Drug interactions
Mexiletine + Phenytoin
Severity: Moderate
Mexiletine 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 induces hepatic enzymes and shortens mexiletine half-life, lowering its concentrations. This can lead to loss of antiarrhythmic or analgesic effect.
What this interaction means in plain words
Mexiletine 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.
Mexiletine belongs to Cardiovascular; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces hepatic CYP-mediated metabolism of mexiletine.
What to do
Monitor clinical response and ECG or arrhythmia control, and consider a mexiletine dose increase. Reassess the dose if 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 Mexiletine
- Fezolinetant + Mexiletine Contraindicated
- Mexiletine + Pimozide Contraindicated
- Alosetron + Mexiletine Major
- Amiodarone + Mexiletine Major
- Clozapine + Mexiletine Major
- Cobicistat + Mexiletine Major
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 Mexiletine with Phenytoin?
MediHelp rates the interaction as moderate. Mexiletine 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 induces hepatic enzymes and shortens mexiletine half-life, lowering its concentrations. This can lead to loss of antiarrhythmic or analgesic effect.
How serious is the interaction between Mexiletine 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 clinical response and ECG or arrhythmia control, and consider a mexiletine dose increase. Reassess the dose if phenytoin is stopped.
What other medicines interact with Mexiletine?
MediHelp also lists interactions of Mexiletine with, for example, Fezolinetant, Pimozide, Alosetron. The full list is on the Mexiletine page.
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