by Leah Samera, PharmD Candidate, Class of 2018
As with most things, when it comes selecting a drug regimen for the treatment of chronic disease, one size does not fit all. If you take medications, you may have wondered why that is the case. One reason is because of pharmacogenomics.
Pharmacogenomics refers to “the entire spectrum of genes that interact to determine drug efficacy and safety.” In practice, many people may use the terms pharmacogenomics and pharmacogenetics interchangeably.
Pharmacogenetics, however, also refers to variants of one gene that affect drug response. The study of both pharmacogenomics and pharmacogenetics can help to optimize drug therapy and minimize drug toxicity based on an individual’s genetic profile.
What is a gene?
A gene is a series of codons that specify a particular protein. Genetic variation may result in altered protein sequence and function or in altered protein levels. This is significant, because these proteins can have an effect on how your body interacts with medications.
How do pharmacogenomic variations affect drug response?
The impact of pharmacogenomic variations on drug response have traditionally been divided into four categories:
- Those that affect drug pharmacokinetics. Pharmacokinetics refers to how a medication moves through a person’s body, i.e., how the drug is absorbed, distributed, metabolized, and eliminated. An example of a genetic variation that affects pharmacokinetics is one in which drug metabolism is altered, subsequently affecting plasma concentration.
- Those that effect on pharmacodynamics. Pharmacodynamics refers to a person’s therapeutic response to a medication; this depends on a medication’s affinity and activity at its site of action. An example of a genetic variation that affects pharmacodynamics is one in which binding of a drug to its receptor is reduced, thereby decreasing therapeutic efficacy.
- Those that affect idiosyncratic reactions. An idiosyncratic reaction is an adverse reaction to a medication that is both rare and unpredictable. An example of a genetic variation that affects idiosyncratic reactions is one in which the likelihood of a hypersensitivity reaction to a certain drug is increased.
- Those that affect disease pathogenesis or severity and response to specific therapies. Pathogenesis refers to the origination and development of a disease. An example of a genetic variation that affects pathogenesis is a specific molecular defect related to the development of certain malignancies for which there are targeted therapies.
How can the study of pharmacogenomics help to optimize your drug therapy and minimize side effects?
Organizations like 23andMe allow people to “access, understand, and benefit” from the study of pharmacogenomics. With their simple home-based saliva collection kits, all you have to do is order their Health + Ancestry service; register, and spit into, the provided tube; and mail the kit back to their lab via the pre-paid package. Next, their lab extracts, processes, and analyzes the DNA from the cells in your saliva. Within 6 to 8 weeks, you get an email notifying you that you can view your results in your online account and discover what your DNA says about you. By sharing those results with your healthcare providers, they then can use that information to ensure that you get the most benefit from your medications while minimizing the risk of side effects.
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