Drug interactions
Fosphenytoin + Silodosin
Severity: Moderate
Fosphenytoin and Silodosin: 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
Fosphenytoin is converted to phenytoin, a CYP3A4 inducer that may lower silodosin exposure and blunt its effect on urinary symptoms. The result is reduced efficacy rather than toxicity.
What this interaction means in plain words
Fosphenytoin and Silodosin 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.
Fosphenytoin belongs to Central Nervous System; Silodosin belongs to Genitourinary.
Why it happens
Phenytoin induces CYP3A4 (and possibly P-glycoprotein), increasing silodosin clearance.
What to do
Monitor urinary symptom control and consider alternative therapy if silodosin becomes ineffective; no contraindication applies.
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 Silodosin
- Atazanavir + Silodosin Contraindicated
- Conivaptan + Silodosin Contraindicated
- Darunavir + Silodosin Contraindicated
- Fosamprenavir + Silodosin Contraindicated
- Indinavir + Silodosin Contraindicated
- Itraconazole + Silodosin Contraindicated
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 Fosphenytoin with Silodosin?
MediHelp rates the interaction as moderate. Fosphenytoin and Silodosin 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. Fosphenytoin is converted to phenytoin, a CYP3A4 inducer that may lower silodosin exposure and blunt its effect on urinary symptoms. The result is reduced efficacy rather than toxicity.
How serious is the interaction between Fosphenytoin and Silodosin?
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 alternative therapy if silodosin becomes ineffective; no contraindication applies.
What other medicines interact with Silodosin?
MediHelp also lists interactions of Silodosin with, for example, Atazanavir, Conivaptan, Darunavir. The full list is on the Silodosin page.
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