From early on in this pandemic, when people started to discuss HCQ with or without AZ, they would cite the known safety data. But what they failed to acknowledge or understand, is that that safety data was not reported from Covid-19 patients. Yes, there can be real differences in toxicity. It's what we in the clinical pharmacy world refer to as drug-disease interactions. I didn't predict problems, I was concerned that people were overlooking potential problems that had not been studied under controlled conditions. The more safe people are convinced it is, the higher the potential risk for therapeutic misadventures.
Fast forward to
"The QT interval in patients with COVID-19 treated with hydroxychloroquine and azithromycin" by Chorin et al. April 24, 2020 in Nature Medicine (I accessed it at nature.com)
The following excerpt provides preliminary evidence that yes, active Covid infection (at least higher severity cases) put patients at higher risk of toxicity. Thankfully, there were no incidents of Torsade de Pointes. Deaths in the HCQ/AZ patients were not related to arrhythmias and their ECGs were normal. But let me tell you: a mean prolongation of 24 msec and 11% incidence of QTc over 500 msec will make the cardiologists and intensivists pucker up. The patients were living in powder kegs and giving off sparks.
"The effectiveness of HZ/AZ in treating SARS-CoV-2 infection has been demonstrated in one small human study so far2. Previously, the combination of HY/AZ resulted in mild QTc prolongation when given to young healthy volunteers8. In our work, we found that in patients with COVID-19 who were treated with HY/AZ, the QTc was significantly prolonged. This discrepancy suggests that QT prolongation may be influenced by patient attributes such as the presence of co-morbidities and the severity of the disease9. Of note, recent guidance suggested ECG screening with QTc assessment for patients with COVID-19 who are candidates for novel therapies, including HY/AZ10. In our cohort, five of nine patients with severe QTc prolongation had a normal QTc at baseline. We therefore suggest that the QTc should be followed repeatedly in patients with COVID-19 who are treated with HY/AZ, particularly in those with co-morbidities and in those who are treated with other QT-prolonging medications."
I hope for the best for patients on these drugs. But don't let anyone try to convince you of their safety for Covid-19 based on old safety data in other populations.