U.S. flag

An official website of the United States government

GTR Home > Conditions/Phenotypes > Efavirenz response


Efavirenz is a non-nucleoside reverse transcriptase inhibitor widely used worldwide to treat HIV-1 infection. It is predominantly metabolized into inactive metabolites by cytochrome P450-2B6 (CYP2B6). Genetic variants in CYP2B6 (e.g. CYP2B6*6 and *18), along with other genetic and non-genetic factors, are known to influence variability in efavirenz response. Patients with certain CYP2B6 genetic polymorphisms may be at increased risk for adverse effects, particularly central nervous system toxicity and treatment discontinuation. [from PharmGKB]

Genes See tests for all associated and related genes

  • Also known as: CPB6, CYP2B, CYP2B7, CYP2B7P, CYPIIB6, EFVM, IIB1, P450, CYP2B6
    Summary: cytochrome P450 family 2 subfamily B member 6

Practice guidelines

  • PAGAA, 2020
    Panel on Antiretroviral Guidelines for Adults and Adolescents. Guidelines for the Use of Antiretroviral Agents in Adults and Adolescents with HIV. Department of Health and Human Services.
  • DailyMed Drug Label, 2020
    DailyMed Drug Label, SUSTIVA- efavirenz, 2020

Consumer resources

IMPORTANT NOTE: NIH does not independently verify information submitted to the GTR; it relies on submitters to provide information that is accurate and not misleading. NIH makes no endorsements of tests or laboratories listed in the GTR. GTR is not a substitute for medical advice. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.