Coadministration of remdesivir and hydroxychloroquine has not been studied and is not recommended as it may result in reduced antiviral activity of remdesivir. In vitro studies show that chloroquine reduced the formation of the virally active remdesivir triphosphate in normal human bronchial epithelial cells and a similar interaction may occur with hydroxychloroquine. Due to the long elimination half life of hydroxychloroquine, this effect is expected to persist even if hydroxychloroquine is stopped prior to the initiation of remdesivir (washout period 180 days). No significant effect on hydroxychloroquine is expected. In addition, caution should be exercised as both drugs have risks of QT prolongation and/or TdP on the CredibleMeds.org website (possible risk for remdesivir; known risk for hydroxychloroquine).