Doravirine 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 recordDoravirine
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
Decreased doravirine plasma concentration and reduced efficacy; increased risk of doravirine resistance
Interaction Deep Dive
Concomitant use of doravirine and efavirenz is not recommended. Coadministration may result in decreased doravirine concentration, loss of doravirine efficacy, and development of resistance. In a drug interaction study, the AUC, Cmax, and Cmin of doravirine all were decreased when given after efavirenz therapy was stopped, including up to 14 days after efavirenz discontinuation1
Why it happens (mechanism)
Induction of CYP3A-mediated doravirine metabolism
Literature reports
1 report — tap to read
a) In a drug interaction study, the AUC, Cmax, and Cmin of doravirine all were decreased when given after efavirenz therapy was stopped. The first day following the cessation of efavirenz, the doravirine AUC, Cmax, and Cmin were all decreased by 62%, 35%, and 85%, respectively. Fourteen days after the cessation of efavirenz, the AUC, Cmax, and Cmin of doravirine was still decreased by 32%, 14%, and 50%, respectively 1.
Common questions
Can I take Doravirine and Efavirenz together?
Decreased doravirine plasma concentration and reduced efficacy; increased risk of doravirine resistance Always confirm with your pharmacist or prescriber before making any change.
How serious is the Doravirine 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 "unspecified". The timing of this interaction is not well characterized.
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 Doravirine 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)
- Product Information: PIFELTRO(TM) oral tablets, doravirine oral tablets. Merck Sharp & Dohme Corp (per FDA), Whitehouse Station, NJ, 2018. DailyMed
Keep reading about Efavirenz
Keep reading about Doravirine
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