Ivermectin: The latest Covid-19 drug candidate may be familiar to your dog

Some scientists searching for a drug to treat Covid-19 hope it might be found at the back of the medicine cabinet. If we can find a drug that already exists to treat a new disease, it could give our fight against the virus a huge second wind as we await a vaccine.

The latest drug being looked into is one you likely have only heard of if you've had lice — or know a dog.

Ivermectin was first discovered in the 1970s in soil from a Japanese golf course. Today, it treats parasitic infections like roundworms, or, in some cases head lice in people. It's also used as a dog medicine to prevent heartworm, in tablets like Heartgard.

Now, scientists are starting to look into it as a possible Covid-19 treatment.

Research supporting its usage is preliminary but compelling to scientists. In a cell culture study published in the April 2020 edition of Antiviral Research, scientists at Monash University in Australia found, within two days, a single treatment of ivermectin created a 5000-fold decrease in viral RNA. This suggests that ivermectin could prevent SARS-CoV-2 from replicating.

Preliminary research suggests these positive effects may be seen in humans too. In an observational study, scientists found that when 52 Covid-19 patients on ventilators took ivermectin, 7.7 percent died. By comparison, 18.6 percent of patients who did not receive the treatment died. Crucially this study, uploaded this week, can't determine cause-and-effect and is not peer-reviewed.

But since this study was released, interest in the drug has spiked on Google, on Youtube, and Twitter. There are also anecdotal reports of doctors using the drug to treat patients.

Despite the interest, there are reasons to hit pause on the excitement around this drug. On Twitter, Monash University has warned that the drug should not be used to treat Covid-19 in humans after the university received "a number of inquiries" about their study in cells.

How promising is ivermectin really? — As compelling as these studies are, they don't tell us much about effective the drug is. One was based only on cells outside the body. The one that evaluated humans can't totally rule out other differences in treatment (other than ivermectin) that may have accounted for the differing death rates.

There are still no published randomized, controlled clinical trials testing this drug's effectiveness in treating Covid-19. Instead, there is potential — and potential can only take you so far, Andre Kalil, a professor of internal medicine at the University of Nebraska previously told Inverse.

"This is a hard moment," Kalil said. "There are all kinds of promising news about drugs that haven’t even been tested in real trials."

The only way to know whether a drug is really promising is to test it in randomized controlled clinical trials. There currently are two trials registered with clinicaltrials.gov, that intend to look into the ivermectin's effect on humans.

We may know more in the future, but for now, ivermectin is still a few steps behind other drugs being tested against SARS-CoV-2. Human trials are already underway for remdesivir, a drug that was tested as an Ebola treatment (in that case, it wasn't as effective as scientists hoped).

There are also human trials happening for hydroxychloroquine, a drug that was catapulted to fame thanks to President Trump's endorsement and social media hype. However, as the science on the drug has progressed, we've learned that early-stage results don't always hold up.

Some studies suggest that hydroxychloroquine can lessen Covid-19 symptoms. However, a study published on March 20 that first sparked interest in the drug has been called into question by the journal that originally published it. The CDC has also removed dosing suggestions for the drug from its online treatment guidelines.

If we learned anything from the saga of hydroxychloroquine, it's that we need to take into account the side effects of drugs and study them before people start trying to use them to protect themselves from coronavirus. For instance, Nigerian officials have reported 3 cases of hydroxychloroquine poisoning since the drug gained fame.

As for ivermectin, the FDA has already expressed concern that people may do the same. In a letter released last week, the agency wrote it was "concerned about the health of consumers who may self-medicate by taking ivermectin products intended for animals."

Put bluntly, people should not take the drug, even if they already have it on hand for their pets.

Still, there's no reason we shouldn't look into drugs that show promise in cell culture. Scientists are already doing that with drugs like EIDD-2801, a drug candidate identified in a Science Translational Medicine paper that describes both a mouse study and cell experiments. That drug recently received the green-light to enter clinical trials in humans. Since these trials have yet to begin, we may not see results for a few months.

The good news is that since ivermectin is already available around the world, we may know how it works in trials fairly quickly. And once those results come in, we'll know just how promising it really is.