Pharmacogenomics: Drugs and Genetics?

Ever wonder if who your genetics determines how drugs affect you? Well guess what, there's a whole scientific field dedicated to researching how our genetic make-up affects the medications we take. It's called pharmacogenomics.

Everyone is made up of a unique, complex combination of genes. These genes give us are variations in appearance, but it also gives us variations in how we respond to drugs. And it's not just prescription drugs, but also to recreational drugs (such as marijuana), over-the-counter drugs, and even herbal supplements. A medication for one person may work very well and be beneficial, but it may not work at all for someone else, or worse, it may cause an undesirable side effect (adverse drug event).

Has it been a while since that genetics class? Maybe you're interested in a brief Genetics 101 overview provided by the Centers for Disease Control and Prevention (CDC).

What is pharmacogenomics?
  • Pharmacogenomics (also known as pharmacogenetics and drug-gene testing) is the study of how genes affect the body's response to medications. Pharmacogenomics combines the field of pharmacology (the study of medications) and genomics (the study of genes). This field of research is aimed to help healthcare providers choose the right drug in the right dose best suited for each particular person.
  • Every person has thousands of genes that have been inherited from generation to generation. These genes are responsible for physical characteristics such as hair color, eye color, and blood type, but are also responsible for how medications are processed in the body. By analyzing the genes specific to drug metabolism doctors may determine whether a medication could be an effective treatment before a person ever takes it.

How does pharmacogenomics affect medicine?
  • Genes are the instructions of the human body. They determine how the body looks and how the body works. These genes are made up of DNA and each person can have different compositions of DNA that make up a gene, making each individual unique.
  • Pharmacogenomics focuses on the differences in genes that are responsible for how medications are processed. Certain proteins in these genes have a big influence on a person's response to drugs. They can be responsible for converting medications into their active or inactive form. This is a concern when looking at drug safety and efficacy.
What role does pharmacogenomics play in healthcare?
  • Routine pharmacogenomic testing is becoming common only in a few diseases, but pharmacogenomics is expected to grow rapidly in the years to come. The field has been studying the effect of drugs used for heart disease, cancer, asthma, depression, and more. Some examples of where pharmacogenomics have proven useful are listed below:
Conditions
  • Acute Lymphoblastic Leukemia – Before giving a patient the chemotherapy medication mercaptopurine (Purinethol), it is recommended to get a pharmacogenomic test to check for genes that may interfere with the body's ability to process the drug.1
  • Breast Cancer – A pharmacogenomic test is ordered to check for particular genes prior to starting the breast cancer medication trastuzumab (Herceptin).2
  • Colon Cancer – To lower the risk of diarrhea and infection, patients should be tested for certain genetic variants before starting the medication irinotecan (Camptosar)3
  • Human Immunodeficiency Virus (HIV) – Before a patient is prescribed the medication abacavir (Ziagen), a pharmacogenomic test is ordered. The test is to check for a genetic variation that may cause the patient to be more likely to have a bad reaction to the medication.4
  • Pain – Pharmacogenomic testing can check for genetic variation of a liver enzyme responsible for the processing of many painkiller medications, such as codeine and morphine.5
  • Antiplatelet/Anticoagulant – Pharmacogenomic testing can help doctors decide which antiplatelet/anticoagulant medication is preferred for a patient and help decide the appropriate dose as well.
  • And many more... Check out the U.S. Food and Drug Administration (FDA) website for a more comprehensive list.


What is an adverse drug event (ADE)?
  • Drugs or medications can cause injury and/or illness even if taken properly. Many of these adverse drug events can occur because of the way the body processes the medication. It is estimated that 3 out of 4 ADEs are related to the amount of medication that is received, whether too little or too much. This can happen when a person's body cannot process the medication as intended, so it builds up and may become toxic. Or it can happen when a person's body processes the medication too quickly, and the person does not receive the maximum benefits of the medication. Using pharmacogenomic testing can help better tailor a person's medication to account for this genetic variation.
How is a pharmacogenomic test performed?
  • Depending on the site and service, pharmacogenomic tests can be performed using a small blood or saliva sample. In most cases, a simple mouth swab is all that is needed. It may take a few days to about two weeks for pharmacogenomic testing to be completed.
What are some common genes that are tested?
  • Many cytochrome P450 (CYP) enzymes are responsible for the metabolism of medications. Three commons enzymes are CYP2D6, CYP2C9, and CYP2C19. These enzymes are responsible for processing medications such as hydrocodone, ibuprofen, and diazepam respectively.
Pharmacogenomics is a relatively new field that offers many benefits in medication therapy. As technology and healthcare progresses, be sure to look out for more potential benefits of pharmacogenomic tests. Do you have questions or are you interested in pharmacogenomic testing? Talk to your primary care provider or pharmacist about the appropriateness and benefits getting tested.


References

  1. Cheok, Meyling H. et al. "Pharmacogenetics in Acute Lymphoblastic Leukemia." Seminars in hematology 46.1 (2009): 39–51. PMC. Web. 27 June 2017.
  2. Westbrook, Kelly, and Vered Stearns. "Pharmacogenomics of Breast Cancer Therapy: An Update." Pharmacology & therapeutics 139.1 (2013): 1–11. PMC. Web. 27 June 2017.
  3. Marsh, Sharon, and Janelle M Hoskins. "Irinotecan Pharmacogenomics." Pharmacogenomics 11.7 (2010): 1003–1010. PMC. Web. 27 June 2017.
  4. Department of Health and Human Services; Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. Available at http://aidsinfo.nih.gov/contentfiles/lvguidelines/AdultandAdolescentGL.pdf.
  5. Ting, Sonya, and Stephan Schug. "The Pharmacogenomics of Pain Management: Prospects for Personalized Medicine." Journal of Pain Research 9 (2016): 49–56. PMC. Web. 27 June 2017.
  6. Beitelshees, Amber L, Deepak Voora, and Joshua P Lewis. "Personalized Antiplatelet and Anticoagulation Therapy: Applications and Significance of Pharmacogenomics." Pharmacogenomics and Personalized Medicine 8 (2015): 43–61. PMC. Web. 27 June 2017.
  7. "What is pharmacogenomics? - Genetics Home Reference." U.S. National Library of Medicine. National Institutes of Health, n.d. Web. 10 June 2017.
  8. "Genetics Basics." Centers for Disease Control and Prevention. Centers for Disease Control and Prevention, 03 Mar. 2015. Web. 10 June 2017.
  9. "FAQ About Pharmacogenomics." National Human Genome Research Institute (NHGRI). N.p., n.d. Web. 10 June 2017.
  10. Center for Drug Evaluation and Research. "Genomics - Table of Pharmacogenomic Biomarkers in Drug Labeling." U S Food and Drug Administration Home Page. Center for Drug Evaluation and Research, n.d. Web. 10 June 2017.
  11. "Pharmacogenomics Fact Sheet." National Institute of General Medical Sciences. U.S. Department of Health and Human Services, n.d. Web. 10 June 2017.
  12. "Personalized medicine and pharmacogenomics." Mayo Clinic. Mayo Foundation for Medical Education and Research, 05 June 2015. Web. 10 June 2017.
  13. "Drug-Gene Testing." Drug-Gene Testing (Pharmacogenomics) - Mayo Clinic Center for Individualized Medicine. N.p., n.d. Web. 10 June 2017.