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Can Antimalarial Drugs Really Stop COVID-19? We Just Don’t Know Yet.

We’re all desperate for a solution to the novel coronavirus outbreak, and few things sound as promising as repurposing existing drugs to treat this illness. President Trump has enthusiastically touted this idea — suggesting in particular the use of chloroquine and hydroxychloroquine, two antimalarial drugs.

But safe and effective treatment of COVID-19 isn’t as simple as handing out medication currently available. Doctors can prescribe drugs to treat illnesses other than the ones they were approved for, and many may already be doing that to fight this disease. But experts say that’s a risky and unreliable way to combat the pandemic, and it may cause more harm than good.

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“People can die from these drugs, and we would never know they died from the drugs because we didn’t have controls,” said Dr. Andre Kalil, an infectious disease specialist at the University of Nebraska Medical Center.

Every medication has potential side effects, and doctors have to weigh the risks and benefits whenever they prescribe one. This is true even for something as simple as aspirin, which is often used to prevent heart attacks and strokes but also comes with side effects like an increased risk of bleeding.

“That’s why we don’t put healthy 30-year-olds on aspirin,” said Dr. Caleb Alexander, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health. “It’s not because aspirin won’t help prevent a heart attack — it will. It’s because a healthy 30-year-old has such an unlikely risk of having a heart attack that the possibility of bleeding from aspirin outweighs the benefit.”

Though medications like chloroquine and the antiviral drug remdesivir are being considered to fight COVID-19, doctors can’t do a proper risk-benefit analysis because they don’t yet know whether these drugs are actually effective in treating the infection. Experts suspect they might be because they have antiviral or anti-inflammation properties or because in vitro tests or very preliminary trials have shown positive results, but until researchers conduct full trials, we simply don’t know. Giving out drugs in the hopes that they might work is not only unscientific but also dangerous.

“A common interpretation of off-label use and compassionate use of drugs is that if the patient died, they died from the disease, but if the patient survived, they survived because of the given drug,” Kalil wrote in a column published March 24 in the Journal of the American Medical Association. “This is not true.”

We do know that the drugs being considered come with their own risks. Both chloroquine and hydroxychloroquine, for example, can cause a potentially life-threatening type of heart arrhythmia known as QT prolongation. If those drugs end up being ineffective at treating COVID-19, using them could put a patient’s life at risk for nothing.

“What happens if you combine those two [drugs]? We actually don’t know,” said Almut Winterstein, a pharmacoepidemiologist at the University of Florida. “You could get severe arrhythmia. It could kill people. This is where clinical trials become very important.”

With the 2014-2016 Ebola virus outbreak, many doctors took the “let’s just try it” approach, without control trials, Kalil said. Because of this, we still don’t know whether some of those treatments worked or were actually hastening death instead of healing patients.

“I could list for hours the number of drugs and medications that were given to patients with Ebola, and I can tell you that we found absolutely nothing,” Kalil said. “People definitely were harmed by these drugs, and we’re never going to know because nothing was given with controls.”

The gold standard for researching new treatments is conducting randomized controlled trials, in which one group is randomly assigned to take the drug being tested and the other group gets a placebo. If people in the group taking the drug recover more quickly than those taking the placebo, it’s a good indicator that the drug works.

No drugs currently on the market have previously gone through control trials to treat COVID-19 specifically. Because of this, we can’t be certain how effective or safe they would be. And even when a treatment seems promising, it may not end up being effective: Lopinavir-ritonavir, a combination of anti-HIV drugs, was considered a possible treatment for COVID-19, but a clinical study published March 18 showed the pair had no substantial benefit on patients.

Other clinical trials for existing medications, such as remdesivir, have already begun, including one sponsored by the National Institutes of Health and led by Kalil. It will take weeks, and possibly months, for the trials to be completed, and there’s a chance that none of the drugs being investigated will effectively treat COVID-19. But it’s the only hope we have of figuring out whether these drugs actually work and are safe to use.

“I understand we are all anxious to get everything as fast as possible,” Kalil said. “But the moment you compromise quality, the moment you don’t do the science correctly, you may end up hurting more people.”

Kaleigh Rogers is FiveThirtyEight’s technology and politics reporter.