Study of Open Label Losartan in COVID-19

This is an open label, phase 1 clinical trial to evaluate the safety of losartan in respiratory failure due to COVID-19. Clinical Trial setup: Detailed inclusion and exclusion criteria are listed below. Briefly, 34 patients with COVID-19 and respiratory failure who meet criteria and agree to participation in the study will be placed on losartan 25 mg daily on study day 0. If parameters are met the dose of losartan will be increased to 50 mg once daily on study day 3. Participants will continue losartan until they experience resolution of respiratory failure (normal oxygen levels on room air), are discharged from the hospital, meet stoppage criteria (detailed below) or complete 14 days of therapy. Patients and/or surrogate decision maker who do not give consent to treatment will be asked to allow collection of data from their medical record for use as a control group. Stoppage criteria for losartan * Hyperkalemia (persistent values \>5.5 mM recorded on at least 2 readings). * Worsening renal function (Cockcroft-Gault \<30 mL/min/1.73 m2) or urinary output \<20 mL/h. * Skin rashes, palpitations or other moderate or severe adverse events (interference with usual daily activities) without clear explanation should warrant immediate cessation of treatment and notification of study personnel. * Development of sustained hypotension defined as SBP \<90 mmHg, DBP \<60 mmHg recorded on at least two readings 30 min apart or use of norepinephrine \>0.1 µg/kg/min. * Any change in monitor lab parameters deemed significant and potentially related to study drug by the Investigator.