Pharmacogenomics, PGx, Overview includes selected milestones in the first 60-years of PGx, types and naming of genetically derived cytochrome P450 or CYP hepatic drug metabolizing enzymes, DNA single nucleotide polymorphisms or SNPs (“snips”) resulting in CYP phenotypes that cause from excessively fast to normal to excessively slow to absent drug metabolism, and clinical examples of   the effects on psychiatric and other drugs from CYP phenotypes, and inducers and inhibitors of particular CYPs.