Evidence based drug dosing and pharmacotherapeutic recommendations per genotype.

Implementing pharmacogenetics in daily clinical practice has the potential to improve patient care. The translation of results of pharmacogenetic studies into practical pharmacotherapeutic recommendations is essential. These recommendations are preferably available at the time of drug prescribing and drug dispensing. This chapter describes a process of developing evidence based drug dosing and pharmacotherapeutic guidelines per genotype by the Dutch Pharmacogenetics Working Group. It is aimed to provide recommendations in case drugs are prescribed to a patient whose genotype is known. Furthermore, several examples are given. Many drugs are metabolized by the Cytochrome P450 CYP2D6 enzyme. Carriage of genetic variants of the CYP2D6 gene can result in a predicted phenotype of poor, intermediate or ultrarapid metabolizer. Dose adjustments, pharmacotherapeutic and monitoring recommendations are described for several CYP2D6 substrates, when initiated in patients with the above mentioned phenotypes.