Summary:
What is already known
Drugs that block hERG potassium channels in the heart have potential to cause cardiac arrhythmias
Hydroxychloroquine, chloroquine and azithromycin can block hERG potassium channels
What this study adds
Disease associated metabolic changes such as febrile temperature, acidosis and electrolyte imbalance modify hERG potency and hence proarrhythmic risk
Chronic exposure to hydroxychloroquine and azithromycin causes additional prolongation pf repolarisation compared to their acute effects
Clinical significance
There is significant proarrhythmic risk for hydroxychloroquine and chloroquine at doses being proposed to treat COVID-19
Clinicians should implement long term QT interval monitoring in trials, particularly in patients with electrolyte imbalances