GENEVA (BLOOMBERG) - An international trial using hydroxychloroquine to treat Covid-19 patients will be restarted after questions arose about a study linking the antimalarial drug to increased death and heart risks.

The World Health Organisation (WHO) said on Wednesday (June 3) that it will resume recruiting patients for the hydroxychloroquine arm of a global trial called Solidarity.

The agency had paused the branch of the experiment, which compares the impact of a number of treatment regimens, after the drug was linked to heart risks in research published in the Lancet, a medical journal.

The move adds to the confusion that's erupted since more than 200 scientists began questioning the study published May 22.

Scrutiny has focused on Surgisphere, the Chicago-based firm that provided data for the investigation, with demands for more transparency about its sources and methods of analysis.

The WHO paused the hydroxychloroquine component as a precaution "because of concerns raised about the safety of the drug," director-general Tedros Adhanom Ghebreyesus said at a press briefing.

After a safety panel review, "the members recommend that there are no reasons to modify trial protocol."

US President Donald Trump has touted hydroxychloroquine, saying he has taken it as a preventative against the coronavirus.

Use of the drug has since become politically charged, and several studies - including the Lancet article - have raised safety worries about the pills in Covid-19 patients.

CONCERN ABOUT RESEARCH

Both the Lancet and the New England Journal of Medicine, two of the top medical journals in the world, have expressed concern about research using Surgisphere's data.

The government of France, which last week ruled against the use of hydroxychloroquine in Covid patients, has written to the Lancet to request a review of the raw data.

The journal has said it stands by the conclusions of the study.

Surgisphere has said it cannot reveal some details of its sources because of agreements with hospitals and governments, and that it takes data security and privacy seriously.

Mandeep Mehra, a cardiologist at Harvard-linked Brigham and Women's Hospital, said researchers who are not affiliated with Surgisphere are reviewing the data used in both papers and will provide the findings to the journals.

Mehra worked on the Lancet hydroxychloroquine trial, as well as a study in the New England Journal.

Meanwhile, the WHO said it will continue its trial of hydroxychloroquine in hopes of determining whether the drug benefits Covid patients.