The Evidence For Ivermectin And COVID-19
Ivermectin on World Health Organization’s List of Essential Medicines
Ivermectin is a medication used to treat parasite infestations. In humans, these include head lice, scabies, river blindness (onchocerciasis), strongyloidiasis, trichuriasis, ascariasis, and lymphatic filariasis. In veterinary medicine, it is used to prevent and treat heartworm and acariasis, among other indications. It can be taken by mouth or applied to the skin for external infestations. It belongs to the avermectin family of medications. It works through many mechanisms of action that result in death of the targeted parasites.
Ivermectin was discovered in 1975 and came into medical use in 1981. In 2015, William Campbell and Satoshi Ōmura won the Nobel Prize in Physiology or Medicine for its discovery and applications. It is on the World Health Organization’s List of Essential Medicines. Ivermectin 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 one hundred thousand prescriptions. The medication is also being researched as a way to treat or prevent tropical diseases including yellow fever and malaria.
The avermectin family of compounds was discovered by Satoshi Ōmura of Kitasato University and William Campbell of Merck. In 1970, Ōmura isolated unusual Streptomyces bacteria from the soil near a golf course along the south east coast of Honshu, Japan. Ōmura sent the bacteria to William Campbell, who showed that the bacterial culture could cure mice infected with the roundworm Heligmosomoides polygyrus. Campbell isolated the active compounds from the bacterial culture, naming them “avermectins” and the bacterium Streptomyces avermitilis for the compounds’ ability to clear mice of worms (in Latin: a ‘without’, vermis ‘worms’). Of the various avermectins, Campbell’s group found the compound “avermectin B1” to be the most potent when taken orally. They synthesized modified forms of avermectin B1 to improve its pharmaceutical properties, eventually choosing a mixture of at least 80% 22,23-dihydroavermectin B1a and up to 20% 22,23-dihydroavermectin B1b, a combination they called “ivermectin”.
Merck began marketing ivermectin as a veterinary antiparasitic in 1981. By 1986, ivermectin was registered for use in 46 countries and was administered massively to cattle, sheep and other animals. By the late 1980s, ivermectin was the bestselling veterinary medicine in the world. Following its blockbuster success as a veterinary antiparasitic, another Merck scientist, Mohamed Aziz, collaborated with the World Health Organization to test the safety and efficacy of ivermectin against onchocerciasis in humans. They found it to be safe and effective, triggering Merck to register ivermectin for human use as “Mectizan” in France in 1987. A year later, Merck CEO Roy Vagelos agreed that Merck would donate all ivermectin needed to eradicate river blindness. In 1998, that donation would be expanded to include ivermectin used to treat lymphatic filariasis.
Ivermectin earned the title of “wonder drug” for the treatment of nematodes and arthropod parasites. Ivermectin has been used safely by hundreds of millions of people to treat river blindness and lymphatic filariasis.
Half of the 2015 Nobel Prize in Physiology or Medicine was awarded jointly to Campbell and Ōmura for discovering avermectin, “the derivatives of which have radically lowered the incidence of river blindness and lymphatic filariasis, as well as showing efficacy against an expanding number of other parasitic diseases”