When is ivermectin safe for humans and other questions about anti-parasitic drug not recommended for COVID-19

An anti-parasitic medicine calledivermectinisfacing a shortagein Canada amidunproven claims that it can be used to treat COVID-19 andconfusion about the drug has sparked a lot of questions.

Developed in the 1970s, ivermectin isused to treat parasites, such as intestinal worms or lice, in animals and humans.

But early studiesexploring its effectiveness as an anti-viral medication that could be used to treat COVID-19 have beenused to fuel misinformation despite being deemed low-qualityandrobustly debunked byfederal health agencies.

WATCH | Feed shops see demand for ivermectin despite health warnings:

Feed shops see demand for ivermectin despite health warnings

3 years ago

Duration 1:58

Feed shops have seen increased demand for ivermectin, commonly used to deworm livestock, to treat or prevent COVID-19, despite health warnings that it doesnt work and isnt safe for human consumption.

"The body of evidence that we now haveis that it is not effective in the context of COVID either for preventing or for treating. The evidence simply does not support it,"Tim Caulfield, a professor andthe Canada Research Chair in health law and policy at the University of Alberta, saidMonday on CBC'sThe Homestretch.

"[But] we're seeing the popularity of the drug increase, and also, there's been an increase in poisoning and an increase in prescription.It's a really bizarre phenomenon."

So, what is ivermectin and how is it used? Can it help to treat COVID-19? And why are federal agencies like Health Canada and the U.S. Food and Drug Administration warning people not to take it?

Here are some frequently asked questions about ivermectin answered.

When isivermectinsafe for human use?

Ivermectin is safe for human use when prescribed and dosed by a health-care professional to treat parasitic infections.

Dosage is based on the patient's weight,medical conditionsand response to the drug.

The form of the drug used onhumans won theNobel Prize, has improved the health of millionsandhelped to eradicate diseases like river blindness in multiple countries.

It is on the World Health Organization's list of essential medicines because it is inexpensive and effective and has proven to be life-saving for treating some illnesses caused by parasites.

The form of ivermectin intended for humans can also pose risks.Even for approved uses, ivermectin can interact with other medication or be inappropriate for people with certain health conditions that's why it's best used with a doctor's prescription.

How is theivermectinused to treat livestock different?

Ivermectin products for veterinary use are dosed for larger animals,like horses or cows,which weigh a lot more than a person. For example, a horsecan weighbetween380 and1,000kilograms.

This means that ivermectin products for animals have a higher concentrated dose than ivermectin products for people, Health Canada says.

Some veterinary drugs may also contain different ratios of medication than the human versionsand may go through different testing.

So, what could happen if I take ivermectinimproperly?

The veterinary version of ivermectin, especially at high doses, can be dangerous for humans, Health Canada says.

It may cause serious health problems such as vomiting, diarrhea, low blood pressure, allergic reactions, dizziness, seizures, coma and even death.

"Canadians should never consume health products intended for animals because of the potential serious health dangers posed by them," Health Canada said.

In the U.S., the Centers for Disease Control warned the public after increased calls to poison centres with reports of severe illness caused by the medicine.

Last week, the U.S. Food and Drug Administration (FDA) also reissued warnings about ivermectin in response to a growing volume of misinformation on social media, along withreports of people being poisoned and requiring hospitalization after taking it.

"You are not a horse. You are not a cow. Seriously, y'all. Stop it," said a tweet from the U.S. FDA.

Can ivermectin be used to treat COVID-19?

First of all, ivermectin is used to treat parasites. COVID-19 is caused by a virus.

Some early studiesappeared to show promise for its use as an anti-viral as well as an anti-parasitic with hope that further study could prove itinhibits the growth of the novel coronavirus in human cells and improve patientoutcomes.

Those results have notpanned out in larger, higher quality studies, which have yet toprove whetherivermectincanslow or stop the novel coronavirus from growing in human cells.

After reports thatsome people weretakingthe veterinary form of the medicine intended for livestock, Health Canadaissued an advisoryon Tuesdayasking people not to take the drug to treat COVID-19.

"There is no evidence that ivermectin in either [the human or veterinary] formulation is safe or effective when used for those purposes," it said.

Health Canada saysit's closely monitoring all potential treatments for COVID-19, including ivermectin.

"Should a manufacturer provide a submission to Health Canada related to the use of ivermectin to prevent or treat COVID-19, Health Canada would conduct a scientific evaluation of the evidence to determine the drug's quality, safety and effectiveness," the agency said.

But so far, ivermectin is only approved for use to treat parasites in Canada not COVID.

A full list ofdrugs and vaccinationsauthorized for the treatment or prevention of COVID-19 is available on Health Canada's website.

But I read, or heard about, studies that suggested it was effective in treating COVID-19. What gives?

Dr. Lynora Saxinger, an infectious disease specialist at the University of Alberta, told CBC Newsthat early studies of ivermectin's use either as a COVID-19 treatment or preventionconsisted of low-quality data.

A review publishedin April in theCochrane Database of Systematic Reviewsconcluded that theefficacy and safety of ivermectinto treat or prevent COVID19 is unproven.

"The completed studies are small and few are considered high quality. Several studies are underway that may produce clearer answers in review updates. Overall, the reliable evidence available does not support the use of ivermectin for treatment or prevention of COVID19 outside of welldesigned randomized trials," it determined.

One issue was that in some initial positive reports, patients were receiving multiple medications, so the effect of ivermectin couldn't be parsed out. Another was thatextremely high doses that showed promise in test tubes didn't translate to human subjects.

Some studies or systematic reviews also consisted of small sample sizes.

WATCH |Horse medication ineffective against COVID-19, says specialist:

Horse medication ineffective against COVID-19, says specialist

3 years ago

Duration 1:10

Epidemiologist Dr. Christopher Labos says getting vaccinated is a safer and better way to protect against the coronavirus.(Benoit Tessier/Reuters)

Medical journal The Lancet has called for more study on ivermectin's efficacy to reduce SARS-CoV-2 viral load or improve recovery but said there is no drug that can replace preventative public health policies and large-scale testing for COVID.

Merck, the initial manufacturer of ivermectin, confirmeditsscientists have found no scientific basis for ivermectin's efficacy against COVID-19, also citing aconcerning lack of safety data in most studies.

And Alberta Health Services says its scientific advisory group has conducted a review to explore using ivermectin, but the drug is not approved to treat COVID-19 in the province.

It advises against taking ivermectin as a COVID-19 treatment outside of clinical trials.

So, why wasivermectinsuggested as a treatment when it's unproven?

It started in November 2020, when a study was published in Egypt suggesting ivermectincould improve outcomes for COVID-19 patients.

It was the largest study in favour of the drug but this summer itwas retractedafter concerns about data fabrication, plagiarism and ethical breaches.

Before it was retracted, it prompteddoctors in some countries to start using the drug just to see what would happen, because it'seasily available and inexpensive.

The retracted study also sparked buzz, especially with one right-wing group known for spreading medical misinformation calledAmerica's Frontline Doctors, which has been charging patients for consultations to access ivermectin.

In December 2020, Dr. Pierre Kory, who has been an outspoken advocate for ivermectin, called it a miracle drug before a U.S. Senate hearing on COVID-19 treatments. Kory has since said he regrets using that hyperbolic term.

An article on ivermectin's use in treating COVID, written by the Front Line COVID-19 Critical Care Alliance, which counts Kory among its members, was removed from the journal Frontiers in Pharmacology after editors determined it contained unsubstantiated claims and violated its editorial policies.

But all that hasn't stopped a number of politicians and media figures from toutingthe drug as a possible treatment, preventionor cure.

What's the bottom line?

Ivermectinhas not been proven to effectivelytreatCOVID-19, and it can be dangerous when taken in high doses or without the guidance of a health-care professional.