(Photo: AP)

WASHINGTON, April 24 (Xinhua) -- The U.S. Food and Drug Administration (FDA) on Friday cautioned against the use of hydroxychloroquine or chloroquine for COVID-19 outside of the hospital setting or a clinical trial due to risk of heart rhythm problems.

"The FDA is aware of reports of serious heart rhythm problems in patients with COVID-19 treated with hydroxychloroquine or chloroquine, often in combination with azithromycin and other QT prolonging medicines," said the agency in a release.

"We are also aware of increased use of these medicines through outpatient prescriptions," said the FDA.

Hydroxychloroquine and chloroquine can cause abnormal heart rhythms such as QT interval prolongation and a dangerously rapid heart rate called ventricular tachycardia, according to the FDA.

These risks may increase when these medicines are combined with other medicines known to prolong the QT interval, including the antibiotic azithromycin, which is also being used in some COVID-19 patients without FDA approval for this condition, said the FDA.

Patients who also have other health issues such as heart and kidney disease, are likely to be at increased risk of these heart problems when receiving these medicines, said the FDA.

The agency said it will continue to investigate risks associated with the use of hydroxychloroquine and chloroquine for COVID-19 and reveal to the public when more information is available.

The FDA authorized temporary use of hydroxychloroquine and chloroquine only in hospitalized patients with COVID-19 when clinical trials are not available, or participation is not feasible, through an Emergency Use Authorization.