Drug interactions
Methsuximide + Phenytoin
Severity: Moderate
Methsuximide 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
Methsuximide may raise phenytoin concentrations, with possible toxicity such as ataxia, nystagmus or sedation. Its active metabolite may also contribute to additive central nervous system effects.
What this interaction means in plain words
Methsuximide 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.
Methsuximide belongs to Central Nervous System; Phenytoin belongs to Central Nervous System.
Why it happens
Methsuximide and its metabolite may inhibit hepatic metabolism of phenytoin.
What to do
Monitor serum phenytoin levels and for signs of toxicity when methsuximide is added or changed, and reduce the phenytoin dose if needed.
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 Methsuximide
- Amisulpride + Methsuximide Moderate
- Amobarbital + Methsuximide Moderate
- Apalutamide + Methsuximide Moderate
- Asenapine + Methsuximide Moderate
- Brexpiprazole + Methsuximide Moderate
- Brivaracetam + Methsuximide Moderate
Frequently asked questions
Can I take Methsuximide with Phenytoin?
MediHelp rates the interaction as moderate. Methsuximide 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. Methsuximide may raise phenytoin concentrations, with possible toxicity such as ataxia, nystagmus or sedation. Its active metabolite may also contribute to additive central nervous system effects.
How serious is the interaction between Methsuximide 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 serum phenytoin levels and for signs of toxicity when methsuximide is added or changed, and reduce the phenytoin dose if needed.
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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