Randomized, Double-blind, Placebo-controlled Trial of the Efficacy and Safety of Tianeptine in the Treatment of Covid Fog Symptoms in Patients After COVID-19. (COVMENT)

Inclusion Criteria: Written informed consent from the patient to participate in the clinical trial. Age ≥ 18 years. History of COVID-19 infection confirmed by a positive SARS-CoV-2 test result by RT- PCR or positive antigen test. Subjective patient-reported cognitive decline after COVID-19 infection at Screening. Cognitive dysfunction found at Screening, defined by the Montreal Scale for the Assessment of Cognitive Function (MoCA) as a score of less than 26. Use of effective contraception by women of childbearing potential. Exclusion Criteria: Hypersensitivity to tianeptine. Hypersensitivity to fluorodesoxyglucose (FDG). History of allergy to drugs or other substances, which, in the Investigator's opinion, is a contraindication to participation in the study. History of stroke. Ever undergone and planned brain surgery at the time of the study. Previously diagnosed organic damage to the central nervous system. Diagnosed organic mental disorder. Diagnosed bipolar affective disorder. Diagnosed psychotic disorder. History of active depressive episode, including those diagnosed at the time of study eligibility, requiring antidepressant treatment. Diagnosed mental retardation. Bipolar affective disorder in a first-degree relative. Uncontrolled diabetes mellitus. Severe renal failure with eGFR < 30ml/min/1.73 m2. cirrhosis of liver Severe liver cirrhosis (Child-Pugh class C ). Claustrophobia. Diagnosed chronic diseases that significantly worsen the patient's prognosis and quality of life, which, in the Investigator's opinion, may adversely affect the patient's participation in the study. Active or past malignancy within the past 5 years, except for basal cell carcinoma of the skin and cervical cancer in situ in patients who have received radical treatment. Active viral, bacterial, fungal, tuberculous, or parasitic infection. History or presence of other relevant diseases which, in the Investigator's opinion, is a contraindication to participation in the study. Positive pregnancy test performed on women of childbearing potential at screening or Visit 1. Taking medications: Non-selective MAO inhibitors within 14 days prior to screening, Mianserin during screening. Significant difficulty with peripheral venous cannulation. Positive history of alcohol, drug, and psychoactive abuse/dependence. Pregnancy or planning a pregnancy during the study period. Breastfeeding or planning to breastfeed during the study period. Current participation in another clinical trial. Lack of patient compliance.