Drug interactions
Felodipine + Fosphenytoin
Severity: Major
Felodipine and Fosphenytoin: major 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 strong enzyme inducer that substantially lowers felodipine concentrations. Blood pressure or angina control may be lost.
What this interaction means in plain words
Felodipine and Fosphenytoin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Felodipine belongs to Cardiovascular; Fosphenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4, greatly increasing felodipine clearance.
What to do
Avoid the combination if possible and use an antihypertensive not dependent on CYP3A4. If used, monitor blood pressure closely and increase the felodipine dose as needed.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Felodipine and Fosphenytoin, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 14 days on the web. No card needed.
Other interactions of Felodipine
- Felodipine + Itraconazole Contraindicated
- Aldesleukin + Felodipine Major
- Amifostine + Felodipine Major
- Apalutamide + Felodipine Major
- Atazanavir + Felodipine Major
- Carbamazepine + Felodipine Major
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 Felodipine with Fosphenytoin?
MediHelp rates the interaction as major. Felodipine and Fosphenytoin can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Fosphenytoin is converted to phenytoin, a strong enzyme inducer that substantially lowers felodipine concentrations. Blood pressure or angina control may be lost.
How serious is the interaction between Felodipine and Fosphenytoin?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination if possible and use an antihypertensive not dependent on CYP3A4. If used, monitor blood pressure closely and increase the felodipine dose as needed.
What other medicines interact with Felodipine?
MediHelp also lists interactions of Felodipine with, for example, Itraconazole, Aldesleukin, Amifostine. The full list is on the Felodipine page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
