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The lack of vaccines and treatment for the novel coronavirus has allowed it to sweep the planet virtually unchecked. With a regimen of hunkering down and hand-washing the only effective way to slow its path, national leaders are desperate to find a medicine that could have an effect. But President Trump’s cheerleading for anti-malarial drugs has raised hopes beyond what is supported by the scientific facts.

What are chloroquine and hydroxychloroquine?

Bayer invented the medicine chloroquine in 1934, and it has been used for decades to treat malaria throughout the world. Hydroxychloroquine was invented during World War II to provide an alternative with fewer side effects.

Hydroxychloroquine, sold under the brand name Plaquenil, is also used by patients with lupus and rheumatoid arthritis to control inflammation. Both drugs, chloroquine and hydroxychloroquine, are available as generics, but public and political interest has caused runs, hoarding and severe shortages in recent weeks.

Despite the lack of rigorous evidence, Trump has promoted the drugs as important treatments for covid-19, the disease the coronavirus causes, and the Food and Drug Administration has issued an emergency authorization to permit their widespread use to treat severely ill patients in hospitals.

What evidence is there that they work to treat coronavirus?

There is no clear evidence that the drugs work against the coronavirus, despite their use by hospitals and doctors in the United States and other countries since the outbreak began. Their antiviral properties have been proved in test tubes, but rigorous clinical trials to test their effectiveness in humans have not been completed.

Limited studies on coronavirus patients have been published by researchers in France and China, but their extremely small size and other problems prevented them from being statistically significant. The French study included a combination of hydroxychloroquine with the antibiotic azithromycin that showed benefit in six patients, results that Trump has touted. Another study in 11 patients in France showed no evidence the regimen works. A Chinese study also showed no benefit over the standard course of treatment.

What does mainstream science say?

Mainstream scientists caution against using the drugs without more evidence they are effective. Anthony S. Fauci, chief of the National Institute for Allergy and Infectious Diseases, has accompanied Trump at the White House lectern and openly rebutted his declarations that the drugs are “game-changers” in the fight against the coronavirus.

Trump prevented Fauci from answering a question about the subject on Sunday, but that has not changed the assessment among academics that there is not enough evidence about the ability of these drugs to reduce viral load and prevent the inflammatory response that devastates the lungs of seriously ill coronavirus patients. The FDA was equivocal about possible benefits when it issued its emergency use authorization last month: “It is reasonable to believe that chloroquine phosphate and hydroxychloroquine sulfate may be effective in treating covid-19,” the agency said.

What are the dangers of side effects with these drugs?

The dangerous side effects of the drugs are much better known. Most seriously, the drugs can trigger arrhythmia, which can lead to a fatal heart attack in patients with cardiovascular disease or who are taking certain drugs, including anti-depression medications. Doctors recommend screening with an electrocardiogram to prevent the drug from being given to the 1 percent of patients at the greatest risk of a cardiac event. The drugs also can cause vision loss called retinopathy with long-term use, and chloroquine has been associated with psychosis.

Why does Trump keep touting their benefits?

As the coronavirus has spread from China across the world and to the United States, the dire reality is that there is no vaccine and no approved drug available to treat the serious respiratory symptoms that are claiming thousand of lives.

In repeatedly trumpeting unproven drugs from the White House briefing room, Trump has rallied elements of his base around the potential for a cure and sought to portray himself as a wartime president taking action. Trump has said he is eager to push the FDA to approve drugs and get them into hospitals quickly, regardless of the lack of evidence that they work. “The president is talking about hope for people. And it’s not an unreasonable thing to hope for people,” Fauci said at the White House on March 21.