The field of pharmacogenetics explores how DNA variants influence the body’s ability to process medications. “Pharmacogenetics” and “pharmacogenomics” are sometimes used interchangeably, but pharmacogenetics more often refers to genetic testing for variants in specific genes, while pharmacogenomics is used in the broader context of whole-genome sequencing or genetics-guided drug development.
Most pharmacogenetic variants are inherited, germline DNA differences that can impact pharmacokinetics (what the body does to the drug) or pharmacodynamics (what the drug does to the body). Pharmacokinetic effects include altering absorption, distribution, metabolism, and elimination, while pharmacodynamic effects may include altering the body’s sensitivity to a drug or altering the drug target itself. Many pharmacogenetic variants are found in genes that code for metabolizing enzymes, while other pharmacogenetic variants can affect proteins that transport medications, play a role in the immune system, or impact the clearance of a specific virus.
Depending on the medication, pharmacogenetic variants may reduce effectiveness, increase the chance of experiencing side effects, or have no effect. Researchers have determined that variants in approximately 20 genes may affect about 80 medications. More specifically, the Clinical Pharmacogenetics Implementation Consortium (CPIC®) has classified approximately 50 gene-drug pairs as having a high level of evidence and being actionable through dosing or medication changes.
It’s worth noting that not all pharmacogenetic variants are inherited; some are acquired DNA changes that are found only in cancer cells. Some oncologists may screen patients for these kinds of variants in order to help target cancer treatments more effectively.