Body and biology
What Are CYP3A4 and CYP2D6? Drug Enzymes Explained
CYP3A4 and CYP2D6 · say it: sip-THREE-ay-FOR and sip-TOO-dee-SIXAlso written: CYP3A4/CYP2D6, cytochrome P450 3A4 and 2D6, CYP enzymes
Short answer
CYP3A4 and CYP2D6 are two liver enzymes that break down many medicines; labels name them to warn about drug interactions and gene differences.
What it means
CYP3A4 and CYP2D6 are two members of the cytochrome P450 family of enzymes, found mainly in the liver. Together they break down a large share of commonly used medicines. A label may say a medicine is 'metabolized by CYP3A4 and CYP2D6' when it uses both pathways.
Labels name these enzymes for two reasons. First, other medicines can slow or speed up these enzymes, changing the level of your medicine (an interaction). Second, CYP2D6 activity varies a lot between people because of their genes; some people are poor metabolizers and others are ultrarapid metabolizers. This can affect medicines such as codeine, tramadol and some antidepressants.
CYP3A4 activity is affected mostly by other medicines and foods (like grapefruit), while CYP2D6 is affected strongly by genes as well as some medicines. A pharmacogenetic test can report your CYP2D6 type.
Where you may see it
- The 'Drug interactions' and 'Clinical pharmacology' sections of medicine labels
- Pharmacogenetic test reports
- Pharmacist medication reviews
📄 How it looks on a report
This drug is primarily metabolized by CYP3A4 and CYP2D6. Inhibitors of these enzymes may increase plasma concentrations.
🙅 What it does not mean
- These are not diseases or abnormal results; they are normal enzymes everyone has.
- Being on an interaction list does not always mean you must stop a medicine; a dose change may be enough.
- A gene result for CYP2D6 does not change your health; it helps choose medicines and doses.
🗒️ Questions to ask your doctor
💊 Medicines whose labels mention “CYP3A4 and CYP2D6”
Plain-English explanations of each medicine, from its official FDA label.
- Aripiprazole
an atypical antipsychotic medicine
🔗 Read more from trusted sources
- “CYP3A4 and CYP2D6” on MedlinePlus ↗
US National Library of Medicine
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