President Trump has been a vocal supporter of using the anti-malarial drug hydroxychloroquine as a potential treatment for Covid-19, the disease caused by the new coronavirus, but many experts believe evidence supporting the drug as safe Covid-19 treatment is lacking.

In a White House news briefing on Saturday, Trump said of the drug, "What do [patients] have to lose? Take it. I really think they should take it. But it's their choice and it's their doctor's choice, or the doctors in the hospital. But hydroxychloroquine—try it, if you'd like."

What the evidence says

Hydroxychloroquine is used to prevent and treat a specific type of malaria and has been used to treat lupus and rheumatoid arthritis.

However, the drug hasn't been proven to successfully treat Covid-19 in any large clinical trials. Last week, researchers from China made public a small trial that found hydroxychloroquine helped improve Covid-19 recovery rates in moderately ill patients. However, the study was not peer-reviewed and came with notable limitations. For instance, Luciana Borio, who oversaw public health preparedness for the National Security Council in the Trump Administration and was the acting chief scientist at FDA under former President Barack Obama, explained that the trial included only young and middle-aged patients with mild Covid-19 cases.

Other studies purporting hydroxychloroquine's effectiveness against Covid-19 have come out of France and China. However, experts have criticized those findings because the trials lacked control groups, which means the researchers could not definitively determine whether the drugs were responsible for any improvement in patients' conditions.

"Hydroxychloroquine has been studied as a possible antiviral therapy for many decades. Despite showing evidence of activity against several viruses in the laboratory, it never showed success in randomized clinical trials," Borio said.

What the experts say

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, has said that Americans should not think of hydroxylchloroquine as a "knockout drug" for Covid-19. "In terms of science, I don't think we could definitively say it works," he said.

Megan Ranney, an emergency physician at Brown University, said while "[t]here may be a role for [hydroxychloroquine] for some people," there's not enough scientific evidence to support claims that hydroxychloroquine works as a treatment for Covid-19. Further, Ranney said the drug can cause negative  side effects. "It causes psychiatric symptoms, cardiac problems, and a host of other bad side effects."

Kenneth Klein, a consultant who helps drug companies design and evaluate clinical trials, said patients with heart problems and other underlying medical conditions have a high risk of experiencing negative side effects from hydroxychloroquine. Even patients with healthy hearts could develop a fatal arrhythmia as a result of taking hydroxychloroquine, Klein said.

On March 25, the American Medical Association and two pharmacists' associations issued a joint statement saying that providers have been prescribing chloroquine and hydroxychloroquine for families and colleagues, and that some hospitals and pharmacies have bought "excessive amounts of these medications in anticipation of potentially using them for Covid-19 prevention and treatment." The organizations said they "strongly oppose these actions" and warned that there could be "grave consequences for patients with conditions such as lupus or rheumatoid arthritis if the drugs are not available in the community."

FDA grants drugs emergency use authorizations

Despite the lack of evidence supporting the drugs as treatments for Covid-19, FDA last week gave providers permission to use hydroxychloroquine to treat the disease. FDA's emergency use authorization states that hydroxychloroquine "supplied from the Strategic National Stockpile" can be used "to treat adults and adolescents who weigh 50 kg or more and are hospitalized with Covid-19 for whom a clinical trial is not available, or participation is not feasible."

On Sunday, Vice President Pence announced that a 3,000-person study on the effectiveness of hydroxychloroquine as a Covid-19 treatment would take place at Henry Ford Hospital.

Participants in the study, who will be front-line health care workers, will receive either a once-a-week dose of hydroxychloroquine, a once-a-day dose, or a placebo, and will not know which group they're in. After eight weeks, participants will be checked for symptoms and results "will be compared among the three groups to see if the medication had any effect," Henry Ford Health System said in a statement.

William O'Neill, an interventional cardiologist and researcher with Henry Ford and organizer of the study, said the study will be "the first major, definitive study in health care workers and first responders of hydroxychloroquine as a preventive medication" (Crowley et. al., New York Times, 4/5; Perper, Business Insider, 4/5; Yen et. al., Associated Press, 4/6; Coleman, The Hill, 4/5; Falconer, Axios, 4/5).