Doctors plead for people to stop taking horse dewormer for Covid
Joe Rogan used the drug after he tested positive for Covid
Patients in Oklahoma have been needing urgent treatment after overdosing on the drug, the BBC reports.
Small doses of Ivermectin are approved for use on humans, but not for Covid, despite Rogan's endorsement.
"You've got to have a prescription for this medication for a reason - because it can be dangerous," Dr Jason McElyea told the broadcaster.
He said a "handful" of people overdosing on the drug were putting further strain on hospital staff already stretched by a surge in Covid.
"The [emergency rooms] are so backed up that gunshot victims were having hard times getting to facilities where they can get definitive care and be treated," he told local broadcaster KFOR.
Ivermectin, mainly a veterinary deworming agent, can be used in small doses to treat some human conditions.
But the drug has become controversial after being promoted as a way of treating or preventing Covid and being endorsed by people like Rogan, who has been dismissive of vaccines.
The US that the Food and Drug Administration (FDA) released a statement last month urging people not to take it.
"You are not a horse. You are not a cow," the FDA said. It added that taking large doses of the substance "is dangerous and can cause serious harm".
Dr McElyea said patients who had taken Ivermectin were suffering from vomiting, muscle aches, and even vision loss.
"Some people taking inappropriate doses have actually put themselves in worse conditions than if they'd caught Covid," he told KFOR.
"You have to ask yourself, 'If I take this medicine, what am I going to do if something bad happens?' What's your next step, what's your back-up plan? If you're going to take a medicine that could affect your health, do it with a doctor on board."