If you know someone who's taking, or thinking about taking, horse dewormer for Covid-19, pass this along to them

Cartoon by Nick Anderson

Demand is surging nationwide for ivermectin, an anti-parasitic drug typically used for livestock, based on unsubstantiated claims that it can help Covid-19 patients. How bad is it? A Las Vegas-area feed store is requiring customers to show a picture of themselves with their horse before they can buy it, and the Food and Drug Administration, the Centers for Disease Control and Prevention and the National Institutes of Health have warned against using it to treat Covid-19.

This didn't start with ivermectin. It's largely a function of trust, or lack of it: in government, in science, and in the "elites" believed to control both. When Donald Trump, whom supporters saw as an outsider, cast doubt on top scientists from the beginning of the pandemic, it set the stage for supporters to doubt them when vaccines were released. Trump also advocated for untested Covid therapeutics such as hydroxychloroquine and publicly floated the notion of injecting disinfectants into the body to "clean" the lungs. Some followers listened; hydroxychloroquine prescriptions shot up 900% in 2020, leading to shortages for patients with autoimmune disease. And the day after Trump retweeted a viral video from America's Frontline Doctors claiming hydroxychloroquine cured Covid-19, poison-control centers in many states saw a significant rise in calls from people who had ingested bleach, Lysol and other household cleaners.

Part of the appeal of HCQ and ivermectin is that both drugs have already been FDA-approved and have been long in use to fight other human diseases. Ivermectin is used to treat parasites in animals and humans, but has a long history of being promoted as a panacea for everything from AIDS to autism. Last summer it became popular in Latin America and India for Covid treatment, mostly because doctors didn't have access to a vaccine and believed an experimental treatment was better than nothing.

But the science is inconclusive at best, and leading scientific bodies have said so. The studies ivermectin fans often cite are either far too limited in scale to draw conclusions (which the studies' authors acknowledged), or say ivermectin only shows a therapeutic effect at toxic doses, or are ethically suspect. One study was yanked from a peer-reviewed journal almost immediately because the paper contained unsubstantiated claims and promoted the authors' own ivermectin treatment.

In some cases, courts have forced hospitals to allow Covid-19 patients receive ivermectin. Why not just let them take it? It's not necessarily safe, for one thing: Some people are experiencing violent diarrhea and other side effects from taking it, especially those using the over-the-counter version meant for animals. And putting one's faith in ivermectin may dissuade people from seeking other experimental but approved treatments for Covid-19, such as monoclonal antibodies.

UPDATE: Greg Sargent of The Washington Post explains "How right-wing media and social isolation lead people to eat horse paste," which tastes awful.