The idea that a medicine that rids livestock of parasites also might help humans with COVID-19 sounds laughable, but the Food and Drug Administration (FDA) says people are using ivermectin to treat the virus and could get very sick from it.
"Animal drugs are often highly concentrated because they are used for large animals like horses and cows, which can weigh a lot more than we do - a ton or more," an FDA agency webpage reads. "Such high doses can be highly toxic in humans."
The use of it to prevent or treat the virus - now in the highly transmissible delta surge - resulted in a five-fold increase in cases of illness related to ivermectin's toxicity in July, internal CDC documents revealed.
In Mississippi, more specifically, the state poison control center issued a warning on Friday because two-thirds of its recent calls were over human use of the livestock formula of the drug.
The FDA even tried to use a little casual humor in its weekend Twitter warning accompanying an article on the drug.
"You are not a horse," it said. "You are not a cow. Seriously, y'all. Stop it."
Tammie Jowers, store manager at Tractor Supply in Trenton, Ga., said her shelves have been "wiped clean" of the drug in both the injectible paste and pour-on forms for animals, and that she "cannot get ahold of it." She has had to give people - including "not regular customers" - rain-checks.
She said the store has signs posted that the drug is not approved for humans by the FDA, and she says customers don't ask her whether they can use it themselves. But she says she has had people "swear by it."
The problem, Jowers said, is "all about the dosage."
And, she said, "I know I do not want to eat anything that de-worms a horse."
Early in the pandemic, extremely preliminary data - based on an experiment in a petri dish, not in humans - hinted at the possibility ivermectin might help treat or prevent COVID, but follow-up studies failed to demonstrate any benefit.
The drug is otherwise approved for humans by the FDA for treatment of head lice, skin issues like rosacea and conditions stemming from parasitic worms.
But the FDA warns an overdose of the highly concentrated animal versions could result in seizures, coma and even death. Mississippi health officials said symptoms might include "rash, nausea, vomiting, abdominal pain, neurologic disorders, and potentially severe hepatitis requiring hospitalization."
The FDA first warned of the drug's off-label use for COVID-19 in April of last year, saying it "has only evaluated [its] safety and effectiveness in the particular animal species for which [it is] labeled. People should not take any form of ivermectin unless it has been prescribed to them by a licensed health care provider and is obtained through a legitimate source."
Jowers said when things were so bad last year, they removed it from shelves and put it behind the counter.
"We just wanted to help people understand," she said.
We're with the FDA, though. "Seriously, y'all. Stop it."