Inclusion Criteria:  Patients of both sexes, 18-90 years of age. Patient requiring oxygen therapy, SpO2 <94%. Confirmed COVID-19 infection. At least one risk factor for increased mortality in the course of COVID-19: currently published in the literature e.g. smoking, hypertension, diabetes, cardiovascular disease. Documented informed consent according to ICH-GCP and national regulations.  Exclusion Criteria:  Chronic bronchitis, emphysema, interstitial lung disease, or other history of lung disease. Contraindications to the use of spironolactone. Hypersensitivity to spironolactone or any of the excipients. Pregnant patients (pregnancy test will be performed in every patient of reproductive age) and during lactation. Patients with mental illness or dementia who are unable to give informed consent to the examination. ARDS caused by another viral infection (SARS-CoV-2 negative). ARDS from other causes/trauma. Ionic disorders: hyperkalemia, hyponatraemia. Adrenal crisis. Acute and chronic renal failure, creatinine clearance less than 30 ml/min. Anuria. Porphyria.