PGx: A Branch of Precision Medicine

In the new era of precision medicine, you may have heard the term “pharmacogenomics.” What is pharmacogenomics? Pharmacogenomics is a branch of precision medicine that looks at how genetic variants in DNA can affect how a patient may respond to medications. Human DNA is not identical and small differences in genes can affect how people process medications. These differences in DNA (genetic variants) are common and affect a large majority of the population as shown in the Mayo Clinic RIGHT study and Vanderbilt Predict study. Pharmacogenomics may affect how a patient metabolizes certain medications via the cytochrome p450 genes, how a certain medication is processed by the body through drug transport proteins or receptors or an adverse event gene such as the HLA genes. 

Pharmacogenomics, also known as PGx, has been around for a couple of decades but has been slow in making its presence in routine clinical practice. Barriers, such as interpreting genetic lab tests into clinical actionability, have been one of the obstacles causing this inertia. Part of this stems from the lack of education that physicians receive on PGx in medical school and residency. Although much evidence exists for PGx, it has not reached many practicing physicians/prescribers. Over 300 medications have PGx information in their FDA (Food and Drug Administration) labeling. In 2020 the FDA released, The Table of Pharmacogenetic Associations to list the medications that have PGx evidence.

Professional guidelines for PGx exist from the Clinical Pharmacogenetics Implementation Consortium also known as CPIC, which is an academic group that writes evidence based, peer reviewed guidelines for PGx to be used in patient care.  CPIC’s goal is to help in the clinical implementation of PGx by writing guidelines with therapeutics recommendations with considerations of medication and/or dosing changes.

PGx is a tool that physicians can use to aid in their therapeutic decision strategy. It can help select the medication and dosing to optimize the prescription with the patient’s genetic profile. It may also help the physician in assessing the likelihood of benefit or toxicity. Not all medications have PGx implications, and some patients may be excluded for testing such as those that have had a liver or bone marrow transplant. PGx has been shown to have clinical utility in therapeutic areas such as: Mental Health (depression and anxiety), Oncology (chemotoxicity and supportive care), Cardiology, Pain Management and Polypharmacy. 

If you would like more information regarding pharmacogenomics (PGx) please see these resources:

Julie Ceno-England, MD is a board-certified family medicine physician with more than 15 years of clinical practice experience. Dr England is currently the Senior Medical Director and VP of Medical Affairs at OneOme LLC, a med tech company located in Minneapolis, MN.