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Is ivermectin going to kill you? Probably not unless you take the dosage meant for horses

UPDATED: Sat., Sept. 18, 2021

FILE - This Jan. 29, 2021, file photo shows the packaging and a container of veterinary ivermectin in Johannesburg, South Africa. Ivermectin, which is produced by a number of drugmakers in various countries, has been used throughout the world for decades to treat infections of parasites in humans and some large animals. Health experts and medical groups are pushing to stamp out the growing use of the drug to treat COVID-19, warning that it can cause harmful side effects and there’s little evidence it helps.  (Denis Farrell)
FILE - This Jan. 29, 2021, file photo shows the packaging and a container of veterinary ivermectin in Johannesburg, South Africa. Ivermectin, which is produced by a number of drugmakers in various countries, has been used throughout the world for decades to treat infections of parasites in humans and some large animals. Health experts and medical groups are pushing to stamp out the growing use of the drug to treat COVID-19, warning that it can cause harmful side effects and there’s little evidence it helps. (Denis Farrell)

A five-fold increase in calls to the Washington Poison Center regarding ivermectin, a medication most commonly used to deworm horses and other livestock, but recently viewed as an alternative elixir for COVID-19, has health experts worried.

It’s been a hot commodity at area feed stores, as people are turning to the animal formulation rather than the version approved for human use. Many stores contacted said they’ve seen a spike in interest in ivermectin in recent weeks.

Dr. Scott Phillips, medical director at the poison center, said there’s not enough proof that ivermectin is safe or effective as an antiviral medication for people.

The center has received 50 calls regarding ivermectin so far this year. There were 10 in all of 2020 and seven in 2019.

No ivermectin-related deaths have been reported in Washington this year.

MultiCare Deaconess Medical Center and Valley Hospital have not treated anyone for an ivermectin overdose, said Kevin Maloney, MultiCare’s media relations manager. Providence Sacred Heart Medical Center did not have information about possible ivermectin cases available.

Taking too much ivermectin can result in loss of balance, nausea, dizziness, cramping, confusion and, in extreme cases, seizures, Phillips said.

The U.S. Food and Drug Administration has approved ivermectin for human use against some skin conditions and parasites, but recently warned against its use for COVID-19. The Washington Department of Health also cautioned people against ingesting the drug as an antiviral medication.

The Washington Pharmacy Quality Assurance Commission also reminded pharmacists to use professional judgment in filling prescriptions for a drug that has yet to be proven effective against COVID-19 symptoms.

What is ivermectin?

Ivermectin went undiscovered until the 1970s when researchers from the Kitasato Institute in Tokyo, Japan stumbled across the substance in soil.

Research showed ivermectin effectively killed harmful parasites in farm-raised cattle. Farmers for years had struggled to contain destructive parasitic outbreaks in cows, so at the time ivermectin was deemed a “wonder drug” for livestock production; the discoverers of the substance earned a Nobel Prize for Physiology or Medicine in 2015 for their work.

In the 1980s, ivermectin was approved and widely distributed to other livestock, Phillips said. In 1996 it got the FDA approval for certain skin conditions and anti-parasitic uses in humans.

Now, the substance is distributed through oral tablets, cream and injectables. Humans need a prescription, but ivermectin for animals can be purchased directly at many farm supply stores.

So how did a substance meant for deworming cattle end up as a contender for COVID-19 treatment options?

During a Zika virus outbreak in 2015, Phillips said researchers found that high concentrations of ivermectin could prevent the virus from replicating and reproducing.

“That’s what led some to think that ‘Oh, this might work for other viruses,’ and that led to this sort of theory by many people that it might be beneficial,” Phillips said. “But today, we don’t have good tests that show at what dose, if at all, ivermectin might be beneficial.”

Why did the FDA say not to use it for COVID-19?

For a drug that has already been approved for human use, this cautious messaging may seem contradictory, but a Washington State University veterinary pharmacogenetics researcher said this process is typical in FDA drug approval.

When a researcher wants to know if a drug is safe and effective, they have to conduct thorough and lengthy clinical trials with hundreds, ideally thousands, of participants, said Katrina Mealey, a doctor of veterinary medicine and associate dean at the Washington State University College of Veterinary Medicine.

In a clinical trial, a control group takes the placebo and an experimental group takes the drug, Mealey said. Then researchers switch up the groups, do the experiment again, record results, and start over with a new trial group.

“For intestinal parasites, yes, (ivermectin) has gone through clinical trials for those,” Mealey said. “A drug can have FDA approval in people, but that doesn’t mean you can use it for anything. You can only use it for what the clinical trial is testing for.”

Ivermectin toxicity occurs commonly in animals, so emergency room doctors may not detect it right away in a person, Mealey said. Taking ivermectin with other drugs and at a too-high dose can also amplify the risk.

Mealey studied how ivermectin affects animals and why some dog breeds seemed to be more vulnerable to overdose.

Her research during the early 2000s led Mealey to find certain dog breeds carry a mutated gene that makes them more likely to react badly to ivermectin. She said other research done on ivermectin in humans has shown some people could carry a similar genetic predisposition, a mutated gene they may not know of before ingesting ivermectin.

“I worry that people don’t understand the risks they might be taking if they decide to start taking ivermectin, especially if they’re using animal formulations for, you know, large animals,” Mealey said. “Those formulations are very concentrated, so one, they might be getting an overdose, and two, they might be susceptible because of genetic problems.”

In horses, ivermectin doses run up to 1,200 milligrams. For humans, the recommended dose is about 3 milligrams, Phillips said.

“Ivermectin in human doses is pretty well tolerated,” Phillips said. “But when you make these dosing errors, trying to adjust from horses to people or cows to people, if you don’t do it correctly, it can result in a pretty significant overdose of these substances.”

Mealey said anyone considering ivermectin should talk to their physician.

Providers can still write prescriptions for ivermectin as a COVID medication, called “off-label” prescriptions, Phillips said.

Nationally, more than 88,000 prescriptions for ivermectin were written in August, according to data from the Centers for Disease Control and Prevention. This was 24 times the average rate.

Ryan Malcom, pharmacist at Hart and Dilatush Pharmacy in Spokane, said the pharmacy has seen an increase in calls asking about ivermectin, but they have not seen anyone come in with a written prescription for the substance. Hart and Dilatush does not stock ivermectin, he said.

“We’ve gotten a lot of calls about it but I haven’t filled one,” Malcom said. “When we tell them we don’t have it, that’s usually the end of the conversation. It sounds like they’re calling around.”

Phillips said anyone who takes ivermectin and has even mild symptoms should call the poison center to ensure they are not in danger of overdose.

The National Institute of Health started research on the possible benefits of treating COVID-19 with ivermectin, Phillips said, but these are not finished yet.

Until those results are tested and verified, Phillips said people and health care providers should wait for scientific proof before they resort to ivermectin as a treatment for COVID-19. No one should take horse- or cattle-sized doses, regardless of a prescription.

“We have to wait for the science to tell us that it’s safe and effective, like any other medication,” Phillips said. “When you prescribe off-label like this, you run the risk of not having those appropriate, you know, scientific studies to tell you that it’s safe and effective.”

Multiple livestock stores in the region have seen an uptick in calls for and sales of ivermectin.

At Inland Farm and Supply in Deer Park, manager Billy Van Egmond said they sold more ivermectin than normal in the last month, to the point where they have run out of supply once and are about to run out again, Van Egmond said.

“We’re even having trouble finding it from our supplier; they’re running out, too,” Van Egmond said.

Van Egmond noted that the pandemic has affected the store’s ability to restock on several products, not just ivermectin. But some customers were up front in their intentions to take ivermectin to treat COVID-19.

“We just tell them, you know it’s for animals, right, it’s not for humans,” Van Egmond said.

Phillips said he expected the popularity in ivermectin to slow soon, with something else taking its place in the public discourse.

“Initially we got calls about hydroxychloroquine as a treatment, and either information or potential exposures related to that,” he said. “And then it seemed … there was a big increase in disinfectant and hand sanitizer calls. And that was in probably the first six months to a year after COVID happened. And then in August, we really started to see the ivermectin calls pick up. So we’ve kind of seen a few waves of different topics throughout this 18-plus months COVID has been going on.”

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