Ritonavir and Buprenorphine: 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
Ritonavir
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.
Here's what's going on. Ritonavir (Norvir) slows down a liver enzyme called CYP3A4, which is the same enzyme your body uses to break down buprenorphine. When that enzyme is blocked, buprenorphine can build up in your body and hang around longer than usual. That can mean stronger opioid effects, like heavy drowsiness or slowed breathing.
On top of that, both medicines can affect the heart's rhythm, so together they can raise the chance of a heart-rhythm change called QT prolongation. The good news: this is very manageable. Your care team can tailor your buprenorphine dose and watch you more closely. Keep taking both as prescribed and talk with your pharmacist or doctor about it.
Mechanism: Ritonavir is a potent CYP3A4 inhibitor and reduces buprenorphine metabolism, increasing buprenorphine exposure (AUC/Cmax). Both agents also independently prolong the QT interval, giving an additive PD effect. Buprenorphine is not a prodrug, so inhibition amplifies its opioid effect.
Direction: increased buprenorphine effect (sedation, respiratory depression) plus additive QT risk. Evidence: probable. Severity: major.
- Monitor ECG/QT, sedation, and respiratory status closely.
- Consider a buprenorphine dose reduction until stable effects achieved.
- On discontinuing ritonavir, anticipate reduced buprenorphine exposure; monitor for withdrawal and consider a dose increase.
- For long-acting/subQ formulations, use products allowing precise titration if adjustment is needed.
What happens
An increased risk of QT interval prolongation, increased buprenorphine exposure and an increased risk of buprenorphine-related adverse events
Interaction Deep Dive
When buprenorphine is taken alongside a CYP3A4 inhibitor, buprenorphine plasma concentrations rise, which can lead to extended opioid effects such as respiratory depression. The concurrent use of agents that influence cardiac conduction also heightens the potential for QT prolongation. Should these drugs be given together, monitor the patient carefully for any lengthening of the QT interval. Reducing the buprenorphine dose until stable drug effects are reached should be considered, along with frequent checks for sedation and respiratory depression. Should a CYP3A4 inhibitor be stopped in a patient on buprenorphine, consider raising the buprenorphine dose until stable effects are attained, and watch for indications of opioid withdrawal2. When the dose cannot be modified after the CYP3A4 inhibitor is removed, switch the patient back to a buprenorphine formulation that allows more precise dose titration. For patients transitioned from transmucosal buprenorphine given together with CYP3A4 inhibitors, verify that the plasma buprenorphine level delivered by subQ buprenorphine is sufficient. For those already receiving subQ buprenorphine who then need a CYP3A4 inhibitor, watch for indications of over-medication. If signs and symptoms of buprenorphine toxicity or overdose appear yet the accompanying medication cannot be lowered or halted, decrease the buprenorphine dose. When the available doses do not allow the target dose to be reached, stop treatment and manage the patient using a buprenorphine formulation that permits more precise dose adjustments 1.
Why it happens (mechanism)
Additive QT interval prolongation; inhibition of CYP3A4-mediated metabolism of buprenorphine
How to manage this interaction
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This combination is used safely when the team plans for it.
Here is what your care team typically does:
- Watches you more closely for excess sedation and slowed breathing.
- May check your heart rhythm (an ECG) for QT changes.
- May adjust and individualize your buprenorphine dose while these are used together, and adjust again if ritonavir is later stopped (to avoid withdrawal).
Call your prescriber or pharmacist promptly if you notice unusual drowsiness, confusion, very slow or shallow breathing, fainting, or a racing/irregular heartbeat.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) In a study of healthy volunteers (N=12), giving oral buprenorphine together with voriconazole produced a significant rise in the mean AUC(0 to 18 hours) of buprenorphine, increasing it 4.3-fold (from 0.43 to 2.1 nanograms (ng) x hr/mL), raised the Cmax 3.9-fold (from 0.057 to 0.22 ng/mL), extended the half-life (from 9.1 to 14.5 hours), and increased urinary clearance (from 0.31 to 0.73 L/hr). Voriconazole likewise significantly raised exposure to the active metabolite norbuprenorphine, with an almost 4-fold increase in AUC(0 to 18 hours) and a 3.3-fold increase in Cmax, while decreasing its renal clearance (from 7.2 to 2.9 L/hr). Participants reported mild dizziness and nausea in both phases. Subjects were given either placebo or voriconazole 400 mg twice daily on day 1, then 200 mg twice daily on days 2 to 5, followed by a 4-week washout period before switching to the alternate regimen. On the fifth day, every subject received a single oral dose of buprenorphine, 0.2 mg or 3.6 mg during the placebo phase 3.
b) The impact of concurrently administered CYP3A4 inhibitors on buprenorphine exposure in patients receiving subQ buprenorphine has not been investigated; nevertheless, these interactions have been demonstrated in studies employing transmucosal buprenorphine. The effects of buprenorphine may vary according to the route of administration 1.
Common questions
Can I take Ritonavir and Buprenorphine together?
Ritonavir can raise buprenorphine levels and both can affect heart rhythm, so watch for over-sedation, slowed breathing, and QT changes; your care team can manage this by adjusting your buprenorphine dose and monitoring you more closely. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ritonavir and Buprenorphine 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 is the Ritonavir and Buprenorphine interaction managed?
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This combination is used safely when the team plans for it. Here is what your care team typically does: Watches you more closely for excess sedation and slowed breathing. May check your heart rhythm (an ECG) for QT changes. May adjust and individualize your buprenorphine dose while these are used together, and adj… 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 Ritonavir or Buprenorphine 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 (3)
- Product Information: BRIXADI(TM) subcutaneous extended-release injection, buprenorphine subcutaneous extended-release injection. Braeburn Inc (per FDA), Plymouth Meeting, PA, 2023. DailyMed
- Product Information: ZUBSOLV(R) sublingual tablets, buprenorphine naloxone sublingual tablets. Orexo US Inc (per FDA), Morristown, NJ, 2023. DailyMed
- Fihlman M, Hemmila T, Hagelberg NM, et al: Voriconazole greatly increases the exposure to oral buprenorphine. Eur J Clin Pharmacol 2018; 74(12):1615-1622. PubMed
Keep reading about Buprenorphine
Keep reading about Ritonavir
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Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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