Oxymorphone and Trospium / Xanomeline: 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
Oxymorphone
No brand names on recordTrospium / Xanomeline
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.
These two medicines can team up in a way that slows down your gut and bladder. Oxymorphone is a strong opioid pain medicine, and opioids naturally cause constipation and can make it harder to empty your bladder. The Cobenfy combination contains trospium, which has anticholinergic effects that also slow the gut and bladder. Together, the concern is more constipation and trouble urinating, and in rare cases the bowel can nearly stop moving.
The good news: this is a theoretical concern, and your care team can manage it. Watch for a swollen, painful belly, no bowel movements, or trouble peeing, and let your pharmacist or doctor know. Staying hydrated and active also helps.
Interaction: Additive pharmacodynamic effect. Oxymorphone (mu-opioid agonist) reduces GI motility and bladder emptying; trospium (a quaternary anticholinergic component of Cobenfy) adds antimuscarinic slowing of gut and bladder tone.
- Direction: Increased risk of urinary retention and severe constipation, potentially paralytic ileus.
- Mechanism: Unknown/additive PD; no clear PK basis. Neither agent is dependent on the other for activation.
- Evidence: Theoretical. Onset unspecified.
- Management: Monitor for reduced gastric motility (abdominal distension, absent bowel sounds, no stool) and urinary retention. Consider prophylactic bowel regimen; individualize opioid dosing.
What happens
Increased risk of urinary retention and/or severe constipation leading to paralytic ileus
Interaction Deep Dive
Taking oxyMORphone together with anticholinergic agents can heighten the likelihood of urinary retention and/or severe constipation, potentially progressing to paralytic ileus. When oxyMORphone is combined with anticholinergic medications, watch patients for indications of urinary retention or diminished gastric motility1.
Why it happens (mechanism)
Unknown
How to manage this interaction
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. The main job here is watching for and preventing bowel and bladder slowdown.
- Watch for constipation (no bowel movement, bloating, belly pain) and trouble urinating (can't fully empty, weak stream, pain).
- Ask your care team about a bowel routine such as fluids, fiber, and a stool softener or laxative if appropriate.
- Your team may monitor you more closely, and your opioid dose may need to be adjusted and individualized.
- Call promptly for a swollen, painful belly with vomiting or an inability to pass gas, stool, or urine.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Oxymorphone and Trospium / Xanomeline together?
Using oxymorphone with trospium (in Cobenfy) can add up to worse constipation and urinary retention, so watch for these symptoms and ask your care team about a bowel and monitoring plan. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Oxymorphone and Trospium / Xanomeline 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 Oxymorphone and Trospium / Xanomeline interaction managed?
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. The main job here is watching for and preventing bowel and bladder slowdown. Watch for constipation (no bowel movement, bloating, belly pain) and trouble urinating (can't fully empty, weak stream, pain). Ask your care team about a bowel routine such as fluids, fiber, and a stool softener or laxative if appropriate… 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 Oxymorphone or Trospium / Xanomeline 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: OPANA(R) ER oral extended-release tablets, oxymorphone HCl oral extended-release tablets. Endo Pharmaceuticals Inc (per FDA), Malvern, PA, 2023. DailyMed
Keep reading about Oxymorphone
Keep reading about Trospium / Xanomeline
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