The anti-malarial drug US President Donald Trump has been taking is tied to an increased risk of death in hospitalised Covid-19 patients, a large study has found.
The study, which was published in medical journal The Lancet, looked at more than 96,000 people hospitalized with Covid-19, the respiratory disease caused by the new SARS-CoV-2 coronavirus.
Those treated with hydroxychloroquine, or the closely related drug chloroquine, had a higher risk of death and heart rhythm problems than patients who had not been given the medicines.
The study, published Friday, also found no benefit to taking the drugs for coronavirus patients.
Demand for the decades-old hydroxychloroquine has surged as Trump repeatedly promoted its use against the coronavirus, urging people to try it. "What have you got to lose?" he asked.
Trump said this week he has been taking hydroxychloroquine as a preventative medicine, despite a lack of scientific evidence.
The Lancet study authors suggested hydroxychloroquine and chloroquine should not be used to treat Covid-19 outside of clinical trials until studies confirm their safety and efficacy in such patients.
Where do these drugs sit?
There is a frantic search for drugs to treat people who have become ill with Covid-19, while research teams around the world also pursue a safe and effective vaccine to combat the virus.
Internationally more than 335,000 people have died from Covid-19, and sickened millions more.
The US Food and Drug Administration has allowed healthcare providers to use the drugs for Covid-19 through an emergency-use authorization, but has not approved them to treat it.
On April 30, it cautioned against using the drugs outside hospitals or clinical trials. The drug has been tied to dangerous heart rhythm problems.
Dr Mandeep Mehra, one of The Lancet study's authors, said the research shows that the USFDA should withdraw the emergency-use authorization for Covid-19 patients.
"That will help move this towards more, stronger evidence, because it will then force the use of these drugs only in the setting of control trials," Mehra said in an interview. "That would be an extremely wise decision."
This study and others
The multinational Lancet study looked at data from 671 hospitals where 14,888 patients were given either hydroxychloroquine or chloroquine, with or without an antibiotic, and 81,144 patients were not given such treatments.
Both drugs had shown evidence of effectiveness against the coronavirus in a laboratory setting, but studies in patients had proven inconclusive. Several small studies in Europe and China spurred interest in using hydroxychloroquine against Covid-19, but were criticized for lacking scientific rigor.
Several more recent studies have not shown the drug to be an effective Covid-19 treatment. Last week, two studies published in the medical journal The BMJ showed patients given hydroxychloroquine did not improve significantly over those who were not.
Hydroxychloroquine is used to treat lupus and rheumatoid arthritis as well as malaria.
Some proponents of using hydroxychloroquine and chloroquine for Covid-19 argue that the drugs may need to be administered at an earlier stage to be effective.
There are ongoing randomized, controlled clinical trials to study the drug's effectiveness in preventing infection by the coronavirus, as well as treating mild to moderate Covid-19. Some of those may yield results within weeks.