Drugs affected by CYP3A4
About CYP3A4
CYP3A4 metabolizes more prescription drugs than any other enzyme. Somewhere around half of everything in the formulary passes through it.[1] Most of the variation in CYP3A4 activity between people is driven by drug interactions and liver health rather than genetics, but a handful of variants (most notably CYP3A4*22) do meaningfully reduce enzyme output. Quetiapine is one of the drugs where the *22 effect is most clinically visible.[2]
Reduced-function CYP3A4 carriers reach modestly higher plasma levels of CYP3A4 substrates. The effect is usually smaller than the equivalent CYP2D6 or CYP2C19 effect, but it stacks with concurrent CYP3A4 inhibitors.
What we test for CYP3A4
Gene2Rx uses definitions covering 46 named CYP3A4 star alleles, built from 42 variants in PharmVar. Results depend on the variants available in your upload.
- Star alleles
- 46
- Defined variants
- 42
- Source
- PharmVar
- Genome build
- GRCh38
- Decreased function 8
- No function 3
- Normal function 1
- Uncertain function 34
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 CYP3A4 information
This list contains 1 medication with CYP3A4 information from the sources shown below. Evidence and report eligibility differ by drug; each page explains its scope and limitations.
Brand products containing a CYP3A4-affected ingredient
These branded medications include at least one active ingredient whose metabolism or action involves CYP3A4. Each links to its full pharmacogenetic breakdown.
References
- U.S. Food and Drug Administration. Table of Pharmacogenomic Biomarkers in Drug Labeling (2024). fda.gov
- PharmGKB / Stanford University. PharmGKB: The Pharmacogenomics Knowledge Base. pharmgkb.org
Explore CYP3A4 in your report
Informational only, not medical advice. The presence of a CYP3A4 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.