The French Medicines Agency renewed its warning to doctors on Saturday against the use of the drug hydroxychloroquine in the treatment of the emerging coronavirus (Covid-19), at a time of increasing concern about its side effects.

US President Donald Trump considered that this drug "will change the rules of the game."

The National Agency for the Safety of Medicines and Health Products has previously issued a warning about the anti-malarial drug, which is also used to treat lupus and rheumatoid arthritis.

She said that more than half of the 321 "unpleasant side effects" of the treatments currently used for the emerging coronavirus are caused by the drug hydroxychloroquine and the anti-inflammatory drug with azithromycin.

The agency reported that since the epidemic appeared, serious side effects had been reported in "80 percent" of reported cases.

She explained that four French hospital deaths were due to side effects from the treatments used for Covid-19 related to hydroxychloroquine.

The use of this controversial combination has been underlined since the publication of two small studies by Didier Raoul, a French infectious pathologist, that have proven successful in treating people with the virus for which no drug has yet appeared.

But despite growing calls in France to use the two drugs more widely, other experts have questioned Professor Raul's calls and pointed to the risk of them causing a heart attack.

On Thursday, the European Medicines Agency voiced its voice for concerns about the use of malaria drugs.

And the Amsterdam-based body stated that "recent studies have recorded serious heartbeat problems and in some cases fatal conditions when using chloroquine or hydroxychloroquine, especially when used in high doses or alongside the anti-inflammatory azitromycin."

She noted that there is no indication that these drugs are useful in treating people with the virus.

In turn, the French agency reported that 42 percent of all troubling side effects are associated with Caletra, an antiretroviral drug that confuses lopinavir and ritonavir.

Hydroxychloroquine has been known to cause heart rate problems, such as cardiac arrhythmias in some patients, which may lead to their death.

"Corona patients usually suffer from a weak heart, so they are more likely to suffer from problems with drugs that affect heart health," French agency head Dominique Martin said earlier.