Cimetidine 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
Cimetidine
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.
Cimetidine (Tagamet) can make your buprenorphine build up in your body. Cimetidine slows down a liver enzyme (called CYP3A4) that normally breaks buprenorphine down. When that clean-up slows, more buprenorphine stays in your blood, so its effects can be stronger and last longer.
The main thing to watch for is too much opioid effect: feeling very sleepy or foggy, or breathing that becomes slow or shallow. This is a real concern, but it is very manageable. Please don't stop or change either medicine on your own. Let your pharmacist or doctor know you take both, and they can adjust your dose and keep a closer eye on you so you stay safe and comfortable.
Mechanism: Cimetidine inhibits CYP3A4-mediated metabolism of buprenorphine, increasing buprenorphine plasma exposure. Neither drug is a prodrug here, so the net effect is increased buprenorphine effect and toxicity risk (sedation, prolonged respiratory depression).
- Direction: increased buprenorphine AUC/Cmax
- Severity/evidence: major; probable
- Onset: unspecified
Management: If a CYP3A4 inhibitor is required, consider reducing the buprenorphine dose until stable effects, monitor frequently for sedation and respiratory depression. On discontinuing cimetidine, consider a dose increase and monitor for withdrawal. For subQ (Sublocade/Brixadi) patients, monitor for over-medication; if precise titration is needed, transition to a formulation allowing finer dose adjustment.
What happens
Increased buprenorphine exposure and an increased risk of buprenorphine-related adverse events
Interaction Deep Dive
Taking buprenorphine together with a CYP3A4 inhibitor can raise buprenorphine plasma concentrations, which may lead to extended opioid effects such as respiratory depression. When a CYP3A4 inhibitor must be given to someone already taking buprenorphine, one option is to lower the buprenorphine dose until drug effects stabilize, while checking often for sedation and respiratory depression. Conversely, if a CYP3A4 inhibitor is being stopped in a patient on buprenorphine, an increase in the buprenorphine dose may be warranted until stable effects are reached, along with monitoring for opioid withdrawal signs2. Should dose adjustment prove impossible once the CYP3A4 inhibitor is no longer present, switch the patient back to a buprenorphine formulation that allows finer dose titration. For patients moved from transmucosal buprenorphine that had been given alongside CYP3A4 inhibitors, confirm through monitoring that the buprenorphine plasma level delivered by subQ buprenorphine is sufficient. When a patient already receiving subQ buprenorphine needs to start a CYP3A4 inhibitor, watch for indications of over-medication. If buprenorphine toxicity or overdose emerges yet the co-administered drug cannot be lowered or stopped, decrease the buprenorphine dose instead. When the available doses will not allow the target dose to be reached, stop treatment and manage the patient using a buprenorphine formulation that supports more precise dose adjustments 1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of buprenorphine
How to manage this interaction
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. This combination is manageable with the right adjustments and monitoring.
- Your team may reduce your buprenorphine dose and watch you closely for sedation and slow breathing while you are on cimetidine.
- If cimetidine is later stopped, they may raise your buprenorphine dose back up and watch for withdrawal, so your dose may need to be individualized.
- If you use a long-acting injectable form, they may switch you to a form that allows finer dose adjustment.
Tell your pharmacist or prescriber you take both, and get help right away for extreme drowsiness or slow, shallow breathing.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) The impact of concurrently administered CYP3A4 inhibitors on buprenorphine exposure in individuals 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 Cimetidine and Buprenorphine together?
Cimetidine can raise buprenorphine levels and increase the risk of excessive sedation and slowed breathing, so tell your care team you take both; they can adjust your dose and monitor you closely to keep you safe. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Cimetidine 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 Cimetidine and Buprenorphine interaction managed?
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. This combination is manageable with the right adjustments and monitoring. Your team may reduce your buprenorphine dose and watch you closely for sedation and slow breathing while you are on cimetidine. If cimetidine is later stopped, they may raise your buprenorphine dose back up and watch for withdrawal, s… 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 Cimetidine 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 (2)
- 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
Keep reading about Buprenorphine
Keep reading about Cimetidine
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