Therapeutic Drug Monitoring in Psychiatry – Genotyping amends clinical pharmacological comments

In our laboratory we quantify serum concentrations of various drugs that are frequently used in psychiatric therapy. The values are returned together with a clinical pharmacological comment that relates the serum concentration to the dose given to the individual patient. Thereby a signal is created that allows to identify individual peculiarities such as drug interactions, compliance under question, and genetically determined metabolic polymorphism. We now proceed to analyse the genetic expression of metabolizing enzymes in the latter population (genotyping). Our methodological approach searches for methods which may be simply integrated in our regular laboratory routine. Since PCR meets most of these requirements, we so far established methods for CYP 1A2 (C164A) and for CYP 2C19, that were taken from literature; methods for CYP 2C9 *2 and *3 were modified concerning annealing temperature and magnesium chloride concentration. Furthermore, the expression of CYP 2D6 and CYP 3A4 will be addressed as well. In a particularly designed study we want to compare the clinically relevant information obtained by genotyping to phenotyping by therapeutic drug monitoring.