Schizophrenia is a common and socially significant mental disorder that requires long-term use of antipsychotics (APs). Long-term use of APs increases the risk of developing adverse drug reactions (ADRs) and/or therapeutic resistance in some patients. This may be due to a genetically determined impairment of APs metabolism by cytochrome P450 enzymes and of Aps transport across the blood-brain barrier (BBB) and the cell membrane of APs target neurons in the brain. Pharmacogenetic testing (PGx) is a method to identify a group of patients with a high risk of developing AP-induced ADRs. The aim of the case report is to present the experience of using PGx in a 36-year-old patient with treatment-resistant schizophrenia and a medical history of AP-induced ADRs.