The Centers for Disease Control and Prevention is warning against use of the drug ivermectin to treat COVID-19, after the unproven treatment was widely promoted on Fox News, prompting a surge of calls to poison control centers from people who’ve self-administered the drug. Ivermectin is most commonly used to treat parasites in horses and other large animals. There are no randomized controlled trials showing it benefits COVID patients. The Arkansas Medical Board is investigating one doctor who says he prescribed ivermectin thousands of times, including to Arkansas prisoners.