The preliminary results of several studies may show potential for the effectiveness of ivermectin as an antiviral in the treatment and prevention of COVID-19. However, it is too early to draw overarching conclusions. Clinical trials and further research are still necessary to determine whether the drug is both safe and effective in human patients infected by SARS-CoV-2.
Ivermectin, an anti-parasitic drug used as the primary ingredient in canine heartworm preventatives, was touted as a “new tool” in the “arsenal” against SARS-CoV-2, the coronavirus strain responsible for the 2020 COVID-19 pandemic. Media publications like far-right cable channel OAN touted the drug as a “cure” that could kill the virus in “just 48 hours.”
Our analysis determined that this claim is a mixture of half-truths combined with misleading and overzealous claims.
Such claims began circulating online in April 2020 when Australian researchers with the Monash Biomedicine Discovery Institute and the Peter Doherty Institute of Infection and Immunity shared findings from an in vitro study that was in preprint and had not yet been peer reviewed by the scientific community. Similar claims made headway again in June, when the research was published in the scientific journal Antiviral Research, concluding that the FDA-approved drug ivermectin — which is most commonly used to treat internal and external animal parasites — was found to effectively stop SARS-CoV-2 virus from replicating in cells cultured in petri dishes. An in vitro study differs from an in vivo study in that the research occurs inside of extracted or grown cells cultured in a lab setting rather than in vivo, whereby the research takes place within a plant, human or animal. In vitro studies typically occur in the very early stages of research as a way to test pharmaceutical drugs or interventions before moving on to living organisms.
However, there is currently little evidence to suggest that ivermectin can “cure” COVID-19 in humans. That’s because throughout the course of the study, the drug was not given to people or animals, and the findings can only provide a potential path of future study into the safety and effectiveness of the drug.
In a separate study published in July 2020 in the Journal of Bangladesh College of Physicians and Surgeons, researchers described treating 100 patients in Bangladesh who tested positive for COVID-19 — an admittedly small sample size — with a combination treatment of ivermectin and doxycycline, along with “supportive treatment.” Nearly three-quarters of the patients were considered to have a “mild” case of the disease while one-in-ten were classified as “moderate,” which begs the question of whether the test subjects improved on their own accord or if it was some form of the various treatments given.
“It is too early in this pandemic to claim major successes of the effectivity of our combination therapy (Ivermectin and Doxycycline) as our number is small and there is no control group,” concluded the study authors. "Nevertheless, the results encourage us to continue the clinical study for people of the world in this improbable crisis as each and every life counts.”
There are studies underway to further determine whether ivermectin may be used in future human trials, though they have neither been peer-reviewed nor published in a reputable journal at the time of writing.
One such study is a U.S. clinical trial that took place between May 31 and July 27, 2020, in which researchers administered a preventative treatment of ivermectin to more than 200 asymptomatic individuals who had come in close contact with a confirmed COVID-19 patient but were not diagnosed with the disease themselves. Patients were measured for their development of COVID-19 symptoms within 14 days and diagnosis was then confirmed via a swab test. The preliminary and small-scale study, which has not been published in a peer-reviewed medical journal, suggested that ivermectin may be used to prevent infection of COVID-19. But again, the findings require further testing and evidence before they may be applied to larger human populations.
In March 2022, more than 3,500 patients diagnosed with symptomatic SARS-CoV-2 were analyzed in Brazil. Of those, 679 patients were randomly assigned to receive ivermectin, 679 a placebo, and the rest were given another medical intervention. Publishing their findings in the peer-reviewed scientific journal The New England Journal of Medicine, researchers concluded that there "were no significant effects of ivermectin use on secondary outcomes or adverse events."
"Treatment with ivermectin did not result in a lower incidence of medical admission to a hospital due to progression of Covid-19 or of prolonged emergency department observation among outpatients with an early diagnosis of Covid-19," wrote the study authors.
Ivermectin is a key ingredient in the canine heartworm preventative Heartguard. The anti-parasitic belongs to a class of medication called anthelmintics and is commonly given to animals via an oral tablet that works by either killing the parasites or stopping them from developing, according to the U.S. National Library of Medicine. Ivermectin is approved by the FDA for human use and is mainly prescribed in its topical form as a treatment for external parasites like head lice. In some cases, ivermectin may be prescribed as an oral tablet, a medication called Stromectol, to treat some parasitic roundworm infections.
Throughout the course of the pandemic, the scientific community rushed to find potential treatments for SARS-CoV-2, a single-stranded RNA virus closely related to SARS-CoV, the coronavirus responsible for the 2003 SARS pandemic. Scientists turned to previous SARS-related research in order to find treatments that may also be effective in treating COVID-19, one of which was ivermectin.
To test whether the anti-parasitic may have a similar effect on SARS-CoV-2, scientists cultured the cells of fetal pigs — again, not humans — in petri dishes in a laboratory setting before infecting the cultured cells with the coronavirus. When ivermectin was administered, it was shown to effectively stop SARS-CoV-2 replicating in these cultured cells. Within 24 hours of infection, there was a 93% reduction in viral replication and a 99.8% reduction by 48 hours. Though results are promising and show potential for the effective use of the drug as an antiviral in COVID-19 and other diseases, there is no clinical evidence to suggest that ivermectin can inhibit the replication of SARS-CoV-2 in humans. In short, it is far too early to claim that ivermectin is an effective cure or a treatment, or that it may become one in the near future.
In April 2020, the U.S. Food and Drug Administration (FDA) announced that such studies are common in the early stages of drug development and warned against self-medication until additional testing occurs. The FDA’s Center for Veterinary Medicine (CVM) issued a public letter following the April prepublication of the paper, expressing the agency’s concern about people who may self-medicate with ivermectin intended for animals. At the time of publication, there was no emergency use authorization for ivermectin in the U.S. to prevent or treat COVID-19, a legal measure that would bypass many regulatory laws.
“This type of study is commonly used in the early stages of drug development. Ivermectin was not given to people or animals in this study," wrote CVM Director Dr. Steven Solomon. "Additional testing is needed to determine whether ivermectin might be safe or effective to prevent or treat coronavirus or COVID-19.”
Solomon also said that the “FDA is concerned people should never take animal drugs, as the FDA has only evaluated their safety and effectiveness in the particular animal species for which they are labeled. These animal drugs can cause serious harm in people. People should not take any form of ivermectin unless it has been prescribed to them by a licensed health care provider and is obtained through a legitimate source.”
The ivermectin study prompted a comprehensive review published in The Journal of Antibiotics analyzing both in vitro and in vivo studies to determine the antiviral effects of ivermectin since 1970. Ivermectin was shown to have antiviral effects on Zika, dengue, yellow fever, and West Nile virus, among others — findings that further highlight that the anti-parasitic drug “could serve as a potential candidate in the treatment of a wide range of viruses including COVID-19.” Even so, the authors warned that clinical trials are still necessary to determine whether the drug is both safe and effective in human patients infected by SARS-CoV-2.
In short, the efficacy of ivermectin in combating COVID-19 depends on further preclinical testing and, if it were to pass, then the drug must undergo a four-part series of clinical trials as required by law. As of August 2020, it was too soon to draw conclusions about the effectiveness of ivermectin as a treatment or cure for COVID-19.