Drug interactions
Amlodipine + Fosphenytoin
Severity: Moderate
Amlodipine 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
Fosphenytoin is converted to phenytoin, a CYP3A4 inducer that may lower amlodipine concentrations. Blood pressure control may deteriorate after it is started.
What this interaction means in plain words
Amlodipine 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.
Amlodipine belongs to Cardiovascular; Fosphenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4, increasing amlodipine clearance.
What to do
Monitor blood pressure after starting or stopping fosphenytoin, and increase the amlodipine dose if needed.
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 Amlodipine
- Amifostine + Amlodipine Major
- Amlodipine + Ombitasvir / paritaprevir / ritonavir and dasabuvir Major
- Activated Charcoal + Amlodipine Moderate
- Aldesleukin + Amlodipine Moderate
- Alfuzosin + Amlodipine Moderate
- Amlodipine + Apalutamide Moderate
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 Amlodipine with Fosphenytoin?
MediHelp rates the interaction as moderate. Amlodipine 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. Fosphenytoin is converted to phenytoin, a CYP3A4 inducer that may lower amlodipine concentrations. Blood pressure control may deteriorate after it is started.
How serious is the interaction between Amlodipine 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 blood pressure after starting or stopping fosphenytoin, and increase the amlodipine dose if needed.
What other medicines interact with Amlodipine?
MediHelp also lists interactions of Amlodipine with, for example, Amifostine, Ombitasvir / paritaprevir / ritonavir and dasabuvir, Activated Charcoal. The full list is on the Amlodipine page.
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