Drug interactions
Fosphenytoin + Midazolam
Severity: Moderate
Fosphenytoin and Midazolam: 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
Fosphenytoin is converted to phenytoin, which induces CYP3A4 and can lower midazolam exposure. Sedative or anticonvulsant effect of midazolam may be reduced, particularly after oral administration.
What this interaction means in plain words
Fosphenytoin and Midazolam 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.
Fosphenytoin belongs to Central Nervous System; Midazolam belongs to Central Nervous System.
Why it happens
Phenytoin induction of CYP3A4 increases midazolam clearance and first-pass metabolism.
What to do
Titrate midazolam to clinical effect, anticipating higher dose requirements, and consider an alternative benzodiazepine not dependent on CYP3A4 if effect is inadequate.
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 Midazolam
- Atazanavir + Midazolam Contraindicated
- Cobicistat + Midazolam Contraindicated
- Darunavir + Midazolam Contraindicated
- Elvitegravir / cobicistat / emtricitabine / tenofovir df + Midazolam Contraindicated
- Fosamprenavir + Midazolam Contraindicated
- Indinavir + Midazolam Contraindicated
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 Fosphenytoin with Midazolam?
MediHelp rates the interaction as moderate. Fosphenytoin and Midazolam 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. Fosphenytoin is converted to phenytoin, which induces CYP3A4 and can lower midazolam exposure. Sedative or anticonvulsant effect of midazolam may be reduced, particularly after oral administration.
How serious is the interaction between Fosphenytoin and Midazolam?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Titrate midazolam to clinical effect, anticipating higher dose requirements, and consider an alternative benzodiazepine not dependent on CYP3A4 if effect is inadequate.
What other medicines interact with Midazolam?
MediHelp also lists interactions of Midazolam with, for example, Atazanavir, Cobicistat, Darunavir. The full list is on the Midazolam page.
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