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.

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.