Acetaminophen And Codeine and Terodiline: 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
Terodiline
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 contains codeine, which can slow down your gut and make you constipated. Terodiline is an anticholinergic drug (it relaxes the bladder), and it can also slow the gut and make it harder to pass urine. When you take both, these effects can stack up.
In rare cases, a very sluggish gut can nearly stop moving, a serious problem called paralytic ileus. Right now this is a theoretical concern, not something proven, so try not to worry. Watch for hard constipation, belly bloating or pain, or trouble urinating, and let your care team know. They can manage this easily.
Effect: Additive reduction in GI motility and urinary retention when codeine (an opioid) is combined with terodiline (an anticholinergic), with a theoretical risk of paralytic ileus.
Mechanism: Pharmacodynamic additivity. Opioid-induced slowing of gut transit plus anticholinergic inhibition of smooth muscle and bladder tone.
- Direction: Increased constipation/urinary retention risk (additive PD effect).
- Onset: Unspecified.
- Evidence: Theoretical; severity rated major.
- Management: Monitor for reduced gastric motility, abdominal distension, and urinary retention. Consider bowel regimen; individualize dosing.
What happens
An increased risk of paralytic ileus
Interaction Deep Dive
Using codeine together with anticholinergic agents can heighten the likelihood of urinary retention and/or severe constipation, potentially progressing to paralytic ileus. When these two are administered concurrently, watch patients for indications of urinary retention or diminished gastric motility1.
Why it happens (mechanism)
Additive effects on gastric motility
How to manage this interaction
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Because both can slow the bowel and bladder, your team may keep a closer eye on you and can adjust and individualize your doses if needed.
Things you can do:
- Watch for severe constipation, belly bloating or pain, or trouble urinating, and report these promptly.
- Ask your pharmacist or doctor whether a stool softener or fiber plan makes sense for you.
- Stay hydrated and stay active as you are able.
Let your prescriber or pharmacist know you take both so they can tailor your plan.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Acetaminophen And Codeine and Terodiline together?
Codeine and terodiline can both slow your gut and bladder, so together they may raise the risk of severe constipation, urinary retention, or rarely a stalled bowel. Watch for these symptoms and tell your care team, who can adjust and monitor as needed. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Terodiline 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 Acetaminophen And Codeine and Terodiline interaction managed?
Keep taking both medicines exactly as prescribed unless your care team tells you otherwise. Because both can slow the bowel and bladder, your team may keep a closer eye on you and can adjust and individualize your doses if needed. Things you can do: Watch for severe constipation, belly bloating or pain, or trouble urinating, and report these promptly. Ask your pharmacist or doctor whether a stool… 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 Acetaminophen And Codeine or Terodiline 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
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