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. Pharmacogenetic testing (PGx) is a method to identify a group of patients with a high risk of developing AP-induced ADRs. Our experience of using PGx to search for low-functional and non-functional single nucleotide variants (SNVs) / polymorphisms of the CYP1A2, CYP2C9, CYP3A4, CYP3A5 and CYP2D6) genes encoding cytochrome P450 enzymes involved in APs metabolism demonstrates the importance of this new personalized approach to the choice of APs and its dosing in patients with pharmacogenetic profile poor metabolizer. The main purpose of the case report is to present the experience of using PGx in a 28-year-old patient with treatment-resistant schizophrenia and a medical history of AP-induced ADRs.