Parasite Drug Shows Early Promise
Against COVID-19 in Vitro

Kathleen Doheny

April 08, 2020

Editor's note: Find the latest COVID-19 news and guidance in Medscape's  Coronavirus Resource Center.

An inexpensive drug used to treat parasitic infections killed the coronavirus that causes COVID-19 in less than 48 hours in a laboratory setting, Australian researchers say.

The drug, ivermectin, has been used widely used for decades. It was introduced as a veterinary drug in the 1970s. Doctors also prescribe it to treat head lice, scabies, and other infections caused by parasites. According to a report published online in the journal Antiviral Research, the drug quickly prevented replication of SARS-CoV-2, the virus that causes COVID-19. The study has been peer-reviewed and accepted for publication, although it is not yet a "definitive" version of record.

Researchers infected cells with SARS-CoV-2, then exposed them to ivermectin. "We showed that a single dose of ivermectin could kill COVID-19 in a petri dish within 48 hours, indicating potent antiviral activity," says study co-author David Jans, PhD, a professor of biochemistry and molecular biology at Monash University in Melbourne.

Even at 24 hours, "there was a really significant reduction" in the virus, study leader Kylie Wagstaff, PhD, a senior research fellow in biochemistry and molecular biology at Monash University, said in a statement.

But experts say more testing is needed to know if it works well in people and if it’s safe to use.

"No One Should Try to Self-Medicate"

"The main way we think ivermectin works is to target a key molecule of our cells that we think helps the virus to proliferate," Jans says. "By stopping this, the virus replicates more slowly, and so our immune system has a better chance to mount the antiviral response and kill the virus." Giving this or any antiviral drug early is thought to give the body the best chance of beating infection, he says.

In other studies, the researchers say, the drug has been shown to work against dengue fever and to limit infections similar to COVID-19, such as the West Nile virus.

The drug is "safe at relatively high doses, widely available, and relatively cheap, too," Jans says. The next step is more research to find the best dose for fighting COVID-19. Then researchers can begin testing in people, he says. "It is important to stress that no one should try to self-medicate with versions of ivermectin that are for veterinary purposes or head lice." The only safe way to get ivermectin is by prescription from a doctor, he says.

U.S. Experts Weigh In

The new study "certainly piqued our interest,” says Jill Weatherhead, MD, an assistant professor of adult and pediatric infectious diseases at Baylor College of Medicine in Houston. Her clinic uses the medicine to treat intestinal parasites found in international travelers or immigrants.

The important caveat, says Weatherhead, who reviewed the study but was not involved in the research, is that it was done in a lab. But "at this point, any lead we have should be investigated," she says. "What we really need to know is, could you translate that concentration [of the drug used in the lab study] into human studies and have it be safe?"

"The results are promising," agrees Katherine Seley-Radtke, PhD, a professor of chemistry and biochemistry at the University of Maryland, Baltimore County. She holds patents on compounds that are also being studied for COVID-19.

"Ivermectin," she says, "has shown effectiveness against other viruses, despite being an anti-parasitic drug." The drug is worthy of further study, Seley-Radtke says, but she calls the findings "very preliminary."


Antiviral Research: “The FDA-approved Drug Ivermectin inhibits the replication of SARS-CoV-2 in vitro.”

Katherine Seley-Radtke, PhD, professor of chemistry and biochemistry, University of Maryland, Baltimore County.

Jill Weatherhead, MD, assistant professor of adult and pediatric infectious diseases, Baylor College of Medicine, Houston.

David Jans, PhD, professor of biochemistry and molecular biology, Monash University, Melbourne, Australia.