Pharmacogenomics (PGx) is a component of personalized and precision medicine which utilizes a patient’s genetic information, along with other clinical factors, to help choose a medication. PGx information may help determine the doses of medications that are likely to work best for each person. The choice and dose of medications are often determined based on studies for what works, on average, for a large population. For an individual person, response to medication can differ widely. This is sometimes due to variation in their genes. These differences in genetic makeup can affect the safety and efficacy of medications. This information is then used to maximize the benefits of mediation while reducing the undesirable side effects.
TriHealth PGx Services provides pharmacogenomic testing and education to individuals.
Common situations when a pharmacogenomic test may be ordered:
With a pharmacogenomics approach, patients work with their physician, pharmacist, and genetic counselor to select medications, reduce adverse effects and/or treatment failure, and improve overall health outcomes.
There are two different types of PGx clinic visits: 1. Pre-test and 2. Post-test visits. A typical visit includes a pharmacist and genetic counselor reviewing a patient’s current and historical medications to determine if genetic testing may be helpful. The team also provides education about genetic testing and medications, helps to coordinate the genetic testing, and then reviews the results.
Who is a pharmacogenomics (PGx) pharmacist?
A PGx pharmacist is a pharmacist who specifically studies the interactions between medications and an individual person’s genes.
The PGx pharmacist reviews the genetic test results and combines the results with pertinent information gathered from the patient regarding their medical and medication therapy history. With the knowledge obtained from the genetic test results, patients who are at an increased risk of medication toxicity and/or at risk for poor or no response to medications are identified. After obtaining and reviewing the information needed, the pharmacist will discuss results with both the patient and care provider in order to optimize medication therapy.
Who is a pharmacogenomics (PGx) genetic counselor?
A PGx genetic counselor specializes in understanding and explaining how variations in an individual’s genes can affect the way they respond to medications. Genetic counselors are specially trained in human medical genetics and counseling.
The genetic counselor assists in educating patients on genes and drug metabolism in the pre-test setting and communicating the implications of PGx test results in the post-test setting. They also focus on risk to family members and can identify other relatives who may benefit from genetic testing.
Pharmacogenomics (PGx) testing:
Pharmacogenomics tests are available for several different medications. Testing can include one or two genes related to a specific medication of interest. This is called “disease or drug specific testing”. Testing can also cover a collection of genes that are related to a variety of medications. This type of testing is called “panel testing”.
| Medicine | Gene |
|---|---|
| Abacavir (Ziagen) | HLA-B*57:01 |
| Clopidogrel (Plavix) | CYP2C19 |
| Codeine | CYP2D6 |
| Citalopram (CeleXA) | CYP2C19 |
| Irinotecan | UGT1A1 |
| Tramadol (Ultram) | CYP2D6 |
| Venlafaxine (Effexor) | CYP2D6 |
| Voriconazole (Vfend) | CYP2C19 |
| Warfarin (Coumadin) | CYP2C9, VKORC1, CYP4F2 |
CYP2C19 testing:
Patients taking Clopidogrel (Plavix) for acute coronary artery disease (ACS), or those undergoing percutaneous coronary intervention (PCI), may benefit from CYP2C19 testing.
Why is genetic testing important for Clopidogrel (Plavix)?
Clopidogrel is an antiplatelet medication used to treat patients with ACS, particularly individuals undergoing PCI. Antiplatelet medications reduce the risk of blood clot formation in the body.
To be effective, clopidogrel must be converted to its active form through metabolism by an enzyme called CYP2C19. Genetic variations of CYP2C19 result in different responses to therapy. The loss of function of this enzyme is associated with having less active form of the medication in the body. Decreased antiplatelet activity means the medication would not work as it should. This can cause adverse effects in patients.
Based on the genetic results, your doctor may prescribe a different medication for you.
HLA-B*57:01 testing:
Abacavir is used along with other medications to treat human immunodeficiency virus (HIV) infection. Abacavir is in a class of medications called nucleoside reverse transcriptase inhibitors (NRTIs). It works by decreasing the amount of HIV in the blood.
Why is genetic testing important for Abacavir?
Some patients may be more likely to have a serious or life-threatening allergic reaction (hypersensitivity) to abacavir based on their genetic make-up. The HLA-B*57:01 genetic variant is strongly associated with hypersensitivity reactions to abacavir. Patients who are HLA-B*57:01 positive are at a much higher risk of experiencing allergic reactions and therefore, should not use abacavir. Instead, a different antiretroviral therapy can be prescribed.
Your doctor will order HLA-B testing to determine if you are more likely to have an allergic reaction to abacavir before starting treatment.
More comprehensive PGx panel testing may look at 10 or more genes. In a panel test, many different genetic changes can be identified on a single test. This is beneficial because one test can provide information about a wide variety of medications (cancer, cardiology, psychiatric and pain management therapies) or if a patient is taking multiple medications (polypharmacy).