Drug interactions
Lacosamide + Phenytoin
Severity: Moderate
Lacosamide 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
Both drugs act on sodium channels and can slow cardiac conduction. Together they may increase the risk of PR prolongation, AV block, bradycardia or arrhythmia, especially in patients with conduction disease or heart disease. Lacosamide concentrations are not meaningfully changed.
What this interaction means in plain words
Lacosamide 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.
Lacosamide belongs to Central Nervous System; Phenytoin belongs to Central Nervous System.
Why it happens
Additive sodium channel blockade slows cardiac conduction.
What to do
Obtain a baseline ECG and repeat it once lacosamide is at steady state. Use particular care in patients with conduction abnormalities or other PR-prolonging drugs.
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
Other interactions of Lacosamide
- Lacosamide + Zuranolone Major
- Atazanavir + Lacosamide Moderate
- Carbamazepine + Lacosamide Moderate
- Cenobamate + Lacosamide Moderate
- Clarithromycin + Lacosamide Moderate
- Daridorexant + Lacosamide Moderate
Frequently asked questions
Can I take Lacosamide with Phenytoin?
MediHelp rates the interaction as moderate. Lacosamide 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. Both drugs act on sodium channels and can slow cardiac conduction. Together they may increase the risk of PR prolongation, AV block, bradycardia or arrhythmia, especially in patients with conduction disease or heart disease. Lacosamide concentrations are not meaningfully changed.
How serious is the interaction between Lacosamide 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: Obtain a baseline ECG and repeat it once lacosamide is at steady state. Use particular care in patients with conduction abnormalities or other PR-prolonging drugs.
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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