evidence: Mehra said in an interview that the widespread use of antimalarials for covid-19 patients was based on the idea that "a desperate disease demands desperate measures," but said we have learned a hard lesson from the experience about the importance of first doing no harm. [...] There have been at least 13 studies in recent months on hydroxychloroquine or chloroquine as a treatment for covid-19 patients. They have included randomized controlled studies and observational analyses encompassing patients on the continuum from mild illness to those near death. Evidence of any benefit, such as viral clearance or improved symptoms, has been almost nonexistent. But many found an increased risk in adverse cardiac reactions — especially when combined with the antibiotic azithromycin. [...] When the first large wave of sick patients showed up at hospitals in March, doctors had little to offer them. As a result, many gambled on hydroxychloroquine. The drug had been shown to have strong antiviral properties in cell cultures, was widely available and was thought to be benign in terms of side effects. For years, hydroxychloroquine has been considered a generally safe and effective treatment for malaria, lupus and rheumatoid arthritis.