Drug interactions
Fosphenytoin + Ustekinumab
Severity: Minor
Fosphenytoin and Ustekinumab: minor 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
Chronic inflammation suppresses some CYP450 enzymes through cytokines, and IL-12/23 blockade may restore their activity. This could lower levels of narrow-therapeutic-index CYP substrates such as phenytoin, the active form of fosphenytoin. Clinical evidence is limited.
What this interaction means in plain words
Fosphenytoin and Ustekinumab have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Fosphenytoin belongs to Central Nervous System; Ustekinumab belongs to Gastrointestinal Tract.
Why it happens
Cytokine modulation by ustekinumab may normalize suppressed CYP450 expression and increase metabolism of phenytoin.
What to do
Check phenytoin levels and seizure control when ustekinumab is started or stopped, and adjust the dose as needed.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Fosphenytoin and Ustekinumab, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Ustekinumab
- Bcg vaccine live + Ustekinumab Contraindicated
- Typhoid vaccine live + Ustekinumab Contraindicated
- Adalimumab + Ustekinumab Major
- Adenovirus types 4 and 7 live + Ustekinumab Major
- Alefacept + Ustekinumab Major
- Anakinra + Ustekinumab Major
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 Ustekinumab?
MediHelp rates the interaction as minor. Fosphenytoin and Ustekinumab have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Chronic inflammation suppresses some CYP450 enzymes through cytokines, and IL-12/23 blockade may restore their activity. This could lower levels of narrow-therapeutic-index CYP substrates such as phenytoin, the active form of fosphenytoin. Clinical evidence is limited.
How serious is the interaction between Fosphenytoin and Ustekinumab?
MediHelp rates it minor, 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 when ustekinumab is started or stopped, and adjust the dose as needed.
What other medicines interact with Ustekinumab?
MediHelp also lists interactions of Ustekinumab with, for example, Bcg vaccine live, Typhoid vaccine live, Adalimumab. The full list is on the Ustekinumab page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
