Asthenic syndrome is a non‑specific syndrome that is often found in general medical practice in patients with various somatic pathologies both during an exacerbation of a chronic disease, and after an acute process. The leading symptoms in the clinic of asthenia are pathological weakness and fatigue. According to various researchers, they are found in 15–45 % of people. To date, there is no universally accepted definition and clear classification of this syndrome. The main pathogenetic concepts are the psychosocial, infectious‑immune theory of asthenia. The development of asthenic syndrome in patients with somatic pathology may be associated with the depletion of the functional capabilities of the nervous system due to disturbances in the blood supply to the brain, auto‑toxicity or exposure to exogenous toxic factors in bacterial, viral infections. There is no specific treatment for this condition. This article presents two clinical cases of the development of post‑infection asthenic syndrome in a 47‑year‑old patient against community‑acquired pneumonia and in a 36‑year‑old patient after an acute respiratory‑viral infection of moderate severity. In both cases, drug treatment with Mildronate was carried out with a positive trend in the form of regression of asthenia symptoms, side effects during treatment. Mildronate belongs to the class of cytoprotectors – antihypoxants, activates glycolysis and prevents impaired transport of adenosine triphosphate, providing a sufficient level of energy synthesis, which allows cells to maintain homeostasis and morphological integrity. The immunoadjuvant properties of Mildronate are very important in post‑infectious asthenic syndrome, since a violation of the immune response plays a central role in its pathogenesis. The immunoadjuvant properties of Mildronate have been discovered in a number of studies.