, possibly due to poor skin absorption and inability to reach parasites inside host cells [1.3.1].

Yes, this is a promising area of research. One study in mice showed that combining ivermectin with Glucantime (a standard antimonial drug) resulted in better wound healing for cutaneous leishmaniasis than either drug alone, suggesting a potential synergistic effect [1.3.3].