Why One Anti-Parasite Drug Could Help Fight COVID-19

A drug used to treat “traveler’s diarrhea" could help protect human cells from coronaviruses, including SARS-CoV-2. Here’s how.

lab scientists

Medically reviewed in July 2020

Updated on July 29, 2020

Scientists across the globe are working furiously to produce a safe and effective vaccine that will protect against COVID-19. There are at least 165 experimental vaccines in various stages of development around the world. Of these, a handful are in late-stage trials, inching toward the finish line as they’re being tested among larger populations.

But what if there was another way to prevent COVID-19 from developing in the first place? While many researchers are focused on finding a vaccine, others are exploring the possibility that certain existing drugs—when used alone or in combination—could prevent infection with SARS-CoV-2, the coronavirus that causes the disease.

One of the drugs under investigation: the anti-parasite medication nitazoxanide.

An unlikely candidate
Nitazoxanide is mainly used to treat a nasty form of “traveler’s diarrhea” that’s caused by microscopic parasites. This intestinal misery results from infection with Giardia or Cryptosporidium (Crypto), which can lurk in soil, lakes and streams. These and other damp places could be contaminated by the poop (feces) of infected people or animals.

The anti-parasitic drug is generally known to be safe. The most commonly reported side effects include nausea, stomach pain, headache and discolored urine.

Signs of antiviral activity
There is evidence of nitazoxanide’s effectiveness against several viral respiratory infections, including rhinoviruses, parainfluenza viruses, RSV and the flu.

One July 2014 study published in The Lancet Infectious Diseases involving 624 otherwise healthy adults and teens diagnosed with the flu found that treatment with nitazoxanide (600 milligrams twice daily for 5 days) eased their symptoms, helping them recover about one day sooner.

In lab tests, this anti-diarrhea drug also showed antiviral activity against coronaviruses, including SARS-CoV-2. Although there currently aren’t any published findings about its safety or effectiveness as a treatment for COVID-19, there are studies underway.

How the drug could help
Generally speaking, the antiviral activity of nitazoxanide could be due to how it interferes with the pathways in human cells that parasites hijack in order to thrive.

Unlike parasites, which are single-celled organisms, viruses are essentially DNA or RNA wrapped in protein. But there is one thing that parasites and viruses have in common: They need a host to replicate.

Scientists theorize that nitazoxanide could help ramp up the cellular defenses that interfere with the ability of certain viruses, including SARS-CoV-2, to make new copies of themselves within a host cell.

Research in progress
Romark, a pharmaceutical company based in Tampa, Florida, has been investigating the antiviral possibilities of nitazoxanide for nearly a decade. The company is currently conducting two different studies on the use of nitazoxanide for the prevention of COVID-19 and other viral respiratory illnesses among two high-risk groups—older people living in long-term care facilities and frontline healthcare workers.

“Prevention is an important strategy in controlling infectious diseases and could be especially important in the context of the ongoing COVID-19 pandemic,” said Romark’s chief medical and scientific officer, Jean-François Rossignol, MD, PhD, in an April 27 news release.

Romark plans to conduct a third clinical trial exploring the use nitazoxanide for the early treatment of COVID-19 and other viral respiratory illnesses.

Scientists have also theorized that the combination of nitazoxanide and the antibiotic azithromycin could be potentially effective against COVID-19. Azithromycin is used to cover the possibility of a second infection, or superinfection, but the drug could also have some antiviral effects as well.

Much more research, however, is needed to determine if nitazoxanide is safe or effective for the prevention or treatment of COVID-19.

Article sources open article sources

The New York Times. “Coronavirus Vaccine Tracker.” July 2020.
University of Michigan Medicine. “Nitazoxanide.” 2017.
Centers for Disease Control and Prevention. “Parasites – Giardia.” July 2015.
Centers for Disease Control and Prevention. “Cryptosporidium (Crypto) and Drinking Water from Private Wells.” July 2015.
Haffizulla J, Hartman A, Hoppers M, et al. "Effect of nitazoxanide in adults and adolescents with acute uncomplicated influenza: a double-blind, randomised, placebo-controlled, phase 2b/3 trial." The Lancet Infectious Diseases. 2014.
Şimşek Yavuz S, Ünal S. "Antiviral treatment of COVID-19." Turkish Journal of Medical Sciences. 2020.
Microbiology Society. “ARE VIRUSES ALIVE?”
American Society of Health-System Pharmacists. “Assessment of Evidence for COVID-19-Related Treatments.” July 2020.
Kelleni MT. "Nitazoxanide/azithromycin combination for COVID-19: A suggested new protocol for early management." Pharmacological Research. 2020.

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