Ivermectin (, EYE-vər-MEK-tin) is an antiparasitic drug. After its discovery in 1975, its first uses were in veterinary medicine to prevent and treat heartworm and acariasis. Approved for human use in 1987, today it is used to treat infestations including head lice, scabies, river blindness (onchocerciasis), strongyloidiasis, trichuriasis, ascariasis and lymphatic filariasis. It works through many mechanisms to kill the targeted parasites, and can be taken orally, or applied to the skin for external infestations. It belongs to the avermectin family of medications. William Campbell and Satoshi Ōmura won the 2015 Nobel Prize in Physiology or Medicine for its discovery and applications. It is on the World Health Organization's List of Essential Medicines, and is approved by the U.S. Food and Drug Administration as an antiparasitic agent. In 2018, it was the 420th most commonly prescribed medication in the United States, with more than 100,000 prescriptions. It is available as a generic medicine. During the COVID-19 pandemic, misinformation has been widely spread claiming that ivermectin is beneficial for treating and preventing COVID-19. Such claims are not backed by credible scientific evidence. Multiple major health organizations, including the Food and Drug Administration, U.S. Centers for Disease Control, the European Medicines Agency, and the World Health Organization have stated that ivermectin is not authorized or approved to treat COVID-19. Medical uses Ivermectin is used to treat human diseases caused by roundworms and a wide variety of external parasites. Worm infections For river blindness (onchocerciasis) and lymphatic filariasis, ivermectin is typically given as part of mass drug administration campaigns that distribute the drug to all members of a community affected by the disease. For river blindness, a single oral dose of ivermectin (150 micrograms per kilogram of body weight) clears the body of larval Onchocerca volvulus worms for several months, preventing transmission and disease progression. Adult worms survive in the skin and eventually recover to produce larval worms again; to keep the worms at bay, ivermectin is given at least once per year for the 1015-year lifespan of the adult worms. For lymphatic filariasis, oral ivermectin (200 micrograms per kilogram body weight) is part of a combination treatment given annually: ivermectin, diethylcarbamazine citrate and albendazole in places without onchocerciasis; and ivermectin and albendazole in places with onchocerciasis. The World Health Organization (WHO) considers ivermectin the drug of choice for strongyloidiasis. Most cases are treated with two daily doses of oral ivermectin (200 μg