Sirolimus 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
Sirolimus
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.
Here's what's going on. Sirolimus (Rapamune) is what we call a "narrow window" medicine, meaning the right amount in your body matters a lot. Cobenfy contains xanomeline, which can briefly slow down the way your gut breaks down and pushes out sirolimus. The result is that a little more sirolimus may get absorbed than usual.
That could mean stronger effects and more side effects from your sirolimus, like mouth sores, swelling, or changes in your blood counts. The good news is this is a theoretical concern, and it's very manageable. Your care team can check your sirolimus blood levels and adjust the dose if needed. Please don't change anything on your own, just let your pharmacist or doctor know you take both.
Mechanism: Xanomeline (in Cobenfy) transiently inhibits intestinal CYP3A4 and P-gp locally in the gut (not systemically). Sirolimus is a sensitive CYP3A4 substrate, a P-gp substrate, and a narrow-therapeutic-index agent, so gut-level inhibition may increase its oral bioavailability and exposure (AUC/Cmax).
Direction: Increased sirolimus exposure, raising risk/severity of dose-related adverse effects (mucositis, cytopenias, dyslipidemia, edema, nephrotoxicity).
- Evidence: Theoretical.
- Onset: Unspecified.
- Management: Monitor for increased adverse reactions; use sirolimus therapeutic drug monitoring (trough whole-blood levels). Dose individualized by the care team.
What happens
Increased oral sensitive CYP3A4 substrate that are P-gp substrates with NTI exposure and an increased risk on severity and frequency of sensitive CYP3A4 substrate that are P-gp substrates with NTI-related adverse reactions
Interaction Deep Dive
Within the gut, xanomeline produces a transient, local inhibition of both CYP3A4 and P-gp, without exerting this effect systemically. When xanomeline is taken alongside oral medications that are sensitive CYP3A4 substrates, the exposure to those oral drugs (specifically the sensitive CYP3A4 substrates that are also P-gp substrates with an NTI) may rise. Such an increase can result in adverse reactions from these substrates occurring more frequently and/or with greater severity. Should the two be given together, watch patients for a higher frequency and/or greater severity of adverse reactions tied to oral drugs that are sensitive CYP3A4 substrates and also P-gp substrates with NTI1.
Why it happens (mechanism)
Inhibition of CYP3A4-substrate metabolism by xanomeline; inhibition of P-gp-mediated efflux transport by xanomeline
How to manage this interaction
The key here is monitoring. Because sirolimus has a narrow safe range, your care team already checks its blood levels, and they can use those checks to keep you in the right zone if you also take Cobenfy.
- Keep taking both medicines exactly as prescribed unless your prescriber tells you otherwise.
- Your sirolimus dose may need to be adjusted and individualized by your care team, and they may monitor you more closely (including blood levels).
- Watch for and report increased side effects like mouth sores, swelling, unusual tiredness, or infections.
- Tell your pharmacist and prescriber that you take both so they can plan the timing of your lab checks.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Sirolimus and Trospium / Xanomeline together?
Cobenfy (xanomeline) may raise your sirolimus levels by briefly slowing its breakdown in the gut, so your care team may monitor sirolimus blood levels more closely and adjust the dose. Keep taking both as prescribed and report any new or worsening side effects. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Sirolimus and Trospium / Xanomeline 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 Sirolimus and Trospium / Xanomeline interaction managed?
The key here is monitoring. Because sirolimus has a narrow safe range, your care team already checks its blood levels, and they can use those checks to keep you in the right zone if you also take Cobenfy. Keep taking both medicines exactly as prescribed unless your prescriber tells you otherwise. Your sirolimus dose may need to be adjusted and individualized by your care team, and they may monitor… 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 Sirolimus 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 anything you'd monitor while I'm on both?
References (1)
- Citation #1
Keep reading about Sirolimus
Keep reading about Trospium / Xanomeline
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