Cytochrome P450 2D6 (CYP2D6) and Medicines

What is CYP2D6?

When you take a medicine, your body needs a way to handle it. One way your body does this is by using enzymes to break down (metabolize) the medicine. A family of enzymes called cytochrome P450 breaks down certain medicines. Enzymes make a medicine more or less active, depending on the type of medicine.

Cytochrome P450 2D6 (known as CYP2D6) enzymes break down several medicines people often use. These include:

• Codeine
• Tramadol
• Some other pain relievers 
• Atomoxetine
• Ondansetron
• Tamoxifen
• Some medicines to treat depression (such as amitriptyline, fluvoxamine, imipramine, venlafaxine, and vortioxetine)
• Some medicines to treat mental health disorders (such as atomoxetine)
• Metoprolol (a medicine used for heart conditions and high blood pressure)

How pharmacogenomic testing works

Each person differs from another at the DNA level. Genes are parts of DNA that act like instructions and tell the body how to work. The CYP2D6 gene is a section of DNA that instructs how well CYP2D6 enzymes work.

The study of how genes like CYP2D6 affect the way your body interacts with medicines is called pharmacogenomics. Differences in your DNA that make up the CYP2D6 gene can affect how well you are able to break down certain medicines.

If you break down a medicine too fast or too slow, the medicine may not work as well, or you may have more side effects.

A pharmacogenomic test looks for differences that can help your medical team know how well your CYP2D6 enzyme will work. The test results can help your doctors and pharmacists choose the correct type or dose of medicine to give you. 

Please share your pharmacogenomic test results with all your new doctors and pharmacists. 

After pharmacogenomic testing

The results of your CYP2D6 test will place you into 1 of 5 CYP2D6 gene groups:

• Ultra-rapid metabolizer: People in this group have a very high activity of CYP2D6 enzymes. They break down some medicines faster than normal and are likely to need a different dose or type of medicine. About 3% (3 in 100) of people are in this group.
• Normal metabolizer: People in this group have normal working CYP2D6 enzymes. About 57% (57 in 100) of people are in this group.
• Intermediate metabolizer: People in this group have lower than normal CYP2D6 enzyme function. They break down some medicines more slowly. About 29% (29 in 100) of people are in this group.
• Poor metabolizer: People in this group have little or no active CYP2D6 enzymes. People who are poor metabolizers break down some medicines slowly and are likely to need a different dose or different type of medicine. About 5% (5 in 100) of people are this group.
• Indeterminate phenotype: A small number of people will have unknown function of their CYP2D6 enzyme based on their test. About 6% (6 in 100) of people are in this group.

Scientists continue to find new information about which medicines are affected by genes. Talk to your doctor or pharmacist if you have questions about your medicines, side effects, or pharmacogenomic testing.

Find more information about genes that are being used to make medication therapy decisions for patients at patients at St. Jude.

If you have questions about pharmacogenomic testing done at St. Jude, you can email the Clinical Pharmacogenomics Program at pharmacogenomics@stjude.org.

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