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Warnings Mount Against Taking Livestock Dewormer to Prevent, Treat COVID-19

Doctors urged to watch for signs of ivermectin overdoses amid spike in prescriptions

spinner image Ivermectin, 3 mg tablet, sitting on a prescription label.
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The Food and Drug Administration (FDA) has turned to social media to again warn people against taking ivermectin, a medication used to treat heartworm in animals, as protection against developing COVID-19, saying it could endanger them.

“You are not a horse. You are not a cow. Seriously, y’all. Stop it,” the FDA tweeted, after Mississippi’s health department noted in August that more than 70 percent of recent calls to the state’s poison center came from people who ingested the drug purchased at livestock supply centers.

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On August 26 the Centers for Disease Control and Prevention (CDC) issued a health alert cautioning that “adverse effects associated with ivermectin misuse and overdose are increasing, as shown by a rise in calls to poison control centers reporting overdoses and more people experiencing adverse effects.”

The CDC noted that a recent study found that more than 88,000 prescriptions for ivermectin had been dispensed in the week ending August 13, a 24-fold increase from pre-pandemic prescriptions for the dewormer, which averaged 3,600 prescriptions per week from March 16, 2019 through March 13, 2020.

Signs of Ivermectin Overdose

  • Gastrointestinal symptoms such as nausea, vomiting, and diarrhea
  • Itching and hives
  • Dizziness
  • Headache
  • Muscle pain
  • More serious adverse reactions reported in clinical literature include loss of consciousness, confusion, hallucinations, seizures, coma, and death.

Source: CDC; state poison control centers

The FDA issued a press release in March warning against the misuse of the drug intended for livestock after receiving multiple reports of patients who have required medical support and been hospitalized after self-medicating with ivermectin.

Mississippi State epidemiologist Paul Myers, M.D., issued a health alert in August warning of the potential dire consequences of using a medication intended for livestock.

“Animal drugs are highly concentrated for large animals and can be highly toxic in humans,” he wrote. “Some of the symptoms associated with ivermectin toxicity include rash, nausea, vomiting, abdominal pain, neurologic disorders and potentially severe hepatitis requiring hospitalization.”

Poison control centers around the country — including in Utah, Texas, Oregon, Oklahoma, Missouri, Kansas, Iowa and Florida — have reported recent spikes in calls related to ivermectin.

The FDA has approved the use of ivermectin tablets at specific dosages to treat people with intestinal strongyloidiasis and onchocerciasis, two conditions caused by parasitic worms. The drug is also used to treat heartworm in animals, but those dosages, particularly for large animals like horses, can cause severe harm if taken by people.

The agency notes that ivermectin should not be taken without medical supervision and only for approved purposes, even at low concentrations. It also stresses that people should not take medications intended for animals.

“Even the levels of ivermectin for approved uses can interact with other medications, like blood thinners. You can also overdose on ivermectin, which can cause nausea, vomiting, diarrhea, hypotension (low blood pressure), allergic reactions (itching and hives), dizziness, ataxia (problems with balance), seizures, coma and even death,” the FDA says.

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Animal drug untested in humans as COVID-19 treatment

Early studies showed that ivermectin can inhibit the replication of the novel coronavirus, SARS-CoV-2, in cell cultures, but to achieve the same level of antiviral effectiveness in a human would require administering doses up to 100 times higher than those approved by the FDA, according to the National Institutes of Health (NIH).

So far, the NIH says there is not enough information for its panel of COVID-19 treatment experts to recommend for or against ivermectin's use as a prophylaxis.

Merck, the pharmaceutical manufacturer of Stromectol, the brand name of ivermectin, also says the medication should be used only for FDA-approved purposes. Specifically, the company said in a press statement issued in February that, it had, to date, found:

  • No scientific basis for a potential therapeutic effect against COVID-19 from preclinical studies.
  • No meaningful evidence for clinical activity or clinical efficacy in patients with COVID-19 disease.
  • A concerning lack of safety data in the majority of studies.

Ivermectin's use as a potential prophylactic has been touted by a group called the Frontline COVID-19 Critical Care Alliance, which claimed studies indicated that the medication demonstrated effectiveness in preventing COVID-19 infection before and after exposure to the coronavirus. The group, made up primarily of critical care doctors, held a press briefing on Dec. 4 in Houston calling on the NIH to recommend the drug for use against COVID-19.

Editor's note: this story has been updated to reflect new warnings about ivermectin and overdose symptoms.


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