Due to their involvement in the metabolization of commonly prescribed psychopharmaceutical drugs, the cytochrome oxidase genes CYP2D6 and CYP2C19 are extensive targets for pharmacogenetic testing. The existence of common allelic variants allows the prediction of a metabolic phenotype based on a genotype result, hereby supplying a clinical tool for optimizing prescription and minimizing adverse effects. In this study, we present the development of two 5′ nuclease real-time polymerase chain reaction (PCR) test panels, capable of detecting eight of the most clinically relevant alleles of the CYP2D6 gene (*2, *3, *4, *6, *9, *10, 17, *41) and the three most common nonfunctional alleles of CYP2C19 (*2, *3, *4). The assays have been thoroughly validated using a large collection of reference samples, by parallel testing and by DNA sequencing. The reanalysis of reference samples provided the calculation of the frequency of the CYP2D6*4K allele in a population, not previously reported. Furthermore, original test results from CYP2D6*41, generated based on the presence of the 2850T and the lack of the −1584G single-nucleotide polymorphism (SNP), were compared with genotyping based on the current acknowledged founder SNP 2988G of this allele. These results indicate that up to 17.7% of the patients originally tested as carriers of the CYP2D6*41 allele may have had an incorrect phenotypic result assigned. The two 5′ nuclease real-time PCR test panels have subsequently been optimized for use in the clinical laboratory, using a standard real-time PCR instrument and software.

Background: The indication for the antiepileptic drug (AED) lacosamide (LCM) was recently extended to include children from the age of four. Real-life data on the use and serum concentrations of LCM in children and adolescents are limited. The purpose of this study was to investigate the use of LCM in this patient group in relation to age, comedication, dose, serum concentrations and duration of treatment, and to examine pharmacokinetic variability. Methods: Children and adolescents (<18 years) who had serum concentrations of LCM measured from January 2012 to June 2018 were retrospectively identified from the therapeutic drug monitoring (TDM) databases at two national epilepsy centers in Norway and Denmark. Clinical data were collected from request forms and medical records. Results: Data from 124 patients were included, 61 girls/63 boys. Weight was available for 76 patients. Median age was 15 years (range 2-17 years), dose of LCM 300 mg/day (76-600 mg/day) and serum concentration 18 µmol/L (5-138 µmol/L) [4.5 mg/L (1.3-34.5 mg/L)].

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