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CYP2D6

Drugs affected by CYP2D6

Cytochrome P450 2D6

45 medications 48 brand products

About CYP2D6

CYP2D6 is the most clinically important pharmacogene.[1] It metabolizes around a quarter of all prescription drugs, including many antidepressants, opioids, and stimulants.[2] The gene is unusually variable: roughly 7 percent of people are poor metabolizers (they barely activate CYP2D6), and another 1 to 3 percent are ultrarapid metabolizers (their enzyme is overactive).[3]

The v4 report preserves the activity score used in its interpretation. Some medicines use a combined CYP2D6/CYP2C19 recommendation. CYP2D6 inhibitors can change functional metabolism; a genotype alone does not capture that effect.

What we test for CYP2D6

Gene2Rx uses definitions covering 148 named CYP2D6 star alleles, built from 124 variants in PharmVar. Results depend on the variants available in your upload.

148
Star alleles
124
Defined variants
PharmVar
Source
GRCh38
Genome build
Normal Function 13 Decreased Function 17 No Function 56 Uncertain Function 25 Unknown Function 37

Notable CYP2D6 alleles

*1 Normal Function
The reference allele — wild-type CYP2D6 activity; carriers are typical metabolizers.
*4 No Function
The most common no-function allele in European populations; carriers poorly metabolize codeine and many antidepressants.
~20% in Europeans
*10 Decreased Function
The dominant decreased-function allele in East Asian populations; lowers CYP2D6 activity.
~40% in East Asians
*17 Decreased Function
A decreased-function allele common in African populations.
~20% in Africans
*41 Decreased Function
A decreased-function allele caused by a splice-site variant; common in Europeans and South Asians.
What are star alleles?

Star alleles (like *1, *2, *4) are standardized names for distinct versions of a pharmacogene. *1 is the reference; other numbers identify distinct allele definitions. A higher number does not mean lower function.

You inherit one allele from each parent, so your genotype is a pair (e.g. *1/*4). The pair determines your predicted phenotype — for example, whether you metabolize a drug at a normal, decreased, or no-function rate.

PharmVar is the international registry that defines and curates these allele names. Gene2Rx uses the supported definitions summarized here. Coverage depends on the variants present in your input; this is not a guarantee that every cataloged allele can be identified.

Medications with CYP2D6 information

This list contains 45 medications with CYP2D6 information from the sources shown below. Evidence and report eligibility differ by drug; each page explains its scope and limitations.

antiarrhythmics

antidepressants - SNRI

antihistamines

drugs used in addictive disorders

estrogen modulators

gaucher's disease treatments

saliva production stimulators

urologicals

Brand products containing a CYP2D6-affected ingredient

These branded medications include at least one active ingredient whose metabolism or action involves CYP2D6. Each links to its full pharmacogenetic breakdown.

References

  1. Clinical Pharmacogenetics Implementation Consortium (CPIC). CPIC Guidelines. cpicpgx.org
  2. U.S. Food and Drug Administration. Table of Pharmacogenomic Biomarkers in Drug Labeling (2024). fda.gov
  3. PharmGKB / Stanford University. PharmGKB: The Pharmacogenomics Knowledge Base. pharmgkb.org

Explore CYP2D6 in your report

A Gene2Rx report interprets supported variants in the context of your data and purchased report. Missing or uncertain calls may prevent an assessment.

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Informational only, not medical advice. The presence of a CYP2D6 pharmacogenetic guideline does not mean every patient needs to change their dose. Never start, stop, or change a medication without talking to your prescribing clinician.

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