Drug interactions
Amobarbital + Phenytoin
Severity: Moderate
Amobarbital 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 have unpredictable effects on phenytoin levels: induction may lower them, while competition for metabolism may raise them. Both drugs also cause CNS depression, so seizure control and toxicity can both be affected.
What this interaction means in plain words
Amobarbital 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.
Amobarbital belongs to Central Nervous System; Phenytoin belongs to Central Nervous System.
Why it happens
Variable CYP2C9/2C19 induction or competitive inhibition of phenytoin metabolism, plus additive CNS depression.
What to do
Monitor serum phenytoin concentrations when starting, changing or stopping amobarbital. Adjust the dose based on levels and clinical response.
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 Amobarbital
- Amobarbital + Calcium / magnesium / potassium / sodium oxybates Contraindicated
- Amobarbital + Doravirine Contraindicated
- Amobarbital + Elbasvir / grazoprevir Contraindicated
- Amobarbital + Isavuconazonium Contraindicated
- Amobarbital + Isocarboxazid Contraindicated
- Amobarbital + Lonafarnib Contraindicated
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 Amobarbital with Phenytoin?
MediHelp rates the interaction as moderate. Amobarbital 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 have unpredictable effects on phenytoin levels: induction may lower them, while competition for metabolism may raise them. Both drugs also cause CNS depression, so seizure control and toxicity can both be affected.
How serious is the interaction between Amobarbital 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 concentrations when starting, changing or stopping amobarbital. Adjust the dose based on levels and clinical response.
What other medicines interact with Amobarbital?
MediHelp also lists interactions of Amobarbital with, for example, Calcium / magnesium / potassium / sodium oxybates, Doravirine, Elbasvir / grazoprevir. The full list is on the Amobarbital page.
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