Multiple drugsQTc prolongation and off-label use: case report A 69-year-old man developed QTc prolongation during off-label treatment with hydroxychloroquine for COVID-19 pneumonia. Additionally, he also received off-label treatment with azithromycin, lopinavir/ritonavir and tocilizumab for COVID-19 pneumonia [not all routes stated].The man presented to the emergency department with stabbing pain in his right lower limb for 2h along with chest pain, dyspnoea, profuse diaphoresis and presyncope. He had a history of hypertension, chronic obstructive pulmonary disease, obstructive sleep apnoea syndrome, undifferentiated arthritis and morbid obesity, and he had been receiving various medications including sulfasalazine, acemetacin, valsartan, atenolol and hydrochlorothiazide. Twenty seven days prior to the admission, he came in contact with his son, who was positive for COVID-19. After further investigations, he was diagnosed with massive pulmonary embolism. He started receiving alteplase, followed by enoxaparin sodium [enoxaparin]. Chest CT scan was suggestive of severe COVID-19 pneumonia. Considering the severe pneumonia and thrombus burden, alteplase was stopped, and he was transferred to the COVID-19 ICU. He started recieivng off-label treatment with oral hydroxychloroquine 200mg three times per day, oral azithromycin 500 mg/day and oral lopinavir/ritonavir 200/50mg twice per day. Concomitantly, he also received paracetamol and ceftaroline fosamil [ceftaroline]. On day 3, he was started on mechanical ventilation due to diagnosis of acute respiratory distress syndrome. He developed hypotension as a side effect of sedation (details not stated), for which he started receiving norepinephrine. However, he developed QTC prolongation (up to 560ms) [time to reaction onset not stated].Hence, hydroxychloroquine was discontinued. The man then received three doses of tocilizumab 800mg three times per day (offlabel use), and enoxaparin sodium was continued. During day 5-8, he received three doses of hyperimmune plasma each day with improvement. On day 9, azithromycin was stopped, and lopinavir/ritonavir was discontinued after 14 days. On day 15, he developed fever, and ventilator-associated pneumonia was suspected. He was started on meropenem. After 20 days, an improvement was observed in ventilatory, clinical and laboratory parameters. Subsequently, he experienced delirium. After 29 days, he was discharged.