Drug interactions
Clozapine + Fesoterodine
Severity: Major
Clozapine and Fesoterodine: major interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Clozapine is strongly anticholinergic, and adding fesoterodine increases the risk of constipation, which with clozapine can progress to serious gastrointestinal hypomotility or ileus. Urinary retention, tachycardia and delirium may also occur.
What this interaction means in plain words
Clozapine and Fesoterodine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Clozapine belongs to Central Nervous System; Fesoterodine belongs to Genitourinary.
Why it happens
Additive antimuscarinic effects causing reduced gastrointestinal and bladder motility.
What to do
Avoid the combination if possible; if used, monitor bowel function closely, treat constipation proactively, and review for alternatives such as a non-antimuscarinic bladder agent.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Fesoterodine
Other interactions of Clozapine
- Clozapine + Deferiprone Contraindicated
- Clozapine + Irinotecan Contraindicated
- Clozapine + Pimozide Contraindicated
- Clozapine + Thioridazine Contraindicated
- Acalabrutinib + Clozapine Major
- Adagrasib + Clozapine Major
Frequently asked questions
Can I take Clozapine with Fesoterodine?
MediHelp rates the interaction as major. Clozapine and Fesoterodine can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Clozapine is strongly anticholinergic, and adding fesoterodine increases the risk of constipation, which with clozapine can progress to serious gastrointestinal hypomotility or ileus. Urinary retention, tachycardia and delirium may also occur.
How serious is the interaction between Clozapine and Fesoterodine?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination if possible; if used, monitor bowel function closely, treat constipation proactively, and review for alternatives such as a non-antimuscarinic bladder agent.
What other medicines interact with Fesoterodine?
MediHelp also lists interactions of Fesoterodine with, for example, Bethanechol, Levoketoconazole, Pramlintide. The full list is on the Fesoterodine page.
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