Drug interactions
Isradipine + Phenytoin
Severity: Moderate
Isradipine 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 is a strong inducer of CYP3A4 and can markedly reduce isradipine concentrations. This may lead to loss of blood pressure control or antianginal effect.
What this interaction means in plain words
Isradipine 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.
Why it happens
Phenytoin induces CYP3A4, increasing first-pass and systemic metabolism of isradipine.
What to do
Monitor blood pressure and heart rate and increase the isradipine dose if needed, or choose an alternative antihypertensive. Reassess the dose if phenytoin is discontinued.
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 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 Isradipine with Phenytoin?
MediHelp rates the interaction as moderate. Isradipine 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 is a strong inducer of CYP3A4 and can markedly reduce isradipine concentrations. This may lead to loss of blood pressure control or antianginal effect.
How serious is the interaction between Isradipine 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 and heart rate and increase the isradipine dose if needed, or choose an alternative antihypertensive. Reassess the dose if phenytoin is discontinued.
What other medicines interact with Phenytoin?
MediHelp also lists interactions of Phenytoin with, for example, Artemether / lumefantrine, Bictegravir, Cabotegravir. The full list is on the Phenytoin page.
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