WASHINGTON - A clinical trial to evaluate the safety and effectiveness of hydroxychloroquine, an antimalarial drug, for the treatment of adults hospitalized with COVID-19 has begun in the United States, according to a release of the National Institutes of Health (NIH) on Thursday.

The first participants have enrolled in the trial at Vanderbilt University Medical Center, Tennessee.

The blinded, placebo-controlled randomized clinical trial aims to enroll more than 500 adults who are currently hospitalized with COVID-19 or in an emergency department with anticipated hospitalization.

All participants in the study will continue to receive clinical care as indicated for their condition. Those randomized to the experimental intervention will also receive hydroxychloroquine, according to the NIH.

"Effective therapies for COVID-19 are urgently needed," said James Kiley, director of the Division of Lung Diseases of the National Heart, Lung, and Blood Institute, part of the NIH.

"Hydroxychloroquine has showed promise in a lab setting against SARS-CoV-2, the virus that causes COVID-19 and preliminary reports suggest potential efficacy in small studies with patients. However, we really need clinical trial data to determine whether hydroxychloroquine is effective and safe in treating COVID-19," he said.

US President Donald Trump confirmed the clinical trial at a White House daily briefing, saying the country is ramping up hydroxychloroquine production, and the federal government has stockpiled millions of doses of hydroxychloroquine.

Trump said a lot of drugs have been sent to Michigan for testing.

US Vice President Mike Pence said on Sunday hydroxychloroquine will be used in a trial covering 3,000 patients at a hospital in Detroit, Michigan, and the results will be tracked in a formal study.

While COVID-19 usually presents as an acute respiratory infectious illness, it can damage multiple organ systems, including heart, lung, and blood.

Currently, no therapies have been demonstrated to prevent the progression of COVID-19 to severe illness, but several medicines available in the United States have been proposed as potential therapies, said the NIH.

Hydroxychloroquine is used to treat malaria and rheumatoid conditions such as arthritis. In various studies, the drug has demonstrated antiviral activity, an ability to modify the activity of the immune system, said the NIH.

The drug has an established safety profile at appropriate doses, leading to the hypothesis that it may also be useful in the treatment of COVID-19, according to the NIH.

The drug is not without risks as even short term use can cause cardiac arrythmias, seizures, dermatological reactions, and hypoglycemia, said the NIH.

"Many US hospitals are currently using hydroxychloroquine as first-line therapy for hospitalized patients with COVID-19 despite extremely limited clinical data supporting its effectiveness," said Wesley Self, emergency medicine physician at Vanderbilt University Medical Center and head of the trial in Tennessee.

"Thus, data on hydroxychloroquine for the treatment of COVID-19 are urgently needed to inform clinical practice," Self said.