Hydroxychloroquine, derivative of the common malaria drug chloroquine initially thought to be a promising drug in the fight against Covid19, due to its anti inflammatory and anti viral effects, but subsequent trials questioned its efficacy as no statistical benefit was seen.
However research trials were still ongoing e.g the Solidarity trial now The World Health Organization (WHO) has suspended testing the malaria drug hydroxychloroquine in COVID-19 patients because of safety concerns, WHO Director said.
Though a safer alternative to chloroquine, HCQ still affects the QT interval, that may lead to life threatening heart rhythm abnormalities, in predisposed individuals or when used in combination with other medications, and needs frequent monitoring.
HCQ is no longer recommended to be used for Covid19 treatment or for prophylaxis.