Drug interactions
Fexofenadine + Fosphenytoin
Severity: Minor
Fexofenadine 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 P-glycoprotein and may lower fexofenadine concentrations. Reduced antihistamine effect is possible but typically not clinically important.
What this interaction means in plain words
Fexofenadine 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.
Fexofenadine belongs to Respiratory; Fosphenytoin belongs to Central Nervous System.
Why it happens
Induction of intestinal P-gp efflux by phenytoin, reducing fexofenadine absorption.
What to do
No routine action is needed; if allergy symptoms are poorly controlled, consider increasing monitoring or changing antihistamine.
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 Fexofenadine
- Danicopan + Fexofenadine Moderate
- Erdafitinib + Fexofenadine Moderate
- Fexofenadine + Glecaprevir / pibrentasvir Moderate
- Fexofenadine + Grapefruit Moderate
- Fexofenadine + Juice Moderate
- Acrivastine + Fexofenadine 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 Fexofenadine with Fosphenytoin?
MediHelp rates the interaction as minor. Fexofenadine 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 P-glycoprotein and may lower fexofenadine concentrations. Reduced antihistamine effect is possible but typically not clinically important.
How serious is the interaction between Fexofenadine 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 action is needed; if allergy symptoms are poorly controlled, consider increasing monitoring or changing antihistamine.
What other medicines interact with Fexofenadine?
MediHelp also lists interactions of Fexofenadine with, for example, Danicopan, Erdafitinib, Glecaprevir / pibrentasvir. The full list is on the Fexofenadine page.
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