A Nobel Prize and a horse dewormer: Explaining the controversy over ivermectin and COVID-19

To prevent or treat COVID-19, would you consider using a drug labeled "for oral use in horses only"? 

How about one whose creation, for human beings, won a Nobel Prize?

Both drugs are ivermectin. 

So perhaps it’s no wonder that debate continues to swirl about whether ivermectin, for the coronavirus, is only for crackpots or has its place in the fight against the pandemic. 

Even as prescriptions for ivermectin have risen 24-fold since before the pandemic, and some people have resorted to pressuring hospitals to use it on COVID-19 patients, public health authorities strongly recommend against using ivermectin for COVID-19. There is no conclusive evidence that it is effective, and it carries physical risks. At the same time, those dubiously touting ivermectin aren’t wrong about the Nobel Prize or the drug’s proven but limited uses for humans. 

Two widely shared Sept. 6 Facebook posts illustrate the angst among some ivermectin supporters. 

One said: "The creator of Ivermectin was awarded the 2015 Nobel Prize for its use in humans. Any journalist who refers to it as ‘horse dewormer’ is guilty of malpractice." 

The other, referring to the American Medical Association, the federal Centers for Disease Control and Prevention, and the U.S. Food and Drug Administration, claimed: "The safety profile for *prescribed* Ivermectin is excellent. And yet, the AMA, CDC, FDA etc have bastardized and restricted its use, in an effort to tout vaccination as the only prevention/treatment of COVID."

In 2015, U.S. parasite biology expert William C. Campbell and Japanese microbiologist Satoshi Omura won a Nobel Prize for their discovery of ivermectin and its use to treat diseases caused by parasites. "The importance of ivermectin for improving the health and well-being of millions of individuals with River Blindness and Lymphatic Filariasis, primarily in the poorest regions of the world, is immeasurable," the announcement of the award said.

River Blindness leads to blindness, and Lymphatic Filariasis causes chronic swelling and leads to conditions such as elephantiasis, the announcement said.

But COVID-19 is a different type of disease. COVID-19 is caused by a coronavirus, not by parasites. 

Some forms of ivermectin are used in animals to prevent heartworm disease and parasites.

In the United States, ivermectin is not approved to prevent or treat COVID-19. The FDA says in warning against using it:

"Certain animal formulations of ivermectin such as pour-on, injectable, paste, and ‘drench,’ are approved in the U.S. to treat or prevent parasites in animals. For humans, ivermectin tablets are approved at very specific doses to treat some parasitic worms, and there are topical (on the skin) formulations for head lice and skin conditions like rosacea. However, the FDA has received multiple reports of patients who have required medical attention, including hospitalization, after self-medicating with ivermectin intended for livestock."

Some limited studies suggested that ivermectin can help treat COVID-19; others show no significant impact. Overall, many of the studies had small sample sizes and other limitations. Some researchers have called for more study of the drug.

​​In June, one meta-analysis — an analysis of results from other studies — arrived at a different conclusion than another one in June did.

One meta-analysis concluded that "moderate-certainty evidence finds that large reductions in COVID-19 deaths are possible using ivermectin." That study was done by researchers affiliated with a group that is campaigning for ivermectin to be approved for COVID-19 use. 

But the other meta-analysis found that ivermectin did not reduce death or length of hospital stay when compared to conventional treatment. The study concluded that the drug "is not a viable option to treat COVID-19 patients."

In July, researchers from Germany and the UK who examined studies on ivermectin and COVID-19 concluded:

"Based on the current very low- to low-certainty evidence, we are uncertain about the efficacy and safety of ivermectin used to treat or prevent COVID-19. 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 COVID-19 outside of well-designed randomized trials."

The World Health Organization, in its COVID-19 treatment guidelines, says: "We recommend not to use ivermectin in patients with COVID-19 except in the context of a clinical trial," citing "very low certainty evidence" about the drug.

Clinical trials assessing ivermectin tablets for the prevention or treatment of COVID-19 in people are ongoing.

RELATED: No evidence yet concluding that ivermectin is an effective COVID-19 treatment