The above recommendations were followed by a publication from the Royal Dutch Association for the Advancement of Pharmacy. The Pharmacogenetic Working Group (PWG), established by this association, developed guidelines that are available on the Pharmacogenomics Knowledgebase (PharmGKB) Web site (www.pharmgkb.org).21 The PWG publication includes 85 genotype and phenotype drug combinations for 25 medications. At this time, the drug-gene recommendations included on the PharmGKB site provide information for 17 psychiatric drugs as they relate to variants in the CYP2D6 gene. The number of guidelines for the CYP2C19 gene and neuropsychiatric medications is significantly lower (only one guideline). The PWG guidelines translate the phenotype and genotype information into therapeutic dose recommendations. In addition, information about clinical relevance is provided with the clearly stated level of the evidence (e.g., strong, moderate, and optional). PWG recommendations are designed to inform clinicians about dosage adjustments or drug choices in situations when genetic results are available.
