Chloroquine phosphate and hydroxychloroquine sulfate are used for treatment and prevention of complications associated with COVID-19. The use of these drugs has the potential to cause QT interval prolongation. The combination of antimalarial drugs with fluoroquinolones and macrolides increases the risk of rhythm disturbance. Objective. Based on analysis of own clinical data to determine the QTc-interval value for correction of monitoring of patients with COVID-19-associated extra-hospital pneumonia during antiprotozoic course in combination with antibacterial agents with cardiovascular toxicity (macrolide or fluoroquinolone). Material and methods. A single-center non-randomized prospective study to evaluate the safety of therapy in 98 patients with COVID- 19 community-acquired pneumonia. Patients were divided into two subgroups: patients with (n=39) and without (n=59) cardiovascular diseases. Results. QTc prolongation from baseline (360 ms, from 350 to 380) was observed on fifth (390 ms, from 360 to 400; p=0.003) and 10th (400 ms, from 390 to 430; p=0.005). In patients with cardiovascular diseases, QTc prolongation from baseline was detected only on the 10th day (360 ms, from 340 to 410 ms vs 400, from 370 to 450 ms; p=0.03). Conclusions. Co-administration of hydroxychloroquine sulfate with fluoroquinolones or macrolides in patients with COVID- 19 was not associated with severe QTc prolongation or arrhythmias.