Propantheline 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
Propantheline
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. Propantheline also slows the gut and can make it harder to empty your bladder. When you take both together, these effects can add up.
In rare cases, the bowel can slow down so much that it nearly stops. This is called a paralytic ileus. Watch for a very bloated or painful belly, no bowel movements, or trouble passing urine. The good news is your care team can manage this by keeping an eye on you and adjusting things if needed. Keep taking both as prescribed, and call your doctor or pharmacist if these symptoms show up.
Effect: Additive risk of severe constipation, urinary retention, and potentially paralytic ileus.
Mechanism: Pharmacodynamic (additive), not metabolic. Codeine (an opioid) reduces GI motility via mu-receptor agonism; propantheline is an antimuscarinic anticholinergic that further inhibits gastric/intestinal motility and bladder emptying.
- Direction: Additive PD effect, increasing anticholinergic/opioid GI burden.
- Evidence: Theoretical; severity rated major.
- Onset: Unspecified.
- Management: Monitor for reduced gastric motility, constipation, abdominal distension, and urinary retention. Consider bowel regimen and dose individualization by the care team.
What happens
An increased risk of paralytic ileus
Interaction Deep Dive
When codeine is taken together with anticholinergic agents, there may be a heightened likelihood of urinary retention and/or severe constipation, potentially progressing to paralytic ileus. During concurrent administration of codeine and anticholinergic drugs, 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
Both medicines can slow your gut and your bladder, so using them together needs a little extra attention.
- Keep taking both as prescribed unless your doctor or pharmacist tells you otherwise.
- Your care team may monitor you more closely for constipation and trouble urinating, and the doses may need to be adjusted and individualized for you.
- Watch for a swollen or painful belly, no bowel movements, or difficulty passing urine, and report these promptly.
- Staying hydrated and asking about a stool softener or laxative plan can help.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Propantheline and Acetaminophen And Codeine together?
Taking codeine with propantheline can add up to cause severe constipation or urinary retention, and rarely a paralytic ileus. Keep taking both as prescribed, watch for a bloated painful belly or trouble urinating, and tell your doctor or pharmacist. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Propantheline 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 Propantheline and Acetaminophen And Codeine interaction managed?
Both medicines can slow your gut and your bladder, so using them together needs a little extra attention. Keep taking both as prescribed unless your doctor or pharmacist tells you otherwise. Your care team may monitor you more closely for constipation and trouble urinating, and the doses may need to be adjusted and individualized for you. Watch for a swollen or painful belly, no bowel movements, o… 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 Propantheline 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 Propantheline
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