Ivermectin during the COVID-19 pandemic
Based on Wikipedia: Ivermectin during the COVID-19 pandemic
The Tweet That Launched a Lawsuit
"You are not a horse. You are not a cow. Seriously, y'all. Stop it."
In August 2021, the United States Food and Drug Administration posted those words on Twitter. The FDA—the federal agency responsible for ensuring the safety of everything from prescription drugs to frozen pizza—had resorted to barnyard humor. They were begging Americans to stop taking a livestock dewormer called ivermectin in hopes of treating a respiratory virus.
Three doctors who had been prescribing ivermectin to their patients sued the FDA over that tweet. They won. A federal court ruled in 2023 that the agency had overstepped its authority by posting what amounted to medical advice. The FDA eventually removed the social media posts, though it maintained that its scientific position remained unchanged: ivermectin does not work against COVID-19.
How did we get here? How did a drug designed to kill parasites in horses and humans become the subject of federal lawsuits, international conspiracy theories, and one of the strangest episodes of medical misinformation in modern history?
What Ivermectin Actually Is
Ivermectin is not snake oil. Far from it.
Discovered in the 1970s, ivermectin earned its developers the 2015 Nobel Prize in Physiology or Medicine. It revolutionized the treatment of parasitic infections in both animals and humans. For livestock, it kills roundworms, lungworms, and the larvae of parasitic flies. For people, it treats river blindness, scabies, and a parasitic infection called strongyloidiasis that affects an estimated 370 million people worldwide.
The drug works beautifully against parasites—multicellular organisms that take up residence inside their hosts and feed off them. Viruses, however, are something else entirely. A virus is not a worm living in your gut. It is a microscopic packet of genetic material that hijacks your own cells to replicate itself. Fighting a virus requires completely different biological mechanisms than killing a parasitic worm.
This distinction matters. A drug that excels at one task may be utterly useless at another.
The Laboratory Tease
The ivermectin story began reasonably enough. In 2020, with a novel coronavirus spreading across the globe and no treatments in sight, researchers scrambled to test existing drugs. Maybe something already on pharmacy shelves could help.
Early laboratory studies showed promise. Scientists found that ivermectin could inhibit the replication of SARS-CoV-2—the virus that causes COVID-19—in monkey kidney cells grown in lab dishes. The drug appeared to work by blocking something called nuclear transport, essentially preventing the virus from moving genetic material into the cell's nucleus.
Here is where the story takes a critical turn.
The concentration of ivermectin needed to achieve this antiviral effect in a laboratory dish was between 2.2 and 2.8 micromolar. To reach those levels in a living human body would require doses far higher than what has ever been approved as safe. The amount of ivermectin that kills parasites in your gut does not come close to the amount that would be needed to fight a virus in your bloodstream and lungs.
This is a common problem in drug development. Many substances can kill pathogens in a petri dish. Bleach kills viruses very effectively in laboratory conditions. That does not mean you should drink bleach. The question is always whether a drug can achieve therapeutic levels in the body without poisoning the patient.
For ivermectin and COVID-19, the math did not work out.
The Hope Factory
Despite these pharmacological realities, hope is a powerful force. Early in the pandemic, with hospitals overwhelmed and no vaccines available, both doctors and patients were desperate for anything that might help.
Small clinical trials began appearing, many from low- and middle-income countries with limited research infrastructure. Some seemed to show that ivermectin reduced COVID-19 mortality. These studies circulated widely on social media and among networks of physicians who believed mainstream medicine was overlooking a cheap, accessible treatment.
The appeal was obvious. Ivermectin was inexpensive, widely available, and had a long safety record when used as intended. If it worked against COVID-19, it could save lives in places that could not afford expensive new therapeutics or did not have access to vaccines.
Several countries took the plunge. Peru, India, Mexico, the Czech Republic, Slovakia, and the Philippines all granted some form of official approval for ivermectin as a COVID-19 treatment. Cities in Colombia and Brazil launched mass distribution campaigns. In some places, a black market developed as people sought the drug without prescriptions.
The Unraveling
Then the studies started falling apart.
In 2021, researchers began scrutinizing the clinical trials that had shown ivermectin working against COVID-19. What they found was troubling. Many studies had serious methodological problems. Others had data that could not be verified. Some appeared to be outright fraudulent.
Several high-profile papers were retracted—formally withdrawn by journals after investigation. One study from Egypt, which had been particularly influential because of its large size and dramatic results, was pulled due to suspected data falsification. These retracted papers had already been cited hundreds of times and incorporated into meta-analyses, statistical summaries that combined results from multiple studies.
When you remove fraudulent data from a meta-analysis, the remaining evidence often tells a very different story.
In February 2022, the American Journal of Therapeutics issued "expressions of concern"—a formal warning to readers—about two systematic reviews of ivermectin it had published the previous year. The journal worried that the underlying data might be unreliable enough to invalidate the papers' positive conclusions.
Meanwhile, well-designed large-scale trials were finally producing results. In October 2022, a major randomized controlled trial called ACTIV-6, conducted in the United States with rigorous methodology, delivered its verdict: ivermectin was not effective as a COVID-19 treatment.
The Veterinary Run
Long before the scientific consensus solidified, something strange was happening at feed stores across America.
People who could not get prescriptions for human ivermectin—or did not want to ask their doctors—turned to veterinary formulations. Farm supply stores began running low on horse dewormer paste. Some vendors started requiring customers to show photographs of themselves posing with their horses before completing a purchase, trying to ensure the medication was actually intended for animals.
The problem is that veterinary ivermectin is formulated for animals weighing over a thousand pounds. Dosing it for a human is not straightforward, and the inactive ingredients in veterinary preparations may not be safe for human consumption.
In August 2021, the Centers for Disease Control and Prevention issued a health alert after poison control centers reported a sharp rise in calls about ivermectin toxicity. The CDC described hospitalizations, including one person who had drunk an injectable cattle formulation.
That was the context for the FDA's infamous tweet.
The Politics of Parasites
How did a drug become politically polarized?
An analysis of prescribing data in the United States revealed something striking: areas that voted Republican saw a pronounced surge in ivermectin prescriptions during 2020, along with hydroxychloroquine, another drug touted as a COVID-19 treatment despite lacking evidence. The geographic distribution of ivermectin enthusiasm correlated with political affiliation.
This politicization fed into broader narratives. Ivermectin became a symbol in culture war battles over vaccines, government authority, and whom to trust during a crisis. For some, advocating for ivermectin was a way of pushing back against what they saw as a paternalistic medical establishment. For others, it represented dangerous rejection of scientific evidence.
As of June 2025, four American states have passed legislation to make ivermectin available over the counter without a prescription, allowing patients to bypass physicians entirely.
Following the Money
One common refrain among ivermectin advocates was that pharmaceutical companies had no incentive to study the drug because its patent had expired. Without patent protection, no company could charge premium prices, so no one would fund research.
There is a kernel of truth here. Drug development is expensive, and companies do prioritize products that can generate returns on investment. Generic drugs, by definition, face competition that limits profits.
But the ivermectin story reveals that even generic drugs can be lucrative under the right circumstances. Vitamedic Industria Farmaceutica, a Brazilian company, saw its annual ivermectin revenue jump to 85 million dollars in 2020—more than five times its previous level. Demand creates its own economics.
In the United States, investigative reporting uncovered a network of companies selling hydroxychloroquine and ivermectin that had amassed 72,000 customers who paid a combined 15 million dollars for consultations and medications. The network targeted right-wing and vaccine-hesitant groups through social media.
In Australia, a gastroenterologist named Thomas Borody announced he had discovered a "cure" for COVID-19 combining ivermectin with doxycycline and zinc. In interviews, Borody emphasized that "no one will make money from this." It later emerged that his company had filed a patent application for the drug combination.
The Information Virus
Perhaps more contagious than any coronavirus was the misinformation surrounding ivermectin.
Misleading websites appeared with elaborate graphics purporting to show meta-analyses proving ivermectin's efficacy. These sites had anonymous owners and multiple domain names redirecting to the same content. They looked scientific but lacked the methodological rigor of legitimate research synthesis.
Social media influencers amplified the message. Bret Weinstein, an American podcaster with a substantial following, took ivermectin on camera during a livestream and announced that both he and his wife had chosen not to get vaccinated. YouTube responded by demonetizing his channel.
In the United Kingdom, a retired nurse educator named John Campbell posted videos claiming that ivermectin use in Japan had caused a "miracle" decline in COVID cases. There was no evidence of widespread ivermectin use in Japan, and Japanese health authorities had not approved it for COVID-19 treatment. The claim was simply false.
False reports circulated in February 2022 that a Japanese pharmaceutical company had proven ivermectin's efficacy in a phase three clinical trial. The reports misrepresented preliminary laboratory data as conclusive clinical evidence.
The One Legitimate Use
Amid all this controversy, there is one very specific circumstance where ivermectin genuinely matters in COVID-19 care.
Remember strongyloidiasis, the parasitic infection affecting hundreds of millions of people? The parasite responsible, Strongyloides stercoralis, can live quietly in a human host for decades, causing few or no symptoms. But if that person's immune system becomes suppressed, the parasite can suddenly explode in numbers—a condition called strongyloides hyperinfection syndrome with a mortality rate as high as 90 percent.
COVID-19 treatment often involves corticosteroids, which reduce harmful inflammation but also suppress immune function. Multiple cases of fatal strongyloides hyperinfection have occurred after patients received corticosteroids for COVID pneumonia.
For this reason, the World Health Organization, the European Centre for Disease Prevention and Control, the Centers for Disease Control and Prevention, and the Public Health Agency of Canada all recommend that patients from regions where strongyloidiasis is common receive preventive treatment with ivermectin before or alongside corticosteroids.
If you were born in or lived extensively in Southeast Asia, Oceania, sub-Saharan Africa, South America, or the Caribbean, you are considered high risk. Central America, Eastern Europe, the Mediterranean, Mexico, the Middle East, North Africa, and the Indian subcontinent carry moderate risk.
In these cases, ivermectin is being used to treat a parasitic infection—exactly what it was designed for. It is not being used to treat COVID-19.
The Prison Doctor
One of the more disturbing chapters in this saga unfolded in Arkansas.
In 2020, a doctor at the Washington County Detention Center prescribed ivermectin to inmates without their knowledge or consent. The pills were distributed as "vitamins." In January 2022, twenty-two inmates filed a lawsuit.
The American Civil Liberties Union took up their case, and a settlement was eventually reached. The prison authorities paid compensation. The ACLU called the outcome "a victory for civil rights and medical ethics."
Prisoners, by definition, cannot freely leave when they disagree with their medical care. Administering experimental treatments to incarcerated people without consent echoes some of the darkest episodes in the history of medical research.
What the Authorities Actually Said
The official position of every major medical authority has been consistent.
The World Health Organization updated its guidelines in November 2023 to recommend strongly against using ivermectin for COVID-19, citing lack of evidence and absence of biological plausibility.
The European Medicines Agency advised against use outside of well-designed clinical trials. The drug is not authorized for COVID-19 treatment within the European Union.
The FDA has never approved ivermectin for treating any viral illness. The National Institutes of Health stated there was insufficient evidence to recommend for or against its use, which is scientific language for "we have no reason to think this works."
In the United Kingdom, the national COVID-19 Therapeutics Advisory Panel concluded that both the evidence and the biological plausibility were too weak to justify further investigation.
Brazil's health regulatory agency and major medical societies issued statements advising against ivermectin for COVID prevention or early treatment.
Merck, the company that originally developed ivermectin, stated in February 2021 that there was no good evidence the drug worked against COVID-19 and that attempting such use might be unsafe.
Mexico City's Withdrawn Experiment
In Mexico City, government officials distributed ivermectin widely as a COVID-19 treatment. They then published their observations as a research paper on SocArXiv, an archive for social science research.
The paper was withdrawn. The archive cited ethical concerns: the distribution program amounted to an experiment conducted on people without obtaining informed consent. Philip Cohen, a member of the archive's steering committee, said the article was "of very poor quality or deliberately false and misleading" and that removing it was necessary to prevent public harm.
The Aftermath
The ivermectin episode reveals how medical misinformation spreads, mutates, and persists even after being thoroughly debunked.
Some early studies were genuine attempts to find treatments amid a crisis. Others were poorly designed. A few appear to have been fraudulent. The fraudulent ones, ironically, often showed the most dramatic positive results—which made them the most widely shared.
Once misinformation takes root, retracting studies and publishing contradictory evidence does little to change minds. The original claims continue circulating long after being discredited. People remember the dramatic headline about a miracle cure. They do not remember the quiet retraction notice published months later.
For some, ivermectin became more than a drug. It became a symbol of resistance against perceived establishment overreach. That symbolism proved more durable than any clinical trial could overcome.
The conspiracy theories eventually expanded beyond COVID-19. Some proponents began claiming that ivermectin could treat all diseases, a claim so extraordinary it requires no detailed rebuttal.
Lessons from a Pandemic
The ivermectin saga offers several uncomfortable lessons.
First, laboratory results do not automatically translate to clinical effectiveness. A drug that shows promise in cell cultures may fail completely in human bodies. The dose that works in a dish may be toxic in a patient.
Second, small, poorly designed studies can produce misleading results. When dozens of low-quality studies are combined in meta-analyses, the illusion of robust evidence can emerge from a foundation of methodological sand.
Third, scientific fraud exists, and it can have real-world consequences. Fabricated data spreads faster than corrections. By the time fraud is discovered, the false conclusions may have shaped policy decisions and personal choices.
Fourth, desperation makes people vulnerable to false hope. When faced with a deadly pandemic and no good options, both patients and physicians may grasp at anything that offers promise, even if that promise is based on flimsy evidence.
Fifth, public health communication is harder than it looks. The FDA's tweet was memorable, but it also drew a lawsuit and may have reinforced distrust among those it was trying to reach. Mockery is emotionally satisfying but strategically questionable.
Finally, medicine and politics have become entangled in ways that harm both. When which drug you take becomes a statement of political identity, evidence-based treatment becomes nearly impossible.
Ivermectin remains an important medication—for treating parasites. For COVID-19, after years of research and debate, the verdict is clear. The drug does not work for that purpose, regardless of how fervently some wish it did.