Drug interactions
Ethosuximide + Fosphenytoin
Severity: Moderate
Ethosuximide and Fosphenytoin: 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, the active form of fosphenytoin, induces hepatic enzymes and may lower ethosuximide levels. Ethosuximide may also alter phenytoin levels in some patients.
What this interaction means in plain words
Ethosuximide and Fosphenytoin 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.
Ethosuximide belongs to Central Nervous System; Fosphenytoin belongs to Central Nervous System.
Why it happens
Enzyme induction by phenytoin increases ethosuximide metabolism.
What to do
Monitor seizure control and serum levels of both drugs when either is started, changed or stopped. Adjust the ethosuximide dose as required.
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 Ethosuximide
- Benzhydrocodone / acetaminophen + Ethosuximide Major
- Buprenorphine long-acting + Ethosuximide Major
- Buprenorphine subdermal implant + Ethosuximide Major
- Buprenorphine transdermal + Ethosuximide Major
- Calcium / magnesium / potassium / sodium oxybates + Ethosuximide Major
- Ethosuximide + Fentanyl intranasal Major
Other interactions of Fosphenytoin
- Dronedarone + Fosphenytoin Contraindicated
- Fosphenytoin + Ledipasvir-sofosbuvir Contraindicated
- Fosphenytoin + Lorlatinib Contraindicated
- Fosphenytoin + Lurasidone Contraindicated
- Fosphenytoin + Ranolazine Contraindicated
- Fosphenytoin + Sofosbuvir-velpatasvir-voxilaprevir Contraindicated
Frequently asked questions
Can I take Ethosuximide with Fosphenytoin?
MediHelp rates the interaction as moderate. Ethosuximide and Fosphenytoin 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, the active form of fosphenytoin, induces hepatic enzymes and may lower ethosuximide levels. Ethosuximide may also alter phenytoin levels in some patients.
How serious is the interaction between Ethosuximide and Fosphenytoin?
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 seizure control and serum levels of both drugs when either is started, changed or stopped. Adjust the ethosuximide dose as required.
What other medicines interact with Ethosuximide?
MediHelp also lists interactions of Ethosuximide with, for example, Benzhydrocodone / acetaminophen, Buprenorphine long-acting, Buprenorphine subdermal implant. The full list is on the Ethosuximide page.
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