Take Away Points Patients respond differently to therapeutic interventions based on genetic variations found across populations Genomic medicine has a potential role to reduce adverse drug reactions and improve medication efficacy With over 200 medications that are affected by genetic variations, the benefits of genomic medicine touch many different specialties and can have huge implications across healthcare What is Genomic Medicine? Genomic Medicine refers to a growing field of medicine that consists of using genomic information to influence medical decision making, clinical care, and how this affects health outcomes. An important component of this emerging field is the pharmacogenetics of medication. This is the study of how individuals respond differently to medications or drugs based on their genetic makeup. In a time where treatment guidelines are developed from focusing on entire populations with big data research, the idea that we may base clinical decision making from an individual’s genetic makeup seems out of place in the exam room. However, this is far from the truth. “According to a US Food and Drug Administration (FDA) report from 2013, an astounding 38–75% of patients who have a common disease do not respond to treatment” (Zhang et al 2019). In addressing these treatment failures, genomic medicine could have great implications on improving quality of life and decreasing the ever-growing cost of healthcare. Cytochrome P450 Genetic Variation and Prescribing Medications Cytochrome P450, a group of enzymes that are responsible for the metabolism of medications and expressed according to genotypes, may be a key player in decreasing adverse drug reactions. In understanding the way patients metabolize drugs differently, we may be able to predict reactions and avoid adverse events. For instance, the FDA has recommended that HLA testing be performed prior to initiating carbamazepine, given as a first line treatment for epilepsy. The HLA genotype is associated with an increased risk for Stevens Johnson Syndrome/Toxic Epidermal Necrolysis, as well as other adverse effects from carbamazepine (Dean, 2015). Another way genetic variation can affect clinical practice is when selecting antiplatelet medications. Researchers have discovered different CYP2C19 genotypes, and each genotype metabolizes clopidogrel at different speeds (Lynch, 2007). By understanding which genotype confers poor versus intermediate versus “normal” metabolization of clopidogrel, clinicians can predict which antiplatelet medication may be more or less effective. Drug selection may become more informed and subsequent outcomes may improve with this type of decision making. Furthermore, by using genetic variation to influence drug development and selection, adverse drug reactions, currently responsible for 7-14% of hospitalizations, may be decreased and avoided altogether (Center for Drug Evaluation and Research, 2018). From warfarin to fluoxetine, the FDA has identified over 200 medications that may be affected by genetic variation and may warrant genetic testing prior to initiation in the future (Center for Drug Evaluation and Research, 2020). It is not inconceivable to believe that genetic testing will be the norm prior to selecting any medication. Implications for the Future Drug selection just scratches the surface for the future of genomic medicine. No matter the specialty, genomic medicine is finding a foothold. The National Human Genome Research Institute is conducting research on how genetic variation can affect oncology, metabolic, cardiovascular, and infectious treatment plans (Accomplishments in Genomic Medicine, 2018). In allowing clinicians to predict outcomes based on objective information (our DNA), genomic medicine holds promise in improving therapeutic responses to treatments and increasing the efficacy and safety of our treatments. Interested in Learning More? NIH National Institute of General Medical Sciences – “Pharmacogenenomics” NIH U.S. Library of Medicine – “What is Pharmacogenomics?” NIH National Human Genome Research Institute – “Genomics and Medicine” FDA U.S. Food & Drug Administration – “Table of Pharmacogenomic Biomarkers in Drug Labeling” REFERENCES Accomplishments in Genomic Medicine. (2020, July 29). Retrieved September 01, 2020, from https://www.genome.gov/health/Genomics-and-Medicine/accomplishments Center for Drug Evaluation and Research. (2018, March 06). Preventable Adverse Drug Reactions: A Focus on Drug Interactions. Retrieved September 01, 2020, from https://www.fda.gov/drugs/drug-interactions-labeling/preventable-adverse-drug-reactions-focus-drug-interactions Center for Drug Evaluation and Research. (2020, August 18). Table of Pharmacogenomic Biomarkers. Retrieved September 01, 2020, from https://www.fda.gov/drugs/science-and-research-drugs/table-pharmacogenomic-biomarkers-drug-labeling Dean, L. (2015). Carbamazepine Therapy and HLA Genotype. Medical Genetics Summaries [Internet]. doi:https://www.ncbi.nlm.nih.gov/books/NBK321445/ Zhang, H., Klareskog, L., Matussek, A., Pfister, S. M., & Benson, M. (2019). Translating genomic medicine to the clinic: Challenges and opportunities. Genome Medicine, 11(1). doi:https://genomemedicine.biomedcentral.com/articles/10.1186/s13073-019-0622-1 Lynch T, Price A. (2007). The effect of cytochrome P450 metabolism on drug response, interactions, and adverse effect. American Fam Physician, 76(3):391-396.