Drug interactions
Fesoterodine + Phenytoin
Severity: Moderate
Fesoterodine and Phenytoin: moderate 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
Phenytoin induces CYP3A4 and can lower exposure to the active metabolite of fesoterodine. Reduced antimuscarinic effect may lead to inadequate symptom control.
What this interaction means in plain words
Fesoterodine and Phenytoin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Fesoterodine belongs to Genitourinary; Phenytoin belongs to Central Nervous System.
Why it happens
CYP3A4 induction by phenytoin increases clearance of the fesoterodine active metabolite.
What to do
Monitor bladder symptom control and increase the fesoterodine dose to the maximum labeled dose if needed. Consider an alternative if symptoms persist.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Fesoterodine
Other interactions of Phenytoin
- Artemether / lumefantrine + Phenytoin Contraindicated
- Bictegravir + Phenytoin Contraindicated
- Cabotegravir + Phenytoin Contraindicated
- Doravirine + Phenytoin Contraindicated
- Elbasvir / grazoprevir + Phenytoin Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Phenytoin Contraindicated
Frequently asked questions
Can I take Fesoterodine with Phenytoin?
MediHelp rates the interaction as moderate. Fesoterodine and Phenytoin can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Phenytoin induces CYP3A4 and can lower exposure to the active metabolite of fesoterodine. Reduced antimuscarinic effect may lead to inadequate symptom control.
How serious is the interaction between Fesoterodine and Phenytoin?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor bladder symptom control and increase the fesoterodine dose to the maximum labeled dose if needed. Consider an alternative if symptoms persist.
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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