Introduction
Ivermectin, a macrocyclic lactone derived from the fermentation of Streptomyces avermitilis, has long been pivotal in the fight against parasitic infections. With its broad-spectrum efficacy and favorable safety record, it remains a mainstay in treating helminthic and ectoparasitic diseases. Today, the conversation around ivermectin in human and animal health is expanding, as scientists explore its emerging roles beyond parasitology—including antiviral, antibacterial, and even anticancer potentials. This review critically examines ivermectin’s established and evolving applications across disciplines.
Could this decades-old antiparasitic hold untapped promise for future medical breakthroughs?
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Approved Uses of Ivermectin in Humans
1. Onchocerciasis (River Blindness)
Onchocerciasis, caused by the filarial nematode Onchocerca volvulus, is transmitted through the bites of infected Simulium blackflies. The disease manifests with severe itching, dermatitis, and can progress to blindness. Ivermectin is the treatment of choice as it effectively kills the microfilariae, thereby alleviating symptoms and reducing transmission. However, it does not kill adult worms, necessitating repeated treatments over several years [1].
2. Lymphatic Filariasis
Lymphatic filariasis results from infections with Wuchereria bancrofti, Brugia malayi, or Brugia timori, leading to lymphatic dysfunction, lymphedema, and elephantiasis. Ivermectin, often co-administered with diethylcarbamazine (DEC) and albendazole, effectively reduces microfilarial density in the bloodstream, contributing to global efforts to eliminate this debilitating disease [2].
3. Strongyloidiasis
Strongyloides stercoralis is an intestinal nematode that can cause chronic infections and, in immunocompromised individuals, a potentially fatal hyperinfection syndrome. Ivermectin is the treatment of choice, demonstrating superior efficacy in eradicating the parasite compared to other anthelmintics. Follow-up stool examinations are recommended to confirm clearance of infection [3].
4. Scabies
Scabies, caused by the mite Sarcoptes scabiei, leads to intense pruritus and skin lesions. While topical treatments like permethrin are commonly used, oral ivermectin is effective, particularly in cases of crusted scabies or when topical therapy is impractical. A systematic review suggests that ivermectin is a viable alternative to permethrin, especially in institutional outbreaks [4].
Approved Uses in Veterinary Medicine
1. Livestock (Cattle, Sheep, and Goats)
Ivermectin is extensively utilized to control gastrointestinal nematodes, lungworms, lice, and mites in livestock. Its broad-spectrum activity and ease of administration contribute to improved animal health and productivity. However, careful dosing is essential to prevent resistance development [5].
2. Horses
In equine practice, ivermectin is employed to treat parasites such as large and small strongyles, pinworms, ascarids, and bots. Regular deworming protocols incorporating ivermectin help maintain optimal health in horses. However, strategic deworming practices are recommended to mitigate resistance issues [6].
3. Companion Animals (Dogs and Cats)
Ivermectin is used for heartworm prevention and to treat demodectic and sarcoptic mange in dogs and cats. However, caution is advised in certain dog breeds with known sensitivity to ivermectin due to the MDR1 gene mutation, which can lead to severe neurotoxic effects [7].
Mechanism of Action
Ivermectin binds selectively and with high affinity to glutamate-gated chloride ion channels in invertebrate nerve and muscle cells. This binding increases the permeability of the cell membrane to chloride ions, resulting in hyperpolarization, paralysis, and death of the parasite. Mammalian cells lack these glutamate-gated chloride channels, which accounts for the selective toxicity of ivermectin [8].
Toxicity and Overdose
Human Toxicity
When used appropriately, ivermectin is generally safe. However, overdoses can lead to adverse effects, including:
- Neurological Symptoms: Dizziness, ataxia, seizures, and altered mental status.
- Gastrointestinal Symptoms: Nausea, vomiting, and diarrhea.
- Severe Cases: Hypotension and respiratory depression.
Management of ivermectin overdose is primarily supportive, focusing on symptomatic relief and monitoring of vital signs [9].
Animal Toxicity
Certain dog breeds, particularly those with the MDR1 gene mutation (e.g., Collies, Australian Shepherds), are more susceptible to ivermectin toxicity. Symptoms may include:
- Neurological Signs: Lethargy, ataxia, mydriasis, tremors, and seizures.
Immediate cessation of ivermectin and supportive care are essential in managing toxicity [10].
Emerging Applications
Antiviral Activity
In vitro studies have indicated that ivermectin exhibits inhibitory effects against various viruses, including HIV-1, dengue virus, and SARS-CoV-2. The proposed mechanism involves the inhibition of importin α/β-mediated nuclear transport, which is critical for viral replication. However, clinical efficacy in viral infections remains to be fully established [11].
Anticancer Potential
Emerging research suggests that ivermectin may possess anticancer properties by inducing apoptosis and inhibiting proliferation in certain cancer cell lines. These effects are thought to be mediated through modulation of multiple signaling pathways, including WNT/β-catenin and Akt/mTOR. Further studies are necessary to elucidate its potential role in oncology [12].
Antibacterial Properties
Ivermectin has demonstrated activity against specific bacterial pathogens, potentially through inhibition of bacterial DNA gyrase and other mechanisms. While these findings are promising, more research is needed to determine the clinical relevance of ivermectin as an antibacterial agent [11].
Editor’s Comments:
I had some hesitation on publishing this article and after deliberation and discussion with other scientists, I felt this topic warranted attention and discussion. This is presented as a reference for those involved with treatment of human and animal patients as well as laypeople with a goal of aggregating literature and references. The use of ivermectin must always be done with a physician or veterinarian guiding and prescribing the medication. Self-administration of ivermectin is dangerous.
Šín, R. and Kubiska, M., 2022. Death from COVID-19 of a 57-year-old man refusing medical care and self-medicating with ivermectin. Central European Journal of Public Health, 30(4), pp.265–267.
Available at: https://pubmed.ncbi.nlm.nih.gov/36718931/ [Accessed 2 April 2025].
This article also points out that while Ivermectin is being explored as a treatment for conditions outside of parasitosis, these are currently not validated as of publication. The risk of using ivermectin to treat viral illnesses or cancer can result in toxicity, death and delay of potentially lifesaving interventions with proven and tested methods.
References
- CDC. Onchocerciasis. https://www.cdc.gov/filarial-worms/hcp/clinical-care/onchocerciasis.html
- Babu, B. V., & Satyanarayana, K. (2021). Lymphatic filariasis elimination in India. International Health, 13(Suppl 1), S60–S66. https://www.sciencedirect.com/science/article/pii/S1471492224001818
- CDC. Strongyloidiasis. https://www.cdc.gov/strongyloides/hcp/clinical-care/index.html
- Rosumeck, S. et al. (2018). Efficacy of ivermectin versus permethrin for treating scabies. J Am Acad Dermatol. https://www.jaad.org/article/S0190-9622(17)32330-7/fulltext
- University of Tennessee. Ivermectin in Veterinary Medicine. https://vetmed.tennessee.edu/ivermectin-use-in-veterinary-medicine-what-you-need-to-know/
- UC Davis Center for Equine Health. https://ceh.vetmed.ucdavis.edu/health-topics/intestinal-parasites-horses
- VCA Animal Hospitals. Ivermectin Use. https://vcahospitals.com/know-your-pet/ivermectin
- DrugBank. Ivermectin. https://go.drugbank.com/drugs/DB00602
- EMS1. Understanding Ivermectin Overdose. https://www.ems1.com/coronavirus-covid-19/articles/understanding-ivermectin-I6HFMGuIN9stMjii/
- Cornell University, Riney Canine Health Center. https://www.vet.cornell.edu/departments-centers-and-institutes/riney-canine-health-center/canine-health-information/drug-sensitivity-mdr1
- Caly, L. et al. (2020). The FDA-approved drug ivermectin inhibits the replication of SARS-CoV-2 in vitro. Antiviral Research, 178. https://www.sciencedirect.com/science/article/pii/S0166354220302011
- Tang, J., Li, X., Bai, X., Yang, Z., Yang, H., Ji, Q., Pan, Q., Wang, Z. and Wang, D., 2021. Ivermectin, a potential anticancer drug derived from an antiparasitic drug. Acta Pharmacologica Sinica, 42(3), pp.371–377. Available at: https://www.sciencedirect.com/science/article/pii/S1043661820315152 [Accessed 2 Apr. 2025].
