The 4-aminoquinolines, chloroquine, and hydroxychloroquine have been used for over 70 years for malaria and rheumatological conditions, respectively. Their broad-spectrum antiviral activity, excellent safety profile, tolerability, low cost, and ready availability made them prime repurposing therapeutic candidates at the beginning of the COVID-19 pandemic.
Hydroxychloroquine and chloroquine have come under intense scrutiny over the past six months as they have been proposed as treatments for COVID-19. It is widely quoted and stated that the 4-aminoquinolines chloroquine and hydroxychloroquine cause oxidant hemolysis in glucose-6-phosphate dehydrogenase (G6PD) deficiency, yet there is no convincing evidence for this claim, and there is substantial evidence against it. X-linked G6PD deficiency is the most common human enzymopathy.