Drug interactions
Dutasteride + Fosphenytoin
Severity: Minor
Dutasteride and Fosphenytoin: minor 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 may lower dutasteride exposure. This may reduce dutasteride efficacy with prolonged therapy.
What this interaction means in plain words
Dutasteride and Fosphenytoin have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Dutasteride belongs to Genitourinary; Fosphenytoin belongs to Central Nervous System.
Why it happens
Induction of CYP3A4 by phenytoin increases dutasteride metabolic clearance.
What to do
No routine dose change is needed. Reassess dutasteride response if symptoms persist during prolonged anticonvulsant therapy.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Dutasteride
- Dutasteride + Levoketoconazole Moderate
- Dutasteride + Nefazodone Moderate
- Dutasteride + Rifampin Moderate
- Dutasteride + St john's wort Moderate
- Amobarbital + Dutasteride Minor
- Aprepitant + Dutasteride Minor
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 Dutasteride with Fosphenytoin?
MediHelp rates the interaction as minor. Dutasteride and Fosphenytoin have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Phenytoin, the active form of fosphenytoin, induces CYP3A4 and may lower dutasteride exposure. This may reduce dutasteride efficacy with prolonged therapy.
How serious is the interaction between Dutasteride and Fosphenytoin?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No routine dose change is needed. Reassess dutasteride response if symptoms persist during prolonged anticonvulsant therapy.
What other medicines interact with Dutasteride?
MediHelp also lists interactions of Dutasteride with, for example, Levoketoconazole, Nefazodone, Rifampin. The full list is on the Dutasteride page.
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