Backgroun and aims: Pharmacokinetic variability is of paramount importance for sucessfull pharmacotherapy. The main purpose of this work was to study variability of pharmacokinetics in clinical and non-clinical setting with the aim to predict variability in target population. Specifically, three drugs were chosen, sufentanil, with relativelly narrow therapeutic index, and nabumeton and abirateron, both with known high variability. Methods: The study of pharmacokinetic variability of sufentanil was based on clinical samples taken from patients undergoing surgical cardiac procedure, where the sufentanil was used as a part of the drug coctail used during the procedure. New analytical method was necessary to prepare and validate to measure sufentanil concentrations and obtain pharmacokinetic parameters. These were compared between determined genotype groups of MDR1 and OPRM1. Similarly, clinical study was executed with nabumetone, in which nabumetone was administered in a group of 24 subjects on two separate occassions. Plazma samples were obtained and concentrations of nabumetone and its active metabolite, 6-methoxynaphtylacetic acid (6-MNA), were determined. Obtained pharmacokinetic profiles were compared between female and male volunteers, and genotypes for MDR1 and CYP2D6. Finaly for abiraterone,...