Cytochrome P450 3A4
CYP3A4 metabolizes more prescription drugs than any other enzyme — somewhere around half of everything in the formulary passes through it. 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.
Gene2Rx reports your CYP3A4 genotype across 46 named star alleles, built from 42 variants curated by PharmVar.
Star alleles (like *1, *2, *4) are standardized names for distinct versions of a pharmacogene. *1 is the reference; higher numbers identify variants discovered later that change the enzyme's activity.
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 tests the variants required to call every CYP3A4 allele in the PharmVar catalog.
Gene2Rx covers 1 medication with published pharmacogenetic guidance for CYP3A4, drawn from CPIC and FDA sources. Each drug links to its full pharmacogenetics page.
These branded medications include at least one active ingredient whose metabolism or action involves CYP3A4. Each links to its full pharmacogenetic breakdown.
This page lists drugs affected by CYP3A4. A Gene2Rx report tells you which metabolizer group you fall into, and what that means for every medication on this list.
Get your report Look up a medicationInformational 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.