Drug interactions
Amlodipine + Phenytoin
Severity: Moderate
Amlodipine and Phenytoin: 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
Phenytoin may induce CYP3A4 and reduce amlodipine effect, while amlodipine has been reported to raise phenytoin levels only rarely. Because phenytoin has a narrow therapeutic index, any rise in concentration could cause nystagmus, ataxia or confusion.
What this interaction means in plain words
Amlodipine and Phenytoin 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; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces CYP3A4 and lowers amlodipine exposure; amlodipine may weakly alter phenytoin metabolism.
What to do
Monitor blood pressure for reduced amlodipine effect and check phenytoin concentrations when starting or stopping amlodipine. Adjust doses based on response and levels.
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 Phenytoin
- Artemether / lumefantrine + Phenytoin Contraindicated
- Bictegravir + Phenytoin Contraindicated
- Cabotegravir + Phenytoin Contraindicated
- Doravirine + Phenytoin Contraindicated
- Elbasvir / grazoprevir + Phenytoin Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Phenytoin Contraindicated
Frequently asked questions
Can I take Amlodipine with Phenytoin?
MediHelp rates the interaction as moderate. Amlodipine and Phenytoin 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. Phenytoin may induce CYP3A4 and reduce amlodipine effect, while amlodipine has been reported to raise phenytoin levels only rarely. Because phenytoin has a narrow therapeutic index, any rise in concentration could cause nystagmus, ataxia or confusion.
How serious is the interaction between Amlodipine and Phenytoin?
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 for reduced amlodipine effect and check phenytoin concentrations when starting or stopping amlodipine. Adjust doses based on response and levels.
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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