Paris (AFP)

Neither chloroquine nor its derivative hydroxychloroquine prove effective against Covid-19 in hospital patients, and these molecules even increase the risk of death and cardiac arrhythmia, warns a large study published Friday in The Lancet, which recommend that they not be prescribed outside of clinical trials.

Carried out on nearly 15,000 patients, this is the "first large-scale study" to show "robust statistical evidence" that these two treatments that are so much in the news, "do not benefit patients of Covid-19 "said Dr. Mandeep Mehra, lead author of the study published in the prestigious medical journal, in a statement.

These patients received four different combinations based on chloroquine (an anti-malarial) and hydroxychloroquine (prescribed for rheumatoid arthritis for example): the treatments were either administered alone or combined with an antibiotic from the macrolide family.

The study analyzed data from approximately 96,000 SARS-CoV-2 infected patients admitted to 671 hospitals between December 20, 2019 and April 14, 2020, discharged or deceased since. About 15,000 of them received one of the four combinations (chloroquine alone or combined with the antibiotic, hydroxychloroquine alone or combined with the same antibiotic), then these four groups were compared to the 81,000 patients in the control group who did not not received this treatment.

Result, the four treatments were all associated with a much higher risk of mortality than in the control group (which was 9.3%): 16.4% of deaths for chloroquine alone, 22.2% when it was combined with the antibiotic; 18% for hydroxychloroquine alone, and 23.8% when it was combined with the same antibiotic.

The authors estimate that the risk of mortality is 34% to 45% higher in patients taking these treatments than in patients with comorbidity factors, that is to say risk factors.

They also discovered serious, more frequent serious cardiac arrhythmias in patients receiving chloroquine or hydroxychloroquine, especially with the hydroxycholroquine / macrolide combination (8% of patients versus 0.3% in the control group).

The risk of arrhythmia would ultimately be five times higher with the intake of these two molecules, even if the cause and effect link is not directly proven, explain the authors who ask for an "urgent" confirmation via randomized clinical trials (patients chosen by lot) before any conclusion.

Pointing out that preliminary small-scale studies have already "failed to identify robust evidence of benefit" from these two treatments, "we now know from our study that the chances of improving" the condition of Covid-19 patients "are rather thin," writes Dr. Frank Ruschitzka, from the Zurich University Hospital, co-author.

While several countries like Brazil are betting on the use of chloroquine and its derivative, the study recommends that these treatments not be administered outside of clinical trials.

Hydroxychloroquine is currently being tested in several clinical trials, including the European Discovery trial.

© 2020 AFP