Genes tested in pharmacogenetics
Genes serve as the instructions our bodies use to develop, grow and function throughout our life. In pharmacogenetics (PGx), genes are tested for their association with predicted medication response. Most genes analyzed in PGx testing provide instructions for enzymes. Enzymes are proteins in the body that help process medications by either activating them or breaking them down (metabolizing them). Genetic variations found in these genes can affect how quickly or slowly an individual processes a medication, influencing the medication’s effectiveness and potential side effects.
What is CYP2C9?
CYP2C9 is a gene that provides instructions to make the CYP2C9 enzyme, which is involved in the breakdown (metabolism) of medications within the body. This enzyme is mainly found in the liver, which is where it processes certain medications, affecting how well they work and how long they stay in the body.
PGx testing of CYP2C9
Genetic variation—the natural differences in DNA sequences between individuals—can affect how different people process the same medication. Because of specific genetic variation, the CYP2C9 enzyme may work differently from person to person.
The results of CYP2C9 PGx testing can predict how quickly or slowly your child is able to metabolize certain medications, which can help their health-care team choose or adjust their medication and dosage.
Medications affected by CYP2C9
Currently, there are many different medication classes and types that are affected by genetic variation in CYP2C9. If your child’s enzyme is predicted to work slower or faster than most individuals, it may affect how these medications work:
- Anticoagulants – medications that prevent blood clotting
- Statins – medications that help lower cholesterol
- Fluvastatin
- Fluvastatin
- Anticonvulsants – medications to help prevent seizures
- Fosphenytoin/phenytoin
- Fosphenytoin/phenytoin
- Nonsteroidal anti-inflammatory drugs (NSAIDs) – medications that help with pain and inflammation
- Celecoxib
- Flurbiprofen
- Ibuprofen
- Piroxicam
- Meloxicam
- Celecoxib
The medications listed above are referred to by their generic names. You may hear your child’s medication called by a different brand name. Generic medicines and brand-name medicines share the same active ingredient and offer the same performance, safety and effectiveness. This medication list is also subject to change with increasing research on the CYP2C9 enzyme.
CYP2C9 metabolizer statuses
The PGx results for CYP2C9 are organized into metabolizer status categories, based on the predicted function of the enzyme. Patients may be categorized into one of three groups:
- Poor metabolizer – reduced enzyme activity; your child may break down medication significantly slower than most individuals
- Your child’s health-care team may recommend starting with a lower dose of medication or switching to a different medication to ensure it works safely and effectively for your child.
- Your child’s health-care team may recommend starting with a lower dose of medication or switching to a different medication to ensure it works safely and effectively for your child.
- Intermediate metabolizer – reduced enzyme activity; your child may break down medication slower than most individuals
- Your child’s health-care team may recommend starting with a lower dose or maintaining a reduced dose to help ensure the medication works safely and effectively for your child.
- Your child’s health-care team may recommend starting with a lower dose or maintaining a reduced dose to help ensure the medication works safely and effectively for your child.
- Normal metabolizer – average enzyme activity; your child is predicted to break down medication at the expected rate
- Most medications should work as expected at standard doses.
- Most medications should work as expected at standard doses.
These statuses are not an indicator of your child’s health—they simply predict whether your child might need a different dose of medication or a different medication entirely. In addition to PGx test results, your child’s health-care team will still consider medical history and other factors to ensure the best treatment for your child.
To learn more about drug metabolism, metabolizing enzymes and the metabolizer status scale, see Genetics basics for pharmacogenetics.
Why is my child’s PGx status important?
CYP2C9 is an enzyme that helps break down certain medications in the body. You can think of it like a drain in a pool that controls how quickly water flows out. The water represents medication.
- If the drain is slow, water builds up.
- If the drain is too fast, water runs out quickly.
Similarly, if your child’s CYP2C9 enzyme is slower than average at breaking down certain medication, the medication might stay longer in the body, causing unwanted effects.