Pharmacogenomics

Pharmacogenomics is the study of how genetic variation influences an individual's response to medications. It seeks to explain differences in drug efficacy and the risk of adverse reactions by linking genetic variants to pharmacokinetics and pharmacodynamics. By identifying alleles that affect drug metabolism, transport, targets, or immune response, pharmacogenomics aims to guide drug selection and dosing to improve safety and effectiveness as part of precision medicine.

Genetic variation relevant to drug response includes single nucleotide polymorphisms, copy number variants, and other structural differences. Common examples include variants in drug-metabolizing enzymes such as CYP2C9 and CYP2D6, which alter drug clearance, and TPMT, which affects immunosuppressant toxicity. Immune-related adverse reactions can be predicted by HLA alleles, such as HLA-B*1502 with carbamazepine-associated Stevens–Johnson syndrome in certain populations or HLA-B*57:01 with abacavir hypersensitivity. Therapeutic recommendations are provided by guidelines from CPIC and the DPWG, and are increasingly incorporated into dosing algorithms (for example, warfarin dosing informed by VKORC1 and CYP2C9 variants).

Clinical use spans oncology, cardiovascular disease, psychiatry, and infectious disease. Evidence supports genotype-guided dosing or drug choice in specific circumstances, and regulatory labeling often includes pharmacogenomic information. Implementation faces challenges such as cost, testing access, and interpreting polygenic and context-dependent effects. Ethical and privacy considerations accompany genetic data use. Looking forward, integration with electronic health records, routine genotyping, and large-scale biobanks may expand the clinical utility of pharmacogenomics.