Efficacy of the Therapy With BRAINMAX® Using fMRI for the Treatment of Patients With Asthenia After COVID-19

Inclusion Criteria: * Patients able to sign the patient informed consent form for the participation in the clinical study * Patients of both sexes of 25-50 years of age * Patient's negative test result for severe acute respiratory syndrome (SARS) -CoV-2 RNA obtained by polymerase chain reaction (PCR) method within 72 hours * COVID-19 diagnosis documented in the history more than 12 weeks ago\* * Symptoms of Post-COVID-19 syndrome (asthenic state, feeling of energy loss and decreased functioning, intellectual function disorder, attention and memory disorder, emotional lability, reducing stress resistance) which appeared during or after COVID-19, retain for more than 12 weeks and cannot be explained by an alternative diagnosis * Patients capable of following the requirements of the Clinical Study Protocol * Negative pregnancy test result (for women with the active childbearing potential) * MFI-20 scale score is more than 30 at the moment of screening. * Higher education. * Lack of decompensated somatic pathology * Lack of indications of the transferred/current disease of the nervous system Exclusion Criteria: * Allergic reactions to the components of the study product * Taking prohibited drugs/dietary supplements during the previous randomization of the month * Severe hepatic failure * Severe renal failure * Chronic liver and hepatic diseases * Thyroid diseases * Anaemia * Malignant tumour of any localization currently or during 5 years before the inclusion into the study except for completely treated carcinoma in situ * Autoimmune diseases * Other chronical diseases which, according to the investigator, can cause asthenia * Pregnancy or lactation period * Tuberculosis, cancers or positive reaction to the HIV infection, hepatitis B \& C, syphilis according to the history data * Severe eyesight and/or hearing disorders, serious articulation disorders and/or other deviations able to prevent the patient from adequate cooperation during the study) * Mental disorders in the history * Alcohol, drug abuse or drug dependence in the history * Patients which, according to the investigator, are obviously or probably incapable of understanding and evaluating this study information within the process of the informed consent form signing, including but not limited to with regard to expected risks and possible discomfort * Other diseases, symptoms or conditions not listed above, which, according to the investigator, are predicaments for the participation in the clinical study * The presence of contraindications for MRI * The presence of contraindications for taking the drug Contraindications for MRI: * Electronic medical devices in the body (cardiomyostimulator and other) * Metal elements in the study area (prosthesis, clamp, fragment) * Invariable behavior of patients * Inability to remain still during MRI Prohibited drugs/dietary supplements: * Ethyl methyl hydroxypyridine succinate and Meldonium (other than the one studied in the study) * Psychotropic medication * Drugs containing succinic acid and its salts * Drugs containing vitamin B6 and /or its derivatives * Antioxidants, antihypoxic drug and metabolic drugs * Nootropic drugs