- disease severe enough to meet the study's primary endpoint of clinical worsening (eg, current o2 saturation <92% with patient exposure to room air, current use of supplemental oxygen to maintain o2 saturation ≥ 92%). - who score ≥4 (requires oxygen therapy during hospitalization) - concomitant diseases which, in the opinion of the attending physician, prevent the patient from participating in the study, such as: decompensated cirrhosis, active ulcer disease, epilepsy and symptomatic convulsions, untreated angle-closure glaucoma determined on the basis of the patient's interview and / or medical documentation . in addition, immunocompromised patients (solid organ transplant, bmt, aids, renal failure (patients with renal impairment may develop drug poisoning) or other diseases not mentioned and other diseases treated with biological, immunological and / or steroids in high doses will not be eligible for the study. doses (> 20 mg prednisone daily). - hypersensitivity to any component of the preparation, severe congestive heart failure, cardiomyopathy, myocarditis, ii-iii degree av block, bradycardia, clinically significant prolongation of the qt interval, or a family history of congenital long qt syndrome, severe ventricular arrhythmias (including torsade de pointes), concomitant use of drugs that prolong the qt interval, hypokalaemia, hypomagnesaemia, - pregnancy, the period of breastfeeding. - parallel intake of memantine or other drugs acting on the cns (neuroleptics, anxiolytics, antiepileptic drugs, antidepressants). - other neurological conditions with agitation or confusion, delirium syndromes or psychoses. - receipt of a partial or full vaccination schedule against sars-cov-2 is also an exclusion criterion from the study.

- disease severe enough to meet the study's primary endpoint of clinical worsening (eg, current o2 saturation <92% with patient exposure to room air, current use of supplemental oxygen to maintain o2 saturation ≥ 92%). - who score ≥4 (requires oxygen therapy during hospitalization) - concomitant diseases which, in the opinion of the attending physician, prevent the patient from participating in the study, such as: decompensated cirrhosis, active ulcer disease, epilepsy and symptomatic convulsions, untreated angle-closure glaucoma determined on the basis of the patient's interview and / or medical documentation . in addition, immunocompromised patients (solid organ transplant, bmt, aids, renal failure (patients with renal impairment may develop drug poisoning) or other diseases not mentioned and other diseases treated with biological, immunological and / or steroids in high doses will not be eligible for the study. doses (> 20 mg prednisone daily). - hypersensitivity to any component of the preparation, severe congestive heart failure, cardiomyopathy, myocarditis, ii-iii degree av block, bradycardia, clinically significant prolongation of the qt interval, or a family history of congenital long qt syndrome, severe ventricular arrhythmias (including torsade de pointes), concomitant use of drugs that prolong the qt interval, hypokalaemia, hypomagnesaemia, - pregnancy, the period of breastfeeding. - parallel intake of memantine or other drugs acting on the cns (neuroleptics, anxiolytics, antiepileptic drugs, antidepressants). - other neurological conditions with agitation or confusion, delirium syndromes or psychoses. - receipt of a partial or full vaccination schedule against sars-cov-2 is also an exclusion criterion from the study.