Many people find a medication plan that works for them by testing out different medications or dosages, each varying in effectiveness and possibly resulting in negative side effects. This process can be time-consuming and often frustrating. In recent years, many healthcare providers have begun using genetic testing to improve the process of prescribing medication. This type of testing is called pharmacogenomic testing.
What is pharmacogenomics?
Pharmacogenomics (PGx), or pharmacogenetics, is the study of how a person’s genes influence their response to various drugs.
Your body metabolizes, or breaks down, medication over time. This process happens mostly in the liver, with molecules called enzymes. Just six enzymes are responsible for metabolizing more than 90% of all psychiatric medications . Your DNA contains genes that tell your body how to make these enzymes.
Each of these genes has variations that lead to differences in the way enzymes are structured and how they work.
Just as differences in genes can lead to one person being blonde and another having red hair, differences in this set of genes can lead to two people processing the same medication in different ways.
What does a pharmacogenomics test do?
A PGx test looks at your DNA to see which version of each gene you have. The test is provided by your doctor or through the mail. It involves either spitting into a vial or swabbing your cheek, then sending the sample to a lab for analysis.
Scientists often assign each gene variation to one of three groups: rapid metabolizer, slow metabolizer, or extensive metabolizer. These different groups correspond to whether your variation of a particular enzyme can break down a substance quickly, slowly, or at an average rate, respectively. Knowing what kind of genetic variations you have gives your medical provider insight into how your body breaks down drugs.
Psychiatrists and other doctors have been increasingly using PGx testing in mental health treatment because it’s shown to reduce the risk of side effects, decrease medication switching, and, most importantly, increase the chance that patients get better.
How do PGx test results affect my prescription?
PGx tests tell your medical provider how your genes differ from others—and how these differences affect your metabolism. Your PGx test tells you what version of each gene you have. It then provides a list of medications that will work best with the enzyme encoded by that gene. This list might also come with some recommendations.
For example, having a certain genetic variation might result in you having a slow metabolizer enzyme variant. Because this type of enzyme breaks down medication more slowly than average, a certain drug may stay in your system longer than usual. This can lead to negative side effects. A PGx test might recommend that your provider not prescribe this medication—or at least lower the dosage to prevent side effects. Without a PGx test, you would only find this out by trial and error.
What do scientists know about PGx testing?
While pharmacogenomics may be an unfamiliar term to many, it dates back to the 1950s. Since then, researchers have gained a greater and greater understanding of how specific genes impact the way we respond to different medications. Studies have shown that PGx testing can reduce the burden of side effects for people with major depressive disorder  and improve outcomes in those with anxiety and depression . The FDA now recognizes the value of PGx tests , stating that they can be helpful in creating a prescription plan.
However, there is currently not enough knowledge on the relationship between genes and medication to definitively say which medication is right for you and at which dosage. While genetics is a major factor, other things affect the way you respond to medications. PGx tests can only provide recommendations and suggestions regarding various medications to reduce the trial-and-error approach. Instead of providing an answer, PGx tests provide a starting point to help you and your provider make the right decision about which medication is appropriate and in what amount.
PGx testing has the potential to shorten the trial-and-error period and help people more quickly find a plan that fits. If you’re wondering whether you are likely to benefit from pharmacogenetic testing, you can take a free pharmacogenomics quiz that’s backed by the latest scientific research.
- Lynch & Price. (2007). The Effect of Cytochrome P450 Metabolism on Drug Response, Interactions, and Adverse Effects. American Family Physician 76(3), pp. 391-396. Retrieved from https://www.aafp.org/afp/2007/0801/p391.html
- Pérez et al. (2017). Efficacy of prospective pharmacogenetic testing in the treatment of major depressive disorder: results of a randomized, double-blind clinical trial. BMC Psychiatry 17, p 250. Retrieved from https://doi.org/10.1186/s12888-017-1412-1
- Bradley et al. (2017). Improved efficacy with targeted pharmacogenetic-guided treatment of patients with depression and anxiety: A randomized clinical trial demonstrating clinical utility. Journal of Psychiatric Research 96, pp. 100-107. Retrieved from https://doi.org/10.1016/j.jpsychires.2017.09.024
- S. Food and Drug Administration. (2020). Table of Pharmacogenetic Associations. Retrieved from https://www.fda.gov/medical-devices/precision-medicine/table-pharmacogenetic-associations