Drug interactions
Metyrapone + Phenytoin
Severity: Moderate
Metyrapone 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
Phenytoin may lower metyrapone concentrations and reduce its effect on cortisol synthesis, which can distort diagnostic testing or weaken treatment of hypercortisolism. Metyrapone may also affect phenytoin levels.
What this interaction means in plain words
Metyrapone 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.
Metyrapone belongs to Endocrine; Phenytoin belongs to Central Nervous System.
Why it happens
Phenytoin induces hepatic metabolism of metyrapone, reducing its exposure.
What to do
Avoid using metyrapone for diagnostic testing in patients on phenytoin where possible. In treatment, monitor cortisol response and adjust the dose accordingly.
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 Metyrapone
- Metyrapone + Pacritinib Major
- Budesonide + Metyrapone Moderate
- Cortisone + Metyrapone Moderate
- Cyproheptadine + Metyrapone Moderate
- Deflazacort + Metyrapone Moderate
- Desogestrel-ethinyl estradiol + Metyrapone Moderate
Frequently asked questions
Can I take Metyrapone with Phenytoin?
MediHelp rates the interaction as moderate. Metyrapone 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. Phenytoin may lower metyrapone concentrations and reduce its effect on cortisol synthesis, which can distort diagnostic testing or weaken treatment of hypercortisolism. Metyrapone may also affect phenytoin levels.
How serious is the interaction between Metyrapone 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: Avoid using metyrapone for diagnostic testing in patients on phenytoin where possible. In treatment, monitor cortisol response and adjust the dose accordingly.
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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