The French study of hydroxychloroquine, posted Tuesday to MedRxiv, followed a more conventional design. Researchers there enrolled 181 COVID-19 patients who were admitted to four French hospitals over the last two weeks of March, then compared the outcomes of 84 people who quickly received hydroxychloroquine to 91 patients who never received the drug. (Patients in both groups got a range of other treatments, including antiviral medications, corticosteroids and breathing support.)

The researchers found that treatment with hydroxychloroquine did not reduce the likelihood that a COVID-19 patient would die or be admitted to the intensive care unit within a week of hospital admission. Nor did it drive down a patient’s likelihood of developing serious breathing problems.

Hydroxychloroquine did, however, raise some risks. Eight of the 84 patients who got hydroxychloroquine experienced changes in heart rhythm that required discontinuation of the drug, and another patient developed a related heart-rhythm disorder.