Impact of the CYP2D6 phenotype on hyperprolactinemia development as an adverse event of treatment with atypical antipsychotic agents in pediatric patients

Background Treatment with atypical antipsychotics is today the election therapy for different types of psychosis, but there is a high incidence of endocrine and metabolic disturbances. One of the major enzymes involved in the metabolism of antipsychotics is CYP2D6. Depending on the existing CYP2D6 alleles, the metabolic capacity of the enzyme may vary from very low to very high, so that patients can be grouped into four phenotypic groups: slow, intermediate, extensive (normal), and fast metabolizers. Aim of the study The aim of the study is to find a relationship between the individual intervariability of CYP2D6 and the incidence of hyperprolactinemia as side effect of atypical antipsychotics. Results A total of 81 patients with schizophrenia or bipolar disorders, median age 15.74 ± 4 years, were enrolled in the study and prescribed the following atypical antipsychotics: risperidone, aripiprazole, and olanzapine. They were evaluated at 6, 12, and 18 months after the initiation of treatment. Using the TaqMan Genotyping Assay, it has been identified the presence of the CYP2D6*4 allele in 28 patients, representing 34.56% of the total of 81 patients in the study, and CYP2D6*3 allele was identified in 15 patients and the presence of CYP2D6*41 to 11 patients. The allele CYP2D6*5 has not been present to the study patients. The study group has 44 patients which are extensive metabolizers (54%), 34 intermediate metabolizers (42%), and 3 poor (slow) metabolizers (4%). Conclusions For the slow and intermediate metabolizers, atypical antipsychotics determined a significant increase of prolactinemia with high risk of adverse events.