Efficacy and Safety of Vespireit, Prolonged-release Tablets, in Patients With Autonomic Dysfunction Syndrome Accompanied by Functional Vertigo

Inclusion Criteria: 1. Patient signed and dated the Informed Consent Form. 2. Males and females ≥18 to ≤ 65 years of age inclusive at the time of signing the Informed Consent Form. 3. Clinical diagnosis: G90.8 Other disorders of autonomic nervous system or G90.9 Disorder of autonomic nervous system, unspecified. 4. Diagnosed chronic functional vertigo per Barani Society criteria: total DHI score ≥ 31 points; mean MVS score ≥ 1.5 points. 5. For women of childbearing potential, a negative pregnancy test and consent to use an authorized method of contraception throughout the entire period of study participation, starting from Visit 0, and for 3 weeks after the end of the study; for men, consent to use an authorized method of contraception throughout the entire period of study participation and for 3 weeks after the end of the study. The authorized contraceptive methods in this study are: intrauterine device, barrier method, or dual barrier method (condom or occlusive cap (diaphragm or cervical/vaginal cap) plus spermicide)). Hormonal contraception was not permitted due to insufficient data on drug interactions of buspirone. Postmenopausal women (≥2 years of amenorrhea) or women who are surgically sterile (hysterectomy, bilateral ovariectomy, tubal ligation)) and men with documented infertility or vasectomy will also be eligible for the study. Non-inclusion Criteria: 1. Known or suspected hypersensitivity to the active substance or any of the excipients of the investigational drugs. 2. Lactose intolerance, lactase deficiency, glucose-galactose malabsorption. 3. A cumulative score \> 2 on the Suicide Risk Assessment Scale (SRAS). 4. Chronic heart failure III-IV functional classes according to the New York Heart Association (NYHA) classification, angina pectoris III-IV functional classes. 5. Presence of uncompensated peripheral vestibular hyporeflexia due to previous vestibular neuronitis, labyrinthitis, labyrinth trauma. 6. Presence at the time of screening of exacerbation of vestibular diseases with episodic vestibular syndrome. 7. Meniere's disease. 8. Established diagnosis of bilateral vestibular insufficiency. 9. Syncopal and presyncopal conditions at the time of screening. 10. Acute cardiovascular disease or surgical interventions (myocardial infarction, angioplasty, aortocoronary/mammary coronary heart bypass, unstable angina, and others) less than 6 months prior to the date of the Screening Visit. 11. Acute cerebral circulatory disorders and/or transient ischemic attacks less than 6 months prior to the date of the Screening Visit. 12. Hemodynamically significant cardiac rhythm and conduction abnormalities, including a history of cardiac rhythm and conduction abnormalities. 13. An installed artificial pacemaker. 14. Clinically significant ECG abnormalities; 15. Established diagnosis of liver failure, including history and/or altered laboratory values: increase in aspartateaminotransferase (AST), alanineaminotransferase (ALT) more than 2.5 times relative to the upper limit of normal, increase in total bilirubin more than 1.5 times above the upper limit of normal; 16. Established diagnosis of renal failure of any severity and/or creatinine clearance calculated by the Cockcroft-Gault formula at screening \< 80 ml/min in women and \< 90 ml/min in men. 17. Pyloroduodenal obstruction based on history. 18. Prostatic hyperplasia. 19. Thyroid function disorder according to examination and clinical and laboratory tests. 20. Parkinson's disease according to anamnesis. 21. Severe ischemic heart disease. 22. Uncontrolled hypertension with systolic blood pressure \> 180 mm Hg and/or diastolic blood pressure \> 110 mm Hg, or blood pressure (BP) at screening ≥140/90 or ≤ 100/60 mm Hg. 23. Uncontrolled diabetes mellitus, diabetes mellitus in decompensation. 24. Myasthenia gravis. 25. Closed-angle glaucoma. 26. Suspicion of elevated intraocular pressure at the time of screening. 27. Systemic connective tissue diseases. 28. Autoimmune diseases. 29. History or suspected elevated intracranial pressure. 30. Urinary retention due to a history of urethral and/or prostate disease. 31. Need for surgical and/or endovascular treatment in the next 15 months. 32. Epilepsy or convulsive seizures, including history of seizures. 33. Alcoholism, drug dependence, substance abuse in the history and/or at the time of screening (alcoholism - use of more than 30 ml of ethyl alcohol per day during the last 6 months; drug dependence - use of any narcotic substances in any doses during the last 6 months; substance abuse - use of any psychoactive substances in any doses during the last 6 months). 34. History of schizophrenia, schizoaffective disorder, bipolar disorder. 35. Tuberculosis, hepatitis B and C, HIV infection, syphilis, history or by screening. 36. Conditions after surgical procedures, if less than 6 months have passed since the intervention. 37. Therapy for cognitive impairment, balance disorders, and dizziness 21 days or less prior to Visit 1-1 date. 38. Use of an irreversible MAO inhibitor within 14 days or a reversible MAO inhibitor within 1 day prior to Visit 1-1. 39. Therapy with the following drugs and drug groups: 7 days or less before screening: Selective serotonin reuptake inhibitors (SSRIs) and selective serotonin and norepinephrine reuptake inhibitors (SSRIs); Cinnarizine and/or dimenhydrinate preparations; Cytochrome P450 3A4 (Cytochrome P450 3A4, CYP3A4) inhibitors and inducers: Erythromycin, itraconazole, nefazodone, diltiazem, verapamil, etc.; Cimetidine, warfarin, phenytoin, propranolol. Monoamine oxidase inhibitors (MAOIs): concomitant use of MAO inhibitors is prohibited, as well as taking the drug earlier than 14 days after withdrawal of an irreversible MAO inhibitor, or less than 1 day after withdrawal of a reversible MAO inhibitor. 40. Presence of a history of malignant neoplasm, except in patients who have had no disease in the past 5 years, patients with completely cured basal cell skin canc