Buprenorphine and Ensitrelvir: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Buprenorphine
Ensitrelvir
No brand names on record
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.
Buprenorphine is an opioid used for pain or for treating opioid dependence. Ensitrelvir is an antiviral. Ensitrelvir slows down a liver enzyme (called CYP3A) that normally breaks buprenorphine down. When that enzyme is blocked, buprenorphine can build up in your body to higher levels than expected.
That extra buildup can raise the chance of opioid side effects like heavy drowsiness, confusion, or slowed breathing. Because of this, taking these two together is not recommended. The good news is your care team can plan around this by carefully timing the medicines and watching you closely. Please talk with your pharmacist or doctor before combining them.
Mechanism: Ensitrelvir is a potent CYP3A inhibitor. Buprenorphine is metabolized substantially by CYP3A4 (to norbuprenorphine), so co-administration is expected to increase buprenorphine exposure (increased AUC/Cmax) and the risk of opioid-related adverse effects (sedation, respiratory depression).
- Direction: increased buprenorphine effect (enzyme inhibition; buprenorphine is an active drug, not a prodrug requiring CYP3A activation).
- Magnitude: not specific to buprenorphine; probe substrates showed midazolam AUC up ~6.8-fold, dexamethasone AUC up ~3.5-fold.
- Evidence: probable. Severity: contraindicated per labeling.
- Management: Inhibition persists after the last dose; note residual effect at 5 and 10 days on probe substrates. Reintroduce/adjust based on assessment of inhibition duration and patient factors, with enhanced monitoring.
What happens
Increased CYP3A substrates exposure and an increased risk of CYP3A substrates-related adverse effects
Interaction Deep Dive
Giving ensitrelvir together with CYP3A substrates is contraindicated, since doing so can raise the exposure of those substrates and lead to adverse effects. In interaction studies, when midazolam (a CYP3A substrate) was given as a single 2 mg oral dose alongside ensitrelvir at its clinical dose (375 mg on day 1 followed by 125 mg on days 2 through 5) on Day 5, the midazolam Cmax rose roughly 2.80-fold and its AUC(0 to inf) increased 6.77-fold relative to midazolam given by itself. Similarly, coadministration of a single 1 mg dose of dexAMETHasone with ensitrelvir (750 mg on day 1 and 250 mg on days 2 through 5, which is twice the recommended dose) on day 5, and dexAMETHasone given alone on day 9 (5 days after the final ensitrelvir dose) and day 14 (10 days after the final ensitrelvir dose), produced an approximately 1.47-fold rise in Cmax and a 3.47-fold rise in AUC(0 to inf) of dexAMETHasone on day 5, a 1.24-fold rise in Cmax and 2.38-fold rise in AUC(0 to inf) on day 9, and a 1.17-fold rise in Cmax and a 1.58-fold rise in AUC(0 to inf) on day 14, all compared with dexAMETHasone taken alone. Ensitrelvir should be started only after carefully weighing the relevant clinical and pharmacokinetic factors tied to the concomitant medication. Furthermore, restarting contraindicated CYP3A substrates should be considered on the basis of an evaluation of how long CYP3A inhibition persists together with patient specific considerations1.
Why it happens (mechanism)
Inhibition of CYP3A-mediated metabolism by ensitrelvir
How to manage this interaction
This combination is labeled as contraindicated, so your care team will look closely at both medicines before using them together.
- Do not stop or change either medicine on your own. Talk with your prescriber or pharmacist first.
- Your team may choose to start ensitrelvir only after evaluating your buprenorphine therapy, or adjust timing.
- Because the enzyme-blocking effect can linger for days after the last ensitrelvir dose, your team decides when it is safe to resume or restart medicines, individualized to you.
- Report increased drowsiness, confusion, or slowed or difficult breathing right away.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) When midazolam (a CYP3A substrate) was given as a single 2 mg oral dose together with ensitrelvir at the clinical dose (375 mg on day 1 and 125 mg on days 2 to 5) on Day 5, the Cmax of midazolam rose by roughly 2.80-fold and its AUC(0 to inf) rose by 6.77-fold relative to midazolam given by itself. In addition, giving dexAMETHasone (single 1 mg dose) along with ensitrelvir (750 mg on day 1 and 250 mg on days 2 to 5, twice the recommended dose) on day 5, and dexAMETHasone alone on day 9 (5 days after the final ensitrelvir dose) and day 14 (10 days after the final ensitrelvir dose), produced an approximately 1.47-fold increase in Cmax and a 3.47-fold increase in AUC(0 to inf) of dexAMETHasone on day 5, a 1.24-fold increase in Cmax and 2.38-fold increase in AUC(0 to inf) on day 9, and a 1.17-fold increase in Cmax and a 1.58-fold increase in AUC(0 to inf) on day 14, compared with dexAMETHasone given alone 1.
Common questions
Can I take Buprenorphine and Ensitrelvir together?
Ensitrelvir can raise buprenorphine levels and increase opioid side effects, so the combination is treated as contraindicated. Do not combine them without your prescriber or pharmacist guiding the timing and monitoring. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Buprenorphine and Ensitrelvir interaction?
It is rated contraindicated. These should generally not be used together.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Buprenorphine and Ensitrelvir interaction managed?
This combination is labeled as contraindicated, so your care team will look closely at both medicines before using them together. Do not stop or change either medicine on your own. Talk with your prescriber or pharmacist first. Your team may choose to start ensitrelvir only after evaluating your buprenorphine therapy, or adjust timing. Because the enzyme-blocking effect can linger for days after t… Management is individual — always follow your own care team's guidance.
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 Buprenorphine or Ensitrelvir 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: XOCOVA® oral tablets, ensitrelvir oral tablets. Shionogi Inc. Florham Park, NJ, 2026.
Keep reading about Buprenorphine
Keep reading about Ensitrelvir
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