Drug interactions
Fosphenytoin + Guselkumab
Severity: Minor
Fosphenytoin and Guselkumab: 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 raises cytokines such as IL-6 that suppress CYP450 expression, and IL-23 blockade may reverse this suppression. Metabolism of CYP substrates such as phenytoin could therefore shift once guselkumab is started or stopped. Phenytoin has a narrow therapeutic index, so small changes in exposure matter.
What this interaction means in plain words
Fosphenytoin and Guselkumab 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; Guselkumab belongs to Miscellaneous.
Why it happens
Cytokine modulation by IL-23 inhibition may normalize suppressed CYP450 enzyme activity, potentially altering phenytoin clearance.
What to do
When starting or stopping guselkumab, check phenytoin levels and clinical response (seizure control, toxicity). Adjust the fosphenytoin dose only if levels or effect change.
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?
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Other interactions of Guselkumab
- Adenovirus types 4 and 7 live + Guselkumab Major
- Bcg vaccine live + Guselkumab Major
- Guselkumab + Influenza virus vaccine quadrivalent intranasal Major
- Guselkumab + Measles mumps and rubella vaccine live Major
- Guselkumab + Measles mumps rubella and varicella vaccine live Major
- Guselkumab + Measles vaccine 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 Guselkumab?
MediHelp rates the interaction as minor. Fosphenytoin and Guselkumab 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 raises cytokines such as IL-6 that suppress CYP450 expression, and IL-23 blockade may reverse this suppression. Metabolism of CYP substrates such as phenytoin could therefore shift once guselkumab is started or stopped. Phenytoin has a narrow therapeutic index, so small changes in exposure matter.
How serious is the interaction between Fosphenytoin and Guselkumab?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: When starting or stopping guselkumab, check phenytoin levels and clinical response (seizure control, toxicity). Adjust the fosphenytoin dose only if levels or effect change.
What other medicines interact with Guselkumab?
MediHelp also lists interactions of Guselkumab with, for example, Adenovirus types 4 and 7 live, Bcg vaccine live, Influenza virus vaccine quadrivalent intranasal. The full list is on the Guselkumab page.
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