On Friday, the U.S. Food and Drug Administration warned on the use of malaria medication hydroxychloroquine in coronavirus patients, even as United States President Donald Trump, who believed it was a "game changer," called for further study.

According to a study submitted for expert review on Tuesday, the vaccine, first approved in 1955, offered little benefit and potentially risk of mortality for patients at U.S. veterans hospitals.

The health authority documented cases of severe heart rhythm issues in patients with coronavirus who had been administered with the medications that were initially used to combat malaria, a parasitic infection.

The two drugs at issue are synthetic analogs of quinine, a compound derived from tree bark and used for centuries as an antimalarial. More recently, it was shown that quinine analogs offer a good variety of effects above parasite prophylaxis, especially as medications for lupus and other severe autoimmune diseases.

The Food and Drug Administration has released a MedWatch Health warning about the use of hydroxychloroquine or chloroquine for COVID-19 diagnosis on April 24.

Following initial studies suggesting that hydroxychloroquine may help improve some patients with severe COVID-19 symptoms, the FDA issued an Emergency Use Authorization (EUA) to enable physicians to use the medication on patients whose symptoms are not improving. Several research have also been conducted to study its effectiveness as a remedy for COVID-19.

"We'd like to remind health care professionals and patients of the "known risks linked with both hydroxychloroquine and chloroquine," the FDA disclosed on its website, referring also to a similar drug.

COVID-19, the infection caused by the novel coronavirus, has no approved treatment or vaccine. But hydroxychloroquine was commonly used in an effort to change the progression of the COVID-19 disease on the basis of anecdotal reports that it might offer some relief.

Numerous randomized trials are ongoing in the US and elsewhere, with the National Institutes of Health initiating a review last week to examine the safety and efficacy of hydroxychloroquine.

Novartis markets hydroxychloroquine, and the multinational pharmaceutical company is currently performing a randomized trial of COVID-19 patients into groups receiving either the medication or a placebo.

Nonetheless, at the moment there is nothing but anecdotal data to indicate that quinine analogs successfully counter coronavirus.

If the results of Novartis clinical trials demonstrate a clear impact and benefit, the FDA will rapidly change its recommendations. Health care providers have until then had to view quinine analogs as too dangerous for patients outside a hospital environment.