Chronic pain syndrome is a disease characterized by persistent, poorly treatable pain syndrome lasting more than 6 months. Such pain syndrome in most cases is the result of somatic disease or trauma. The main cause of chronic pain syndrome is long-term persistent pain, which causes an imbalance in the peripheral and central nervous system. Neuronal receptors and fibers in this case are subjected to constant activation, which leads to increased stimulation of the central nervous system (spinal cord and brain) by pain stimuli. One of the main causes of chronic pain is the appearance of complexes of hyperreactive neurons at various levels of the CNS. Their pathologic activity is caused by the breakdown of neuronal inhibition mechanisms, increased excitability of neurons and activation of inactive synapses, which unites these neurons into a single focus of excitation with self-sustained ectopic activity. This activity leads to functional, structural, and adaptive (neuroplastic) changes in the brain and spinal cord, causing pain to persist even when its cause is eliminated. There are many medications currently used to treat chronic pain, one of which is the widely used mirtazapine.