In a brief report published today in JAMA Cardiology, a team of pharmacists and clinicians at Beth Israel Deaconess Medical Center (BIDMC) found evidence suggesting that patients who received hydroxychloroquine for COVID-19 were at increased risk of electrical changes to the heart and cardiac arrhythmias. The combination of hydroxychloroquine with azithromycin was linked to even greater changes compared to hydroxychloroquine alone. Hydroxychloroquine and azithromycin each can cause an electrical disturbance in the heart known as a QTc prolongation, indicated by a longer space between specific peaks on an electrocardiogram. QTc prolongation denotes that the heart muscle is taking milliseconds longer than normal to recharge between beats. The researchers note that the delay can cause cardiac arrhythmias, which in turn increases the likelihood of cardiac arrest, stroke, or death. “While hydroxychloroquine and azithromycin are generally well-tolerated medications, increased usage in the context of COVID-19 will likely increase the frequency of adverse drug events (ADEs),” said co-first author Nicholas J. Mercuro, PharmD, a pharmacy specialist in infectious diseases at BIDMC. Senior author Howard S. Gold, MD, an infectious disease specialist at BIDMC and an assistant professor of medicine at Harvard Medical School, said: “Based on our current knowledge, hydroxychloroquine for the treatment of COVID-19 should probably be limited to clinical trials.”