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Pharmacogenomic Testing

Pharmacogenomics is the study of how a person’s genes impact their reaction to drugs. It is a relatively new field that holds promise for choosing the most effective medications and dosages with the least likelihood of side-effects based on a person’s genetic makeup.

Doctors can use these tests to inform decisions about what kind of anesthesia is safest to use and to select the best treatment options for cancer, heart disease, neurological problems, infectious diseases, and some mental health conditions like depression.[i] By analyzing the genetic variations in your DNA, the test can provide information about genes that may impact how you break down or react to certain medications.

When it comes to depression, a pharmacogenomic test will look at two main factors in your genes.

  • Pharmacodynamic factors. Pharmacodynamic factors are genetic variations that indicate how a medicine will affect your body. Depending on who makes the test, a test may look for variations in one, or up to four different genes.
    • The SLC6A4 gene determines how many serotonin transporters you have. If you have a low number of transporters, it is less likely that a group of medications called SSRIs (selective serotonin reuptake inhibitors) will be effective for you.
    • A variation in the 5HTR2A gene indicates a higher likelihood that you will experience side effects from certain medications.
    • Variations in the HLA-B*1502 and HLA-A*3101 genes have to do with your immune system and the likelihood that you will have skin reactions from certain drugs. One particular type of skin reaction called Stevens-Johnson syndrome is serious and can be fatal.
       
  • Pharmacokinetic factors. Pharmacokinetic factors have to do with what your body will do to medication. This includes the presence of certain enzymes in your liver that breakdown medications. Because everyone is different, some people will break down medications more quickly or more slowly than others. People who break down medications more slowly have an increased risk of side effects and may need lower doses of medication, while people who break down medications more quickly may need higher doses of medication or medications that have a longer half-life.

Pharmacogenomic tests, unlike genetic tests (Ancestry, 23andMe, etc.) must be ordered by a medical professional and are done at a doctor’s office with a quick and painless cheek swab. Most health professionals will not order a pharmacogenomic test before putting you on your first medication for depression. This tool is more likely to be used after you have tried one or more medications that have not given you relief for depression or have caused side effects that are too disruptive to warrant continued use of a certain drug. Multiple studies have found that people whose treatment providers selected medications based on a certain pharmacogenomic test had improvement in depression symptoms based on the Hamilton Rating Scale for Depression (HAM-D17).[ii]

If you struggle with depression that has not responded to one or more medications, it is worth mentioning pharmacogenetic testing to your treatment provider at your next appointment so they can make more informed decisions about which treatments to try moving forward. Be sure to contact your insurance company to see if this type of test is covered by your plan, and what (if any) costs you may have to pay out-of-pocket if a test is done.


[i] https://www.fda.gov/drugs/science-and-research-drugs/table-pharmacogenomic-biomarkers-drug-labeling

[ii] https://genesight.com/for-clinicians/