Is Sustiva affected by genetics?

Yes — the active ingredient is metabolized by a gene known to vary between individuals.

Relevant genes: CYP2B6

Sustiva is affected by pharmacogenetics through the CYP2B6 gene. Your genotype for this gene can change how your body processes Sustiva, which can affect both how well it works and how well you tolerate it. The strongest evidence level on this page is Strong, based on CPIC or FDA guidelines.

What's in Sustiva

efavirenz affected by CYP2B6

Affected by CYP2B6 · CPIC, FDA · Strong evidence

Read the full efavirenz genetics guide →

Efavirenz phenotype recommendations

Published guidance from CPIC and FDA on how efavirenz should be dosed or substituted based on your CYP2B6 phenotype.

Phenotype	What it means	Recommendation	Evidence
Ultrarapid Metabolizer CYP2B6	Your body breaks down efavirenz slightly faster than normal, but the standard dose is still expected to be effective for you.	CPIC Initiate efavirenz with standard dosing (600 mg/day) FDA Initiate therapy with recommended starting dose.	Strong
Ultra Rapid Metabolizer CYP2B6	Your body breaks down efavirenz slightly faster than normal, but the standard dose is still expected to be effective for you.	CPIC Initiate efavirenz with standard dosing (600 mg/day) FDA Initiate therapy with recommended starting dose.	Strong
Rapid Metabolizer CYP2B6	Your body breaks down efavirenz slightly faster than normal, but the standard dose is still expected to be effective for you.	CPIC Initiate efavirenz with standard dosing (600 mg/day) FDA Initiate therapy with recommended starting dose.	Strong
Normal Metabolizer CYP2B6	Your body processes efavirenz normally. The standard dose is expected to be appropriate for you.	CPIC Initiate efavirenz with standard dosing (600 mg/day) FDA Initiate therapy with recommended starting dose.	Strong
Intermediate Metabolizer CYP2B6	Your body breaks down efavirenz more slowly than normal, which may lead to higher drug levels and an increased risk of nervous system side effects like dizziness or trouble sleeping. A lower dose may be recommended.	CPIC Consider initiating efavirenz with decreased dose of 400 mg/day. FDA Initiate therapy with recommended starting dose.	Moderate
Poor Metabolizer CYP2B6	Your body breaks down efavirenz much more slowly than normal, significantly increasing the risk of nervous system side effects like dizziness, trouble sleeping, or mood changes. A lower dose is recommended.	CPIC Consider initiating efavirenz with decreased dose of 400 or 200 mg/day. FDA Monitor closely for adverse reactions including QT prolongation due to higher systemic concentrations. Consider alternative therapy if adverse reactions occur.	Strong
Indeterminate CYP2B6	The impact of your genotype on response to this drug is unknown	CPIC + FDA Initiate therapy with recommended starting dose.	—
Not available CYP2B6	The impact of your genotype on response to this drug is unknown	CPIC + FDA Initiate therapy with recommended starting dose.	—

Sources: CPIC, FDA

Related medications

Find out how your genetics affect Sustiva

This page describes the general pharmacogenetics. A Gene2Rx report analyzes your own DNA to tell you which metabolizer group you fall into, across every medication.

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Informational only — not medical advice. Pharmacogenetic guidance describes population-level patterns; your individual response depends on many factors. Never start, stop, or change a medication without talking to your prescribing clinician.