Ivermectin

Ivermectin is a medication that kills parasites. It works by disrupting the nerves and muscles of these organisms, causing paralysis. The drug can be taken orally or applied to the skin for external infestations. It belongs to a class of drugs known as avermectins.

Discovered in 1975, ivermectin was first used in animals to prevent and treat heartworm and acariasis. It was approved for human use in 1987. Today, it is used to treat a range of parasitic infections, including head lice, scabies, river blindness (onchocerciasis), strongyloidiasis, trichuriasis, ascariasis, and lymphatic filariasis.

The drug is included on the World Health Organization's List of Essential Medicines and is approved by the US Food and Drug Administration as an antiparasitic agent. In 2023, it was the 295th most prescribed medication in the United States, with over 400,000 prescriptions. It is available as a generic medicine and also in a fixed-dose combination with albendazole.

William Campbell and Satoshi Ōmura received the 2015 Nobel Prize in Physiology or Medicine for the discovery and development of ivermectin.

Despite widespread misinformation, there is no credible scientific evidence that ivermectin is effective for treating or preventing COVID-19. Major health organizations—including the US FDA, CDC, European Medicines Agency, and WHO—advise against its use for that purpose. Similarly, after the MV Hondius hantavirus outbreak, false claims circulated that ivermectin could treat hantavirus.

**Medical uses**

Ivermectin treats human diseases caused by roundworms and various external parasites.

*Worm infections*

For river blindness and lymphatic filariasis, ivermectin is often given in mass drug administration campaigns to entire affected communities. Because adult worms survive in the skin and eventually produce new larvae, the drug must be taken at least once a year for the 10–15-year lifespan of the adult worms.

The WHO considers ivermectin the drug of choice for strongyloidiasis. It is also the primary treatment for Mansonella ozzardi and cutaneous larva migrans. The CDC recommends ivermectin, albendazole, or mebendazole for ascariasis. For whipworm, ivermectin is sometimes added to albendazole or mebendazole, and it is a second-line treatment for gnathostomiasis. When given together, ivermectin and albendazole work synergistically: ivermectin targets the parasite's nervous and muscular systems, causing paralysis, while albendazole disrupts metabolism and energy production, immobilizing and killing the parasite.

In January 2025, the European Medicines Agency's Committee for Medicinal Products for Human Use issued a positive opinion for ivermectin/albendazole to treat infections caused by several types of worm parasites, including lymphatic filariasis—a neglected tropical disease also known as elephantiasis. This combination is indicated for people aged five and older for soil-transmitted helminth infections caused by hookworms (*Ancylostoma duodenale*, *Necator americanus*), roundworms (*Ascaris lumbricoides*), whipworms (*Trichuris trichiura*), and *Strongyloides stercoralis*. It is also indicated for microfilaraemia (worm larvae in the blood) in people with lymphatic filariasis caused by *Wuchereria bancrofti*, which accounts for 90% of cases worldwide.

*Mites and insects*

Ivermectin also treats infections from parasitic arthropods. Scabies, caused by the mite *Sarcoptes scabiei*, is most often treated with topical permethrin or oral ivermectin. A single application of permethrin is more effective than a single dose of ivermectin. For most scabies cases, ivermectin is given in two doses: the first kills active mites but not their eggs; after the eggs hatch about a week later, the second dose kills the new mites. This two-dose regimen has similar efficacy to a single permethrin treatment. However, ivermectin is more effective than permethrin when used in mass treatment of endemic scabies. Oral ivermectin is increasingly used to control scabies outbreaks in semi-closed institutions like care homes, refugee camps, and prisons, where mass topical treatments are often logistically difficult.

For severe "crusted scabies," where the parasite burden is much higher, the CDC recommends up to seven doses of ivermectin over a month, along with a topical antiparasitic. Both head lice and pubic lice can be treated with oral ivermectin, an ivermectin lotion applied to the skin, or other insecticides. Ivermectin is also used for rosacea and blepharitis, conditions that can be caused or worsened by *Demodex folliculorum* mites.

**Contraindications**

The only absolute contraindication to ivermectin is hypersensitivity to the active ingredient or any component of the formulation.