Drug interactions
Pentobarbital + Phenytoin
Severity: Moderate
Pentobarbital 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
Barbiturates can induce phenytoin metabolism, but they may also compete for it, so the effect on phenytoin levels is unpredictable. Additive CNS depression also occurs.
What this interaction means in plain words
Pentobarbital 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.
Why it happens
Barbiturate enzyme induction or competitive metabolism alters phenytoin clearance, with additive CNS depression.
What to do
Monitor phenytoin levels and sedation when pentobarbital is started or stopped, and adjust the phenytoin dose according to levels.
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
Frequently asked questions
Can I take Pentobarbital with Phenytoin?
MediHelp rates the interaction as moderate. Pentobarbital 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. Barbiturates can induce phenytoin metabolism, but they may also compete for it, so the effect on phenytoin levels is unpredictable. Additive CNS depression also occurs.
How serious is the interaction between Pentobarbital 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 phenytoin levels and sedation when pentobarbital is started or stopped, and adjust the phenytoin dose according to levels.
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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