Individualized treatment decisions in psychiatry may be important, since substantial part of first choice drugs are ineffective or cause side effects. Polymorphic variants of genes that code CYP450 enzymes cause differences in their activity and therefore in efficacy and safety of drugs that are metabolized by them.

Determine whether pharmacogenetic testing of CYP2D6, CYP2C19 and CYP2C9 polymorphism would have had influence on selected patients’ treatment courses.

Five patients that were diagnosed for treament-resistant mood disorders in Vilnius university hospital Santariskiu clinics centre of neurology, department of psychiatry were invited to give blood samples for genetic testing retrospectively. Patients’ CYP2C19, CYP2D6 and CYP2C9 enzymes genetic polymorphism results were compared with previous empirical pharmacological treatment courses of these patients.

In four out of five cases significant polymorphism of CYP2C19 enzyme allele was detected. In all of these cases 1*/2* variant, that conditions intermediate metabolizer phenotype, was identified. Alterations in CYP2D6 and CYP2C19 regions were not found. In three cases the presence of varied genetic variant could have been clinically relevant. In two of these cases Sertraline and valproates, that are both metabolized by CYP2C19 enzyme, were taken by patients and side effects were observed. Unsuccessful treatment was repeated without effect, both in clinical and outpatient environment. Continuous rehospitalization took place until appropriate empirical treatments were established.

Pharmacogenetic testing could have had influence on treatment choices for three out of five selected patients leading to less side effects and rehospitalizations.

The authors have not supplied their declaration of competing interest.