Drug interactions
Fosphenytoin + Sarilumab
Severity: Moderate
Fosphenytoin and Sarilumab: 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
IL-6 blockade can restore CYP2C9 and CYP2C19 activity suppressed by inflammation, which may lower phenytoin levels. Phenytoin has a narrow therapeutic range, so seizure control could be affected.
What this interaction means in plain words
Fosphenytoin and Sarilumab 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; Sarilumab belongs to Musculoskeletal.
Why it happens
Sarilumab reverses IL-6-mediated CYP downregulation, increasing phenytoin metabolism.
What to do
Check phenytoin levels and seizure control after starting or stopping sarilumab and adjust the dose.
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 Sarilumab
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 Sarilumab?
MediHelp rates the interaction as moderate. Fosphenytoin and Sarilumab 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. IL-6 blockade can restore CYP2C9 and CYP2C19 activity suppressed by inflammation, which may lower phenytoin levels. Phenytoin has a narrow therapeutic range, so seizure control could be affected.
How serious is the interaction between Fosphenytoin and Sarilumab?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Check phenytoin levels and seizure control after starting or stopping sarilumab and adjust the dose.
What other medicines interact with Sarilumab?
MediHelp also lists interactions of Sarilumab with, for example, Adenovirus types 4 and 7 live, Bcg vaccine live, Dengue vaccine. The full list is on the Sarilumab page.
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