Drugs affected by CYP2B6
About CYP2B6
CYP2B6 handles efavirenz (an older HIV drug), bupropion, methadone, and ketamine.[1] 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.[2]
CPIC recommends a lower starting efavirenz dose for poor and intermediate CYP2B6 metabolizers. The dose-response relationship is strong enough that some clinicians measure drug levels directly.[3]
What we test for CYP2B6
Gene2Rx uses definitions covering 36 named CYP2B6 star alleles, built from 35 variants in PharmVar. Results depend on the variants available in your upload.
- Star alleles
- 36
- Defined variants
- 35
- Source
- PharmVar
- Genome build
- GRCh38
- Normal Function 6
- Increased Function 2
- Decreased Function 9
- No Function 9
- Uncertain Function 8
- Unknown Function 2
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 CYP2B6 information
This list contains 3 medications with CYP2B6 information from the sources shown below. Evidence and report eligibility differ by drug; each page explains its scope and limitations.
antiretrovirals
Brand products containing a CYP2B6-affected ingredient
These branded medications include at least one active ingredient whose metabolism or action involves CYP2B6. Each links to its full pharmacogenetic breakdown.
References
- U.S. Food and Drug Administration. Table of Pharmacogenomic Biomarkers in Drug Labeling (2024). fda.gov
- Clinical Pharmacogenetics Implementation Consortium (CPIC). CPIC Guidelines. cpicpgx.org
- PharmGKB / Stanford University. PharmGKB: The Pharmacogenomics Knowledge Base. pharmgkb.org
Explore CYP2B6 in your report
Informational 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.