The FDA issued a warning against the use of hydroxychloroquine as a treatment for the coronavirus outside of a hospital or clinical trial.
According to the agency, the drug can cause "serious heart rhythm problems" in some patients, especially when used in combination with other drugs.
"Therefore, we would like to remind health care professionals and patients of the known risks associated with both hydroxychloroquine and chloroquine," the FDA's warning read. "We will continue to investigate risks associated with the use of hydroxychloroquine and chloroquine for COVID-19 and communicate publicly when we have more information."
President Donald Trump has touted the drug as an effective treatment for the coronavirus. While some studies with extremely small sample sizes have found the medication to work in battling the virus, there is more emerging evidence that the drug might not be an effective cure.
This week, the Veterans Health Administration hospitals released a study that suggested that the drug did not reduce the risk of mechanical ventialtion, and patients who took the drug experienced an increased mortality rate.
The FDA said in its statement Friday that the drug has not been yet proven as a COVID-19 treatment.
"Hydroxychloroquine and chloroquine have not been shown to be safe and effective for treating or preventing COVID-19," the statement reads. "They are being studied in clinical trials for COVID-19, and we authorized their temporary use during the COVID-19 pandemic for treatment of the virus in hospitalized patients when clinical trials are not available, or participation is not feasible, through an Emergency Use Authorization (EUA) ."
Patients who have been prescribed the drugs have reported that they're having trouble filling their prescriptions.
Doctors use hydroxychloroquine and chloroquine to treat malaria, lupus and arthritis. But since Trump began touting the drug in White House press briefings in March, the demand for the medications has skyrocketed. Patients who have been prescribed the drugs have reported that they're having trouble filling their prescriptions.