Amantadine 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
Amantadine
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.
Amantadine and trospium (found in Cobenfy) both have mild drying, or "anticholinergic," effects. When you take them together, those effects can add up. That can mean things like dry mouth, blurry vision, constipation, trouble urinating, and in some cases confusion or even seeing things that aren't there.
The good news is that this is a theoretical concern, meaning it's based on how these drugs work rather than lots of real-world reports with this exact pair. Please don't stop either medicine on your own. Just let your pharmacist or doctor know so they can watch for these side effects and adjust a dose if needed.
Mechanism: additive (pharmacodynamic) anticholinergic activity. Amantadine has intrinsic anticholinergic-like properties; trospium is a peripheral antimuscarinic. Combined use may potentiate atropine-like effects. Neither is a prodrug requiring activation, so the interaction is straightforwardly additive PD, not PK.
- Direction: increased anticholinergic burden (peripheral: dry mouth, blurred vision, urinary retention, constipation; central: confusion, hallucinations).
- Evidence: theoretical; documented CNS effects historically seen with amantadine plus high-dose antimuscarinics (trihexyphenidyl, benztropine).
- Onset: unspecified.
- Management: monitor for atropine-like effects; if they occur, reduce dose of the anticholinergic or amantadine. Individualize.
What happens
Potentiation of anticholinergic effects
Interaction Deep Dive
Using amantadine at the same time as anticholinergic agents can heighten the anticholinergic-type adverse effects associated with amantadine21. When the two have been given together, an intensification of anticholinergic side effects has occurred, such as confusion and hallucinations, in patients taking doses near the maximum tolerated level of an anticholinergic (trihexyphenidyl, benztropine)3. Should concurrent administration be necessary, lower the dose of either the anticholinergic agent or amantadine if atropine-like side effects develop2.
Why it happens (mechanism)
Additive anticholinergic properties
How to manage this interaction
Keep taking both medications as prescribed unless your care team tells you otherwise. This is a manageable interaction.
- Watch for dry mouth, blurred vision, constipation, difficulty urinating, and any new confusion or hallucinations.
- If these occur, your team may lower the dose of either the anticholinergic (trospium) or amantadine. The right dose can be adjusted and individualized by your care team.
- Tell your pharmacist or prescriber about any bothersome symptoms, especially confusion, so they can monitor you more closely.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) The combined use of amantadine and anticholinergic medications has been documented to enhance anticholinergic adverse effects, such as confusion and hallucinations, in patients who were taking doses of an anticholinergic (trihexyphenidyl, benztropine) approaching the maximum tolerable level 3.
Common questions
Can I take Amantadine and Trospium / Xanomeline together?
Taking amantadine with trospium can add up their drying side effects (dry mouth, blurred vision, constipation, trouble urinating, and possibly confusion). Keep taking both as prescribed and report any of these symptoms so your team can adjust a dose. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amantadine 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 Amantadine and Trospium / Xanomeline interaction managed?
Keep taking both medications as prescribed unless your care team tells you otherwise. This is a manageable interaction. Watch for dry mouth, blurred vision, constipation, difficulty urinating, and any new confusion or hallucinations. If these occur, your team may lower the dose of either the anticholinergic (trospium) or amantadine. The right dose can be adjusted and individualized by your care te… 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 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 (3)
- Citation #5
- Product Information: OSMOLEX ER(TM) oral extended-release tablets, amantadine oral extended-release tablets. Vertical Pharmaceuticals, LLC (per manufacturer), Bridgewater, NJ, 2018. DailyMed
- Postma JU & Tilburg WV: Visual hallucinations and delirium during treatment with amantadine (Symmetrel(R)). J Am Geriatr Soc 1975; 23:212-215. PubMed
Keep reading about Amantadine
Keep reading about Trospium / Xanomeline
These medications also interact with supplements
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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