Buprenorphine and Doxepin: 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
Doxepin
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 (a pain or addiction medicine) and doxepin (used for depression, sleep, or itching) can add up in a few ways when taken together. Both can slow down your brain and breathing, which may leave you very sleepy or foggy. Both can affect your heart's rhythm (something called the QT interval), and both can slow your gut, which can lead to serious constipation. There is also a small chance of serotonin syndrome, which can cause agitation, shakiness, sweating, or a fast heartbeat.
The good news: your care team knows how to manage this. They may adjust your doses and watch you a little more closely. Keep taking both as prescribed and call your pharmacist or doctor with any questions.
Interaction: Additive risk of QT prolongation, serotonin syndrome, paralytic ileus, and CNS/respiratory depression with concurrent buprenorphine and doxepin.
Mechanism: Pharmacodynamic (additive), not PK. Both agents prolong QT, exert serotonergic activity, reduce GI motility, and depress the CNS. Neither is a relevant prodrug in this context.
- Direction: Additive potentiation of shared effects.
- Evidence: Theoretical; severity rated major.
- Onset: Unspecified.
- Management: Avoid if possible. If combined, monitor at initiation and dose changes for sedation, QT (ECG/electrolytes), serotonin toxicity, and constipation/ileus. Consider dose reduction of doxepin and/or buprenorphine per tolerability; discontinue if serotonin syndrome suspected.
What happens
An increased risk of QT interval prolongation, an increased risk of serotonin syndrome, an increased risk of paralytic ileus and an increased risk of CNS depression
Interaction Deep Dive
The combined use of buprenorphine with medications capable of prolonging the QT interval, doxepin among them, should be avoided 34. Because doxepin also acts on the serotonergic neurotransmitter system, taking it alongside buprenorphine can heighten the likelihood of serotonin syndrome. When such combined use cannot be avoided, the patient should be monitored, particularly at the start of therapy and when doses are changed, and the regimen should be stopped if serotonin syndrome is suspected. Watch for indications of severe constipation, since this may progress to paralytic ileus 21. Taking doxepin together with CNS depressants like buprenorphine can produce CNS effects that potentiate the sedative action of the CNS depressants. A reduction in the dose of doxepin and/or the CNS depressant may be warranted depending on clinical response and tolerability 5.
Why it happens (mechanism)
Additive QT interval prolongation; additive serotonergic effects; additive effects on gastric motility; additive CNS depression
How to manage this interaction
Your care team can manage this combination safely. Here is what they typically do and what you can do:
- Keep taking both as prescribed unless your prescriber tells you otherwise.
- Your team may adjust and individualize your doses and monitor you more closely, especially when you first start or change a dose.
- They may check your heart rhythm (ECG) since both drugs can affect the QT interval.
- Watch for severe constipation, extreme drowsiness or slowed breathing, and signs of serotonin syndrome (agitation, tremor, sweating, fast heartbeat, confusion).
Get medical help right away if those symptoms appear, and ask your pharmacist or prescriber before adding any new medicine.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Buprenorphine and Doxepin together?
Taking buprenorphine and doxepin together can add up to cause heart rhythm changes, heavy sedation, serious constipation, and a small risk of serotonin syndrome, so your care team may adjust doses and monitor you closely. Keep taking both as prescribed and report severe drowsiness, constipation, or agitation right away. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Buprenorphine and Doxepin 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 Buprenorphine and Doxepin interaction managed?
Your care team can manage this combination safely. Here is what they typically do and what you can do: Keep taking both as prescribed unless your prescriber tells you otherwise. Your team may adjust and individualize your doses and monitor you more closely, especially when you first start or change a dose. They may check your heart rhythm (ECG) since both drugs can affect the QT interval. Watch fo… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Buprenorphine or Doxepin 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 (5)
- Product Information: BRIXADI(TM) subcutaneous extended-release injection, buprenorphine subcutaneous extended-release injection. Braeburn Inc (per FDA), Plymouth Meeting, PA, 2023. DailyMed
- Product Information: BUTRANS(R) transdermal system patch, buprenorphine transdermal system patch. Purdue Pharma L.P. (per FDA), Stamford, CT, 2016. DailyMed
- Product Information: BELBUCA(TM) buccal film, buprenorphine buccal film. Endo Pharmaceuticals Inc. (per FDA), Malvern, PA, 2016.
- Product Information: BUPRENEX(R) intravenous injection, intramuscular injection, buprenorphine HCl intravenous injection, intramuscular injection. Indivior Inc. (per DailyMed), Richmond, VA, 2016. DailyMed
- Product Information: SINEQUAN(R) oral capsules, oral solution, doxepin HCl oral capsules, oral solution. Pfizer Inc. (per FDA), New York, NY, 2025.
Keep reading about Buprenorphine
Keep reading about Doxepin
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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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