Drug interactions
Phenytoin + Propafenone
Severity: Moderate
Phenytoin and Propafenone: 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 CYP enzymes including CYP3A4 and may substantially lower propafenone levels. Loss of antiarrhythmic effect is possible. Both drugs also affect cardiac conduction.
What this interaction means in plain words
Phenytoin and Propafenone 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 belongs to Central Nervous System; Propafenone belongs to Cardiovascular.
Why it happens
Phenytoin induction of CYP3A4 and other CYP enzymes increasing propafenone clearance.
What to do
Monitor ECG and arrhythmia control, and increase propafenone dose if efficacy declines. Reassess dosing when phenytoin is stopped.
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 Propafenone
- Dofetilide + Propafenone Contraindicated
- Dronedarone + Propafenone Contraindicated
- Nilotinib + Propafenone Contraindicated
- Nirmatrelvir / ritonavir + Propafenone Contraindicated
- Nirmatrelvir + Propafenone Contraindicated
- Pimozide + Propafenone Contraindicated
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 Phenytoin with Propafenone?
MediHelp rates the interaction as moderate. Phenytoin and Propafenone 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 CYP enzymes including CYP3A4 and may substantially lower propafenone levels. Loss of antiarrhythmic effect is possible. Both drugs also affect cardiac conduction.
How serious is the interaction between Phenytoin and Propafenone?
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 ECG and arrhythmia control, and increase propafenone dose if efficacy declines. Reassess dosing when phenytoin is stopped.
What other medicines interact with Propafenone?
MediHelp also lists interactions of Propafenone with, for example, Dofetilide, Dronedarone, Nilotinib. The full list is on the Propafenone page.
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