Fail to work, increase death rate and cause cardiac arrhythmias."We were unable to confirm a benefit of hydroxychloroquine or chloroquine, when used alone or with a macrolide, on in-hospital outcomes for COVID-19. Each of these drug regimens was associated with decreased in-hospital survival and an increased frequency of ventricular arrhythmias when used for treatment of COVID-19."
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31180-6/fulltext
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31180-6/fulltext