Bexarotene and Efavirenz: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Efavirenz
No brand names on recordBexarotene
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
What happens
Reduced efavirenz exposure with reduced efficacy; reduced bexarotene exposure with reduced efficacy
Interaction Deep Dive
Concomitant use of bexarotene and efavirenz should be discouraged due to potential for virologic failure and resistance mutations, thereby reducing efavirenz efficacy. A 70-year-old HIV-1 infected male stabilized on an efavirenz-containing regimen experienced plasma viral load-confirmed virological failure 2 months after coadministration of bexarotene 300 mg/day for exacerbation of mycosis fungoides lesions. Two consecutive subtherapeutic (less than 1000 nanograms/mL) efavirenz plasma concentrations warranted efavirenz dose increase to double the dose prior to bexarotene. Simultaneously, bexarotene plasma concentrations had decreased and only partial efficacy of bexarotene on his cheek lesions was observed1. Should concomitant use be required, monitor efavirenz plasma concentrations, HIV RNA levels, and/or CD4 cell counts. In addition, dosage adjustments for either drug may be required .
Why it happens (mechanism)
Induction of either CYP3A4 metabolism or P-glycoprotein efflux of efavirenz by bexarotene; increased clearance of bexarotene by efavirenz
Literature reports
1 report — tap to read
a) A 70-year-old HIV-1 infected male experienced virological failure and partial resolution of mycosis fungoides lesions following concomitant treatment with efavirenz and bexarotene. The patient received HAART for 14 years, was drug compliant, and had undetectable plasma viral load (pVL) for the past 12 years. His medication regimen consisted of efavirenz/lamivudine/abacavir at the standard doses for the 3 years prior to bexarotene initiation. Following an acute exacerbation of past mycosis fungoides lesions on his cheek, bexarotene 300 mg/day was initiated. Two months after bexarotene initiation, 2 consecutive subtherapeutic (less than 1000 nanograms/mL) efavirenz plasma concentrations warranted efavirenz dose increase, and 2 consecutive pVL above 50 copies/mL confirmed virological failure. Simultaneously, bexarotene plasma concentrations had decreased and only partial efficacy of bexarotene on his cheek lesions was observed 1.
Common questions
Can I take Bexarotene and Efavirenz together?
Reduced efavirenz exposure with reduced efficacy; reduced bexarotene exposure with reduced efficacy Always confirm with your pharmacist or prescriber before making any change.
How serious is the Bexarotene and Efavirenz interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Bexarotene or Efavirenz need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (1)
- Desnoyer A, Kaied FA, Descamps D, et al: Deleterious pharmacokinetic interaction between bexarotene and efavirenz. AIDS 2010; 24(14):2296-2298. PubMed
Keep reading about Efavirenz
Keep reading about Bexarotene
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