Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.
Efavirenz is an HIV medicine of the NNRTI group (non-nucleoside reverse transcriptase inhibitors): it blocks reverse transcriptase, the enzyme HIV needs to copy itself into a cell's DNA. It is taken together with other HIV medicines. It is sold as Sustiva, among other names, and is part of several combination tablets.
Efavirenz is broken down mainly by the liver enzyme CYP2B6. The common variant CYP2B6*6 (which carries rs3745274) makes the enzyme work more slowly; people with two slow copies, up to about 1 in 5 in some African populations, have much higher blood levels, with more side effects such as dizziness, vivid dreams and trouble sleeping. CPIC and DPWG have published guidelines on CYP2B6 and efavirenz. Studies have also looked at CYP2A6, the transporter ABCB1 and other genes, with weaker evidence.
Clinical guidelines that name a gene for Efavirenz. They sort people into groups by the gene copies they carry.
US FDA: CYP2B6. Poor Metabolizer. Data that Indicate a Potential Impact on Safety or Response.
Every published finding on gene variants and Efavirenz. Upload your DNA file to see which of these rows apply to you.
PharmGKB weighs all studies of a variant and rates how strong the evidence is, from 1A (strongest) to 4.
CYP2B6 rs3745274: Level 1A · replicated. Metabolism/PK: HIV infectious disease. 78.
CYP2B6 CYP2B6*1, CYP2B6*4, CYP2B6*6, CYP2B6*9, CYP2B6*18, CYP2B6*28: Level 1A · replicated. Metabolism/PK: HIV infectious disease. 44.
CYP2B6 rs3745274: Level 1A · replicated. Toxicity: HIV infectious disease. 29.
CYP2B6 CYP2B6*1, CYP2B6*2, CYP2B6*6, CYP2B6*18, CYP2B6*38: Level 1A · replicated. Toxicity: HIV infectious disease. 12.
Studies of how quickly the body processes this medication.
Studies of how well it worked in people carrying a variant.
Studies of how much of the drug people needed or tolerated.
Study findings and evidence levels: PharmGKB (CC BY-SA 4.0). Guidelines: CPIC and DPWG, as bundled in PharmCAT. Most studies were done mainly in people of European ancestry.
More drugs from the same category
Not a prescribing recommendation. This page is educational information about pharmacogenomic research and clinical guidelines - it is not medical or dosing advice, and not a prediction of how any medication will work for you. Never start, stop, or change a medication or dose based on it; talk to your doctor or pharmacist, who can order clinical-grade testing if appropriate.
Content updated September 2026.
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