Acetaminophen And Codeine and Solifenacin: 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
Solifenacin
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 it harder to have a bowel movement. Solifenacin (Vesicare) treats an overactive bladder, but it also tends to slow the gut and can make it harder to empty your bladder. When you take both, these effects can add up.
In rare cases, the gut can slow down so much that it nearly stops (called paralytic ileus), and you may have trouble urinating. This concern is mostly based on how the drugs work rather than a lot of real-world reports. The good news: your care team can manage this by watching for warning signs. Call them if you have severe constipation, belly pain and bloating, or trouble peeing.
Effect: Additive risk of severe constipation and urinary retention, potentially progressing to paralytic ileus.
Mechanism: Pharmacodynamic (additive) reduction in GI motility. Codeine is a mu-opioid agonist that decreases peristalsis; solifenacin is an antimuscarinic that further slows gut motility and impairs bladder emptying. This is a PD interaction, not PK; prodrug/CYP2D6 activation of codeine is not the driver here.
- Direction: increased anticholinergic/opioid GI and urinary effects
- Onset: unspecified
- Evidence: theoretical
- Severity: major
Management: Monitor for reduced bowel motility, abdominal distension, and urinary retention. Dose and duration may need individualization; consider prophylactic bowel regimen and closer clinical follow-up.
What happens
An increased risk of paralytic ileus
Interaction Deep Dive
Taking codeine together with anticholinergic agents can heighten the likelihood of urinary retention and/or serious constipation, potentially progressing to paralytic ileus. When codeine is administered alongside 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
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. Because both can slow your gut and affect bladder emptying, your care team may watch you more closely and tailor your treatment.
- Watch for warning signs: severe constipation, no bowel movements, belly swelling or pain, nausea/vomiting, or trouble urinating.
- Support your gut: ask your pharmacist whether extra fluids, fiber, or a stool softener/laxative would help while on codeine.
- Speak up: tell your pharmacist or doctor about the combination, especially if constipation lasts more than a couple of days or you cannot pass urine, so your dose or plan can be adjusted.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Acetaminophen And Codeine and Solifenacin together?
Taking codeine with solifenacin can add up to cause severe constipation and trouble urinating, and rarely a dangerously slowed gut. Keep taking both as prescribed, but call your pharmacist or doctor if you develop severe constipation, belly bloating, or trouble peeing. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Acetaminophen And Codeine and Solifenacin 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 Solifenacin interaction managed?
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. Because both can slow your gut and affect bladder emptying, your care team may watch you more closely and tailor your treatment. Watch for warning signs: severe constipation, no bowel movements, belly swelling or pain, nausea/vomiting, or trouble urinating. Support your gut: ask your pharmacist whether extra fluid… 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 Solifenacin 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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