Drug interactions
Fesoterodine + Thioridazine
Severity: Major
Fesoterodine and Thioridazine: 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
Thioridazine has strong anticholinergic activity, so combined use markedly increases risk of dry mouth, constipation, urinary retention, confusion and tachycardia. Thioridazine is also a CYP2D6 substrate and inhibitor with a risk of QT prolongation.
What this interaction means in plain words
Fesoterodine and Thioridazine 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.
Fesoterodine belongs to Genitourinary; Thioridazine belongs to Central Nervous System.
Why it happens
Additive antimuscarinic effects, with thioridazine's CYP2D6 inhibition potentially raising fesoterodine metabolite levels.
What to do
Avoid the combination where possible, particularly in elderly patients. If unavoidable, monitor for anticholinergic toxicity and ECG changes.
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 Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Frequently asked questions
Can I take Fesoterodine with Thioridazine?
MediHelp rates the interaction as major. Fesoterodine and Thioridazine 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. Thioridazine has strong anticholinergic activity, so combined use markedly increases risk of dry mouth, constipation, urinary retention, confusion and tachycardia. Thioridazine is also a CYP2D6 substrate and inhibitor with a risk of QT prolongation.
How serious is the interaction between Fesoterodine and Thioridazine?
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 where possible, particularly in elderly patients. If unavoidable, monitor for anticholinergic toxicity and ECG changes.
What other medicines interact with Fesoterodine?
MediHelp also lists interactions of Fesoterodine with, for example, Bethanechol, Clozapine, Levoketoconazole. The full list is on the Fesoterodine page.
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