Amantadine and Acetaminophen And Codeine: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jun 30, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Acetaminophen And Codeine
Amantadine
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.
Your pain medicine here contains codeine (plus acetaminophen), and you're also taking amantadine. Both of these can slow down your gut and make it harder to have a bowel movement or empty your bladder. When they're used together, that slowing effect can add up. In rare cases, severe constipation can turn into a condition where the intestines nearly stop moving, called paralytic ileus.
The good news is this is a known, manageable concern. Keep taking both exactly as prescribed, and watch for hard stools, no bowel movements, bloating, belly pain, or trouble urinating. If any of those happen, call your pharmacist or doctor. Staying hydrated and active can also help keep things moving.
Effect: Additive reduction in GI and bladder motility with concurrent codeine (opioid) and amantadine (anticholinergic properties), theoretically increasing risk of severe constipation, urinary retention, and paralytic ileus.
- Mechanism: Additive effects on gastric/GI motility; opioid-induced plus anticholinergic-mediated slowing. This is a PD interaction, not a metabolic one. (Codeine is a prodrug, but that is not relevant to this motility-based interaction.)
- Direction: Increased constipation/retention risk.
- Evidence: Theoretical; severity major; onset unspecified.
- Management: Monitor for reduced gastric motility, constipation, and urinary retention. Consider bowel regimen and adequate hydration. Dose and duration may be individualized.
What happens
An increased risk of paralytic ileus
Interaction Deep Dive
Concomitant use of codeine with anticholinergic drugs may increase the risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Monitor patients for signs of urinary retention or reduced gastric motility when codeine is used concomitantly with anticholinergic drugs1.
Why it happens (mechanism)
Additive effects on gastric motility
How to manage this interaction
This interaction is manageable when you and your care team stay alert to how your gut and bladder are working.
- Keep taking both medicines as prescribed unless your doctor or pharmacist tells you otherwise.
- Your care team may monitor you more closely for constipation and urinary retention, and doses may be individualized to your needs.
- Support your gut with fluids, fiber, and movement, and ask your pharmacist whether a stool softener or laxative is right for you.
- Call promptly if you have no bowel movement for several days, severe bloating or belly pain, vomiting, or trouble passing urine.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Amantadine and Acetaminophen And Codeine together?
Combining codeine with amantadine can add up to cause serious constipation or urinary retention, so watch for these symptoms and tell your care team if they occur. This risk is theoretical but rated major, and your team can manage it with monitoring and a bowel plan. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amantadine and Acetaminophen And Codeine 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 Amantadine and Acetaminophen And Codeine interaction managed?
This interaction is manageable when you and your care team stay alert to how your gut and bladder are working. Keep taking both medicines as prescribed unless your doctor or pharmacist tells you otherwise. Your care team may monitor you more closely for constipation and urinary retention, and doses may be individualized to your needs. Support your gut with fluids, fiber, and movement, and ask your… 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 Amantadine or Acetaminophen And Codeine 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: CARISOPRODOL, ASPIRIN, CODEINE PHOSPHATE oral tablets, carisoprodol, aspirin, codeine phosphate oral tablets. Ingenus Pharmaceuticals LLC (per DailyMed), Orlando, FL, 2021. DailyMed
Keep reading about Acetaminophen And Codeine
Keep reading about Amantadine
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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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