Dubbed a “wonder drug” from Japan, ivermectin has been used since the 1980s to treat parasites like worms and lice. The drug has helped diminish the threat of river blindness and elephantiasis, both diseases caused by worms, around the world.
“There is a lot of experience with ivermectin in treating parasitic diseases — it is a drug that has an established safety and efficacy profile when used in this area,” said Dr. Mohanakrishnan Sathyamoorthy, a physician, professor, and the department chair of internal medicine at the TCU and University of North Texas Health Science Center School of Medicine.
But after a paper from April 2020 suggested ivermectin could inhibit the coronavirus from replicating — at least in a Petri dish — the FDA began cautioning people against taking the drug to prevent or treat COVID-19. Other regulatory bodies like the Centers for Disease Control and Prevention and the National Institutes of Health have also warned people to be wary.
“That basis in evidence has to be very high before large regulatory or advisory agencies are going to stand behind it,” Sathyamoorthy said. “Because when these agencies stand behind something, it then gives treating clinicians in any community significant guiding reassurance to say, ‘We can do this, and we can do this safely.’”
Even so, interest in the drug keeps rising. In Ohio last week, a judge reversed a previous decision to require a local hospital to give ivermectin to a patient to treat COVID-19. Google searches for “ivermectin” have skyrocketed since July.
Here’s what we know about ivermectin, and why there’s confusion about using it for COVID-19.
What is ivermectin?
Ivermectin is a drug approved by the FDA for the treatment of some parasites in people and animals. People need a prescription for ivermectin, which works by killing parasites, according to the U.S. National Library of Medicine.
The World Health Organization includes ivermectin on its Model List of Essential Medicines, a compendium of the safest, most helpful and cost-effective drugs needed for a “basic health-care system.”
If ivermectin is FDA-approved, why aren’t medical experts recommending people take it to prevent or treat COVID-19?
Ivermectin is FDA-approved for use against certain parasites — not viruses. Early studies with ivermectin in a lab setting suggest it might be useful against viruses that lead to diseases like dengue and Zika. However, clinical trials involving people have yet to report a similar benefit, according to the National Institutes of Health.
The 2020 study that suggested ivermectin could keep the SARS-CoV-2 virus from spreading was also an “in vitro” study, meaning it occurred in a lab setting with, in this case, Petri dishes. Other studies, however, offer a caveat: For ivermectin to be as helpful to a person with COVID-19 as it is in a dish, the dose would need to be up to 100 times stronger than the dose that’s approved for use in humans.
The FDA has specifically warned against people taking stronger doses of ivermectin used for large animals like cows and horses. Ivermectin overdoses can lead to seizures or death.
You are not a horse. You are not a cow. Seriously, y’all. Stop it. https://t.co/TWb75xYEY4
— U.S. FDA (@US_FDA) August 21, 2021
Other early research exists. For example, ivermectin might keep the spike protein from attaching to a person’s cells, according to studies from September 2020 and March this year. Both studies used computer models, not people, to assess the drug, so their findings serve as preliminary data.
A study here and a study there are not enough, according to Dr. Nikhil Bhayani, an infectious diseases physician advisor with Texas Health Resources. “Just because one study cites (a successful outcome), we cannot hang our hat on that,” he said.
When his patients ask about ivermectin, he points them to the FDA’s statement advising people not to take the drug for COVID-19. He follows what the regulatory bodies like the FDA and CDC recommend.
“If you are going to use ivermectin (for COVID-19), you’re going to only use that in the realm of clinical trials,” he said.
How do researchers assess drugs like ivermectin?
Before the FDA approves a drug for a specific purpose at a specific dose, the drug undergoes a series of studies to make sure it does what it’s supposed to do. The process can take years.
“It gives me a lot of comfort as a practicing clinician to experience that degree of vigor and attention to detail — it’s really incredible,” Sathyamoorthy said. “And I would assure the public that, having gone through that process personally … when the FDA puts its stamp of approval behind something, they mean business.”
Early studies assess the drug in multiple contexts before observing how it affects people. For an “in vitro” study — the Latin term for “in glass” — researchers isolate and observe the drug in controlled environments like test tubes or Petri dishes. Simultaneously, they might test the drug with digital models for “in silico” studies, referring to silicon in computers, or with animals for “in vivo” studies. These are Phase 0, or preclinical trials, Sathyamoorthy said.
“When the FDA puts its stamp of approval behind something, they mean business.”
– Dr. Mohanakrishnan Sathyamoorthy, department chair of internal medicine at the TCU and University of North Texas Health Science Center School of Medicine.
Typically, before a study publishes in a medical or scientific journal, it’s peer-reviewed. “Peer review is like having multiple teachers review that paper with a red marker and correct that paper, make suggestions, etc,” he said. The number of reviewers differs for each journal.
“This can take six, eight, 10 months of effort: of back-and-forth, of additional experimentation, preparation of new results, rewriting the paper and then sending it back to the editor who then redistributes it to the reviewers,” he said. “So you can see that’s a rigorous process.”
The drug will then move through multiple phases of clinical trials, or research that involves people. Phase 1 trials test the drug in a small group of people to determine a safe dosage of the drug, according to the FDA.
Phase 2 trials examine the drug in a larger group, sometimes hundreds of people who have the disease or condition the drug is meant to address. Phase 2 trials help determine the drug’s side effects. Phase 3, then, includes hundreds or thousands of people over one or more years to assess whether a drug works across broad populations and to monitor long-term side effects.
The National Institutes of Health reviews and maintains a list of clinical studies assessing ivermectin for people with COVID-19.
How can people better assess studies like these?
When someone comes across a study about a new drug use, “you really have to think twice,” said Teresa Wagner, an assistant professor at The University of North Texas Health Science Center.
Wagner is the clinical executive for health literacy at SaferCare Texas, an institute within the Health Science Center that focuses on safety in health care. She and her team make toolkits for people to help improve their health literacy.
She recommends people take two approaches when they hear about or read a new study: Ask questions, and ask experts. When she assesses a study, she determines where the study comes from, how it was designed, whether it was peer-reviewed and if other studies back it up.
Securing answers to these questions can be challenging for someone who doesn’t work in science. Wagner has tips.
To assess the credibility of a journal, for example, people can Google the keywords “impact factor” plus the name of the journal. An impact factor is a “level of credibility of a journal and it takes a while for a journal to establish,” she said — kind of like a credit score. The number measures how often people cite an average article in a journal in a certain year.
| Impact factor | Number of journals | Ranking (top percent of journals) |
| 10+ | 239 | 1.9% |
| 9+ | 290 | 2.4% |
| 8+ | 356 | 2.9% |
| 7+ | 447 | 3.6% |
| 6+ | 610 | 4.9% |
| 5+ | 871 | 7.1% |
| 4+ | 1,399 | 11.4% |
| 3+ | 2,575 | 21% |
| 2+ | 4,840 | 39.4% |
| 1+ | 8,757 | 71.2% |
| 0+ | 12,298 | 100% |
It’s a helpful but imperfect number, she said. A newer journal with a strong peer review process may have a low impact factor.
When people come across a study, she also recommends they read the whole thing — not just the headline. Key words like “in vitro” and “in silico” let people know a study involves preclinical research, not clinical trials.
“And that’s what we call translational science. It’s like, how do you take what you found in the lab and then translate that to humans?” she said.
If someone can’t find what they seek on their own, she recommends asking an expert.
“Call up your local university and ask to speak to an expert, or call a health sciences librarian or go to your primary care provider,” she said. “Call their office.”
Bhayani with Texas Health Resources also warns against information grabs from the internet, as well as relying on a single or small number of trials.
“What might be good for one person might not be good for the other,” he said. “Let’s try to respect what the experts say and what regulatory agencies have to say.”
What if my doctor prescribed me ivermectin for COVID-19?
Regulatory guidance doesn’t oversee patient care — people do. Those recommendations are “always bound by individual physicians’ judgment, discretion, knowledge, etc.,” Sathyamoorthy said.
It’s not uncommon for a doctor to, after assessing available evidence, decide to recommend a drug for something other than its intended use, especially for a disease “that’s difficult for us to treat,” he said.
“Physicians, historically, in our country and throughout the world are able to take their medical knowledge and apply it on a case by case basis to try to help a patient,” he said.
But they must always consider two things: safety and efficacy. At this time, the National Institutes of Health’s COVID-19 Treatment Guidelines Panel said there’s not enough evidence to “recommend either for or against” ivermectin to treat COVID-19.
Sathyamoorthy advises that, for any drug prescribed, if questions persist, patients should also seek guidance from resources like the NIH, CDC and FDA “to see what large bodies are recommending.” Or, he said, they should seek the expert opinion of an infectious disease specialist.
Wagner, with The University of North Texas Health Science Center, encourages people to ask their provider three questions: What is my problem? What do I need to do about it? Why do I need to do that?
“Find out why the provider is prescribing a medication that clearly has not been approved and/or has not been scientifically proven to abate COVID-19,” she said.
Then, she said, follow “what the CDC is directing people to do”: get vaccinated, wear masks, avoid crowds and wash hands. For people who already have COVID-19, monoclonal antibody therapy may be an option.
Alexis Allison is the health reporter at the Fort Worth Report. Her position is supported by a grant from Texas Health Resources. Contact her by email or via Twitter. At the Fort Worth Report, news decisions are made independently of our board members and financial supporters. Read more about our editorial independence policy here.
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