Codeine and Amitriptyline: 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
Amitriptyline
Codeine
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.
You've been prescribed amitriptyline (an antidepressant) and codeine (a pain and cough medicine). Taken together, they can add up in two ways. First, both can affect a brain chemical called serotonin, and too much can cause serotonin syndrome, which shows up as agitation, shakiness, sweating, fast heartbeat, or confusion. Second, amitriptyline slows the gut and bladder, and codeine does too, so together they can cause severe constipation or trouble urinating, and rarely the gut can stop moving.
This is a known concern rather than something proven to happen often. The good news is your care team can manage it by watching you closely, especially when you first start or change doses. Keep taking both as prescribed, and call your doctor or pharmacist if anything feels off.
Effect: Additive risk of serotonin syndrome plus additive reduction in GI/urinary motility (severe constipation, urinary retention, possible paralytic ileus).
Mechanism: Additive serotonergic activity (both agents raise serotonergic tone) and additive anticholinergic/opioid effects on gut and bladder motility. This is a pharmacodynamic interaction, not PK-based; codeine is a CYP2D6 prodrug, but that is not the driver here.
Evidence: Theoretical; severity rated major; onset unspecified.
Management:
- Monitor for serotonin syndrome (clonus, hyperreflexia, agitation, autonomic instability), especially at initiation and dose changes.
- Monitor for urinary retention, severe constipation, and ileus.
- Discontinue codeine if serotonin syndrome is suspected.
What happens
Increased risk of paralytic ileus; increased risk of serotonin syndrome
Interaction Deep Dive
Serotonin syndrome has occurred when opioids like codeine are taken together with serotonergic agents. Combining codeine with anticholinergic medications may also heighten the likelihood of urinary retention and severe constipation, potentially progressing to paralytic ileus. Should combined therapy be required, watch the patient carefully for urinary retention, severe constipation, and any indications of serotonin syndrome2 while starting therapy and adjusting the dose. Stop codeine if serotonin syndrome is suspected 1.
Why it happens (mechanism)
Additive effects on gastric motility; additive serotonergic effects
How to manage this interaction
If your care team decides you need both, here is what they typically do and what helps:
- Keep taking both as prescribed unless your prescriber tells you otherwise.
- Expect closer monitoring, especially when starting or changing a dose. Doses may be individualized by your team.
- Watch for and report signs of serotonin syndrome: agitation, shivering, sweating, racing heart, muscle twitching, or confusion.
- Watch for severe constipation or trouble urinating, which can signal a slowed gut or bladder.
Contact your pharmacist or prescriber promptly if these appear. Serotonin symptoms can need urgent attention.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Codeine and Amitriptyline together?
Using amitriptyline with codeine can add up to raise the risk of serotonin syndrome and of severe constipation or urinary retention. Keep taking both as prescribed but watch for these signs and report them to your care team right away. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Codeine and Amitriptyline 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 Codeine and Amitriptyline interaction managed?
If your care team decides you need both, here is what they typically do and what helps: Keep taking both as prescribed unless your prescriber tells you otherwise. Expect closer monitoring, especially when starting or changing a dose. Doses may be individualized by your team. Watch for and report signs of serotonin syndrome: agitation, shivering, sweating, racing heart, muscle twitching, or confusi… 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.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Codeine or Amitriptyline 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: CARISOPRODOL, ASPIRIN, CODEINE PHOSPHATE oral tablets, carisoprodol, aspirin, codeine phosphate oral tablets. Ingenus Pharmaceuticals LLC (per DailyMed), Orlando, FL, 2021. DailyMed
- Product Information: Codeine sulfate oral tablets, codeine sulfate oral tablets. West-Ward Pharmaceuticals Corp (per DailyMed), Eatontown, NJ, 2016. DailyMed
Keep reading about Amitriptyline
Keep reading about Codeine
These medications also interact with supplements
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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