“There’s just not any good evidence right now suggesting this is a good treatment for treating or preventing COVID-19,” said Randy McDonough, a pharmacist in Iowa City, Iowa…

Dr. David Boulware of the University of Minnesota says the drug’s side effects are mild at two or even three times the usual human dose. But formulations for farm animals might contain 1,000 times what’s safe for humans.

“It’s pretty easy to get into toxic levels,” said Boulware, an infectious disease specialist. “All these concentrated doses that are meant for a 2,000 pound horse can certainly get people sick or hospitalized for toxicity.”

Boulware says he prescribes the drug to patients a few times a year in the U.S. and more routinely when working in countries where intestinal parasites are common. But he and other experts have been alarmed by the explosive growth in U.S. ivermectin prescribing.