Discussion
This study demonstrates that both chloroquine and hydroxychloroquine
carry cardiac safety risks that are of significant concern in the
context of therapeutic doses being proposed for treatment of COVID-19.
Furthermore, the proarrhythmic risk associated with block of hERG
channels by these compounds can be exacerbated in patients by
electrolyte abnormalities such as hypokalaemia and hypermagnesemia.
Co-administration of azithromycin with hydroxychloroquine did not
further increase prolongation of repolarisation to hydroxychloroquine
alone in the short term. However, there was a time-dependent increase in
prolongation observed with long term exposure, supporting the need for
long term QT interval monitoring in these patients.