Results that may predict your response to medications
The Biobank is starting to return one test result that may provide valuable insight into how you may respond to certain medications. Below is an example of what this report looks like with detailed explanations of each area of the report.
Sample Result Report from Epic
CYP2C19 and Medicines
When you take a medicine (or a drug), your body needs to find a way to use it. Some proteins in your body break down (or metabolize) medicines. Breaking down a medicine can make it more or less active, based on the medicine.
Cytochrome P450 is a family of proteins that helps your body break down certain medicines. Cytochrome P450 family 2 subfamily C member 19 (CYP2C19) (say “SIP-2-see-19”) is one certain protein in this family. It is the job of CYP2C19 to break down some medicines we use.
Pharmacogenetic Testing
DNA holds your genetic code. It lives in every one of your body’s cells. Human DNA sequences are more than 99% alike between people. Still, there are specific areas in our DNA that are known to differ between people. This means that each person has small differences in their genes.
Differences in your DNA can change how well your body breaks down certain medicines. This is called pharmacogenetics (say FAR-mah-coh-je-NEH-tiks). If you break down a medicine too fast or too slowly, this may cause the medicine to not work as well or it may cause a side effect.
By testing your DNA, we can find DNA differences that can help us to see how well your CYP2C19 protein may work in you. The results of this test can help your doctor choose a certain medicine or a certain dose of medicine that is right for you. The results of your CYP2C19 gene test will place you into one of 4 groups:
- Poor metabolizers – People in this group may have little or no active CYP2C19 protein. People who are poor metabolizers may break down some medicines more slowly. About 3% of people are CYP2C19 poor metabolizers.
- Intermediate metabolizers – People in this group may break down some medicines at a rate in between the poor and normal metabolizers. About 26% of people are CYP2C19 intermediate metabolizers.
- Normal metabolizer – People in this group are likely to have normal working CYP2C19 proteins. About 43% of people are CYP2C19 normal metabolizers.
- Ultra-rapid metabolizers – People in this group may have CYP2C19 proteins with high or very high activity. People who are rapid or ultra-rapid metabolizers may break down some medicines more quickly. About 28% of people are CYP2C19 rapid or ultra-rapid metabolizers.
Medicines that May Be Affected
CYP2C19 proteins break down many medicines that are often used. These medicines include:
- voriconazole
- used for fungal infections
- clopidogrel
- used to keep you from getting blood clots
- some tricyclic antidepressants
- used for depression
- some selective serotonin reuptake inhibitors (SSRIs)
- used for depression
- some proton pump inhibitors
- used to treat stomach ulcers and reduce stomach acid
These are the medicines that we know of right now that are broken down by CYP2C19 proteins and affected by CYP2C19 gene test results. Experts keep on finding new data about which medicines are affected by gene test results.
The result of your CYP2C19 gene test will place you into one of the 4 groups above. Knowing what group you are in may help your doctor to pick the right medicine and right dose for you.
For example, for voriconazole:
- Poor metabolizers can take longer to break down voriconazole and may have more side effects. Poor metabolizers may need a lower dose or a different medicine to treat fungal infections.
- Intermediate metabolizers most often do not need a change in the dose based on CYP2C19 gene test results.
- Normal metabolizers most often do not need a change in the dose based on CYP2C19 gene test results.
- Rapid or Ultra-rapid metabolizers may break down this medicine too quickly. They may need a different medicine to treat fungal infections.
For example, for clopidogrel in certain situations*:
- Poor metabolizers may not have enough blood clot prevention. They may need to use a different medicine to prevent blood clots.
- Intermediate metabolizers may not have enough blood clot prevention. They may need to use a different medicine to prevent blood clots.
- Normal metabolizers most often do not need a change in the dose of clopidogrel based on CYP2C19 gene test results.
- Rapid or Ultra-rapid metabolizers most often do not need a change in the dose of clopidogrel based on CYP2C19 gene test results.
*It is important to note that the clopidogrel example above does not apply to all of the reasons someone might be taking it. The facts above have only been shown to apply to patients taking this medicine after percutaneous coronary intervention (a procedure used to treat narrowing or stenosis) often with a stent placed in the artery) of the coronary arteries (of the heart) for treatment of acute coronary syndromes.
We encourage you to talk with your doctor about your CYP2C19 gene test result. Follow your doctor’s instructions when taking any medicine. Do not stop using or change any of your medicines before speaking with your doctor.
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Acknowledgements
The above information was reproduced and paraphrased with permission from St. Jude Children’s Hospital.