Amitriptyline and Dihydrocodeine: 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
Dihydrocodeine
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.
Amitriptyline (Elavil) and dihydrocodeine can add up in two ways when taken together. First, both can raise a brain chemical called serotonin, and too much can cause a reaction called serotonin syndrome. Watch for agitation, a fast heartbeat, sweating, shivering, twitchy muscles, or confusion. Second, amitriptyline can dry things out and slow your gut and bladder, and dihydrocodeine does the same. Together they can cause bad constipation or trouble peeing.
The good news is your care team can manage this. They may watch you a bit more closely, especially when starting or changing doses. Keep taking both as prescribed and call your pharmacist or doctor with any of these symptoms.
Effect: Additive risk of serotonin syndrome and additive anticholinergic/opioid effects raising risk of urinary retention, severe constipation, and paralytic ileus.
- Mechanism: Additive serotonergic activity (amitriptyline TCA plus dihydrocodeine opioid); additive antimuscarinic and reduced GI motility effects. PD interaction, not primarily PK.
- Severity/evidence: Major; theoretical.
- Onset: Unspecified; higher risk at initiation and dose changes.
- Management: If co-use is needed, monitor for serotonin syndrome (autonomic instability, neuromuscular changes, mental status change) and for reduced gastric motility/urinary retention. Discontinue dihydrocodeine if serotonin syndrome is suspected. Dosing individualized by the care team.
What happens
Increased risk of paralytic ileus and an increased risk of serotonin syndrome
Interaction Deep Dive
Taking opioids like dihydrocodeine together with serotonergic agents can lead to serotonin syndrome. Combining dihydrocodeine with anticholinergic medications may also heighten the likelihood of urinary retention and severe constipation, potentially progressing to paralytic ileus. When such combined use cannot be avoided, monitor the patient closely, especially when starting therapy and when adjusting doses, watching for serotonin syndrome as well as for indications of urinary retention or diminished gastric motility. If serotonin syndrome is suspected, stop dihydrocodeine1.
Why it happens (mechanism)
Unknown; additive serotonergic effects
How to manage this interaction
Your care team can manage these two together by watching you more closely, especially when either medicine is started or its dose is changed.
- Keep taking both as prescribed unless your prescriber tells you otherwise.
- Report signs of serotonin syndrome: agitation, confusion, racing heart, sweating, shivering, tremor, or muscle stiffness.
- Report gut and bladder problems: severe constipation, bloating, belly pain, or trouble urinating.
- Ask about stool softeners or fluids if constipation becomes a problem.
If serotonin syndrome is suspected, the dihydrocodeine may be stopped, so seek care promptly. Bring your full medication list to your pharmacist or doctor so doses can be tailored to you.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) Instances of serotonin syndrome, a condition that can be life-threatening, have been documented when opioids are taken together with serotonergic agents 1.
Common questions
Can I take Amitriptyline and Dihydrocodeine together?
Taking amitriptyline with dihydrocodeine can add up to cause serotonin syndrome or severe constipation and urinary retention, so watch for these symptoms and stay in touch with your care team, especially when starting or changing doses. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amitriptyline and Dihydrocodeine 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 Amitriptyline and Dihydrocodeine interaction managed?
Your care team can manage these two together by watching you more closely, especially when either medicine is started or its dose is changed. Keep taking both as prescribed unless your prescriber tells you otherwise. Report signs of serotonin syndrome: agitation, confusion, racing heart, sweating, shivering, tremor, or muscle stiffness. Report gut and bladder problems: severe constipation, bloatin… 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 Amitriptyline or Dihydrocodeine 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: SYNALGOS(R)-DC oral capsules, aspirin, caffeine, dihydrocodeine bitartrate oral capsules. Sun Pharmaceuticals Industries Inc (per FDA), Cranbury, NJ, 2023. DailyMed
Keep reading about Amitriptyline
Keep reading about Dihydrocodeine
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