Drug interactions
Fesoterodine + Fosphenytoin
Severity: Moderate
Fesoterodine and Fosphenytoin: 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, the active form of fosphenytoin, induces CYP3A4 and can lower exposure to the active metabolite of fesoterodine. This may reduce effectiveness for overactive bladder.
What this interaction means in plain words
Fesoterodine and Fosphenytoin 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; Fosphenytoin belongs to Central Nervous System.
Why it happens
Induction of CYP3A4 increases clearance of the active metabolite of fesoterodine.
What to do
Monitor urinary symptom control and consider increasing fesoterodine to the maximum labeled dose or choosing an alternative if the response is inadequate.
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 Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Fesoterodine with Fosphenytoin?
MediHelp rates the interaction as moderate. Fesoterodine and Fosphenytoin 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, the active form of fosphenytoin, induces CYP3A4 and can lower exposure to the active metabolite of fesoterodine. This may reduce effectiveness for overactive bladder.
How serious is the interaction between Fesoterodine and Fosphenytoin?
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 urinary symptom control and consider increasing fesoterodine to the maximum labeled dose or choosing an alternative if the response is inadequate.
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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