Trospium / Xanomeline and Terbinafine: 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
Terbinafine
Trospium / 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.
Let's talk about taking terbinafine (an antifungal, like Lamisil) together with Cobenfy, which contains xanomeline and trospium. Your body uses a liver enzyme called CYP2D6 to help clear xanomeline. Terbinafine slows that enzyme down, so xanomeline may build up a bit more in your system.
If that happens, you could notice more of xanomeline's usual side effects, such as nausea, upset stomach, dizziness, or a faster heartbeat. The good news is this concern is theoretical, meaning it's based on how the drugs work rather than proven problems. Your care team can manage it easily by watching how you feel, so keep taking both as prescribed and let them know about any new side effects.
Mechanism: Terbinafine is a potent CYP2D6 inhibitor. Xanomeline (the active muscarinic agonist in Cobenfy) is significantly metabolized by CYP2D6, so inhibition may raise xanomeline exposure (AUC/Cmax).
Direction: Increased xanomeline effect and dose-related adverse reactions (cholinergic: nausea, vomiting, diarrhea, dizziness, and possible cardiovascular effects). Neither agent is a prodrug requiring activation here.
- Onset: unspecified
- Evidence: theoretical
- Severity: moderate
Management: If coadministered, monitor for increased frequency/severity of xanomeline-related adverse reactions. Dose may be individualized by the care team; consider closer monitoring during concurrent use.
What happens
Increased xanomeline exposure and an increased risk on severity and frequency of xanomeline-related adverse reactions
Interaction Deep Dive
The metabolism of xanomeline relies substantially on CYP2D6. When xanomeline is given together with inhibitors of CYP2D6, xanomeline exposure may rise, potentially raising the severity and frequency of adverse reactions associated with xanomeline. Should the two be taken at the same time, watch patients for any increase in the frequency and/or severity of xanomeline-related adverse reactions1.
Why it happens (mechanism)
Inhibition of CYP2D6-mediated metabolism of xanomeline
How to manage this interaction
Here is how a care team typically handles this combination:
- Keep taking both exactly as prescribed unless your prescriber tells you otherwise.
- Your team may monitor you more closely for xanomeline side effects while you are on terbinafine.
- The xanomeline dose may need to be adjusted and individualized by your care team if side effects increase.
Watch for and report nausea, vomiting, diarrhea, stomach cramps, dizziness, sweating, or a racing heartbeat. Since terbinafine courses are often short-term, mention to your pharmacist or doctor when you start and finish it so they can keep an eye on things.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Trospium / Xanomeline and Terbinafine together?
Terbinafine can raise xanomeline (Cobenfy) levels and make its side effects more likely, so take both as prescribed but tell your care team if you feel more nausea, dizziness, or a racing heart. This concern is theoretical and easily managed with monitoring. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Trospium / Xanomeline and Terbinafine interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Trospium / Xanomeline and Terbinafine interaction managed?
Here is how a care team typically handles this combination: Keep taking both exactly as prescribed unless your prescriber tells you otherwise. Your team may monitor you more closely for xanomeline side effects while you are on terbinafine. The xanomeline dose may need to be adjusted and individualized by your care team if side effects increase. Watch for and report nausea, vomiting, diarrhea, stom… 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 Trospium / Xanomeline or Terbinafine 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 anything you'd monitor while I'm on both?
References (1)
- Citation #1
Keep reading about Terbinafine
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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