Two anti-malaria medications highly touted by President Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE should not be taken outside a hospital or clinical trial because of the risk of severe heart problems, the Food and Drug Administration (FDA) warned Friday.

The FDA said it issued the warning because of numerous reports about serious cardiac events and death in patients with COVID-19 receiving hydroxychloroquine and chloroquine, either alone or combined with the antibiotic azithromycin.

"Hydroxychloroquine and chloroquine can cause abnormal heart rhythms ... and a dangerously rapid heart rate called ventricular tachycardia," the agency said. "These risks may increase when these medicines are combined with other medicines ... including the antibiotic azithromycin."

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The FDA emphasized that hydroxychloroquine and chloroquine are not approved for treating or preventing COVID-19. They are currently being studied in clinical trials, and the agency has made them available in the Strategic National Stockpile under an Emergency Use Authorization.

The warning from FDA comes on the heels of a separate warning from a panel of doctors and experts convened by the National Institutes of Health.

Earlier this week, the COVID-19 Treatment Guidelines Panel advised against combining hydroxychloroquine and azithromycin outside of clinical trials.

The panel said there is not enough clinical data to recommend either for or against the use of hydroxychloroquine for the treatment of COVID-19.

The evidence on hydroxychloroquine is conflicting, at best, and mostly anecdotal.

Hospitals have widely administered the drug to patients with COVID-19 in the hope that it would help, but there has been little evidence to prove its effectiveness. Multiple clinical trials are currently underway in the U.S., but none have published results yet.

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Despite health experts' warning against the risks of an unproven treatment, President Trump has latched on to the use of chloroquine and hydroxychloroquine, as well as the combination drugs, as a potential "game changer" for COVID-19 patients.

The drugs, "taken together, have a real chance to be one of the biggest game-changers in the history of medicine," Trump tweeted last month.

This week, a top federal health official responsible for coordinating vaccine research and development alleged he was forced out of his position because he would not promote the wide use of hydroxychloroquine.