SNPs: Single Nucleotide Polymorphisms and Pharmacogenomics: Individually Designed Drug Therapy

Pharmacogenomics is a rapidly expanding field aimed at understanding interpatient variability in drug response through the exploration and investigation of the human genome. It is an incontrovertible fact that large interpatient variability exists in response to medications. Variation in response has existed as long as medications have been used for the prevention and treatment of disease. In many ways, the field of pharmacogenomics began serendipitously in the 1950s after seminal observations describing variability in response to medications. Examples included peripheral neuropathy from isoniazid among slow acetylator, prolonged apnea from succinylcholine caused by pseudocholinesterase deficiency, and severe hypotension from debrisoquine among cytochrome P450 (CYP) 2D6 poor metabolizers. For the next 40 years, pharmacogenetic studies focused almost exclusively on the etiologies of altered variability in pharmacokinetic responses to medications. As we entered the 1990s, pharmacogenomic studies began to include studies that examined pharmacodynamic variability in drug response. Now instead of examining only differences in drug metabolizing enzymes, scientists began to focus on genes that encode drug transporters, drug targets, and ion channels. The ultimate goal of pharmacogenomics is to be able to accurately predict, based on an individual’s genomic information, which medications will provide the greatest benefit with the least harm, thus transforming medicine into an era of personalized therapeutics. This chapter provides a review of pharmacogenomics and how single nucleotide polymorphisms may impact pharmacotherapy and drug discovery. The chapter further explores the abundant recent literature as well as provides insight into some of the issues, limitations, and ethical considerations of pharmacogenomics. Keywords: pharmacogenomics; pharmacogenetics; single nucleotide polymorphisms; SNPs; individualized pharmacotherapy