Cytochrome P450 2B6
CYP2B6 handles efavirenz (an older HIV drug), bupropion, methadone, and ketamine. The most consequential allele is *6, which dramatically reduces activity and is common across many populations. Carriers accumulate much higher efavirenz levels and are at greater risk of CNS side effects like vivid dreams and depression.
Gene2Rx reports your CYP2B6 genotype across 36 named star alleles, built from 35 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 CYP2B6 allele in the PharmVar catalog.
Gene2Rx covers 3 medications with published pharmacogenetic guidance for CYP2B6, 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 CYP2B6. Each links to its full pharmacogenetic breakdown.
This page lists drugs affected by CYP2B6. 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 CYP2B6 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.