Drug interactions
Fosaprepitant + Siponimod
Severity: Moderate
Fosaprepitant and Siponimod: 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
Fosaprepitant is converted to aprepitant, a weak to moderate CYP3A4 inhibitor, particularly with multiple-day dosing. A single dose is likely to have only a small effect on siponimod, and the interaction matters mostly when CYP2C9 function is also reduced. Raised siponimod exposure could increase bradycardia and immunosuppression.
What this interaction means in plain words
Fosaprepitant and Siponimod 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.
Fosaprepitant belongs to Gastrointestinal Tract; Siponimod belongs to Central Nervous System.
Why it happens
Aprepitant inhibits CYP3A4, reducing one of the two main clearance pathways of siponimod.
What to do
A single fosaprepitant dose is generally acceptable; avoid repeated use in patients with CYP2C9*2/*3 or *3/*3 genotypes or those on a CYP2C9 inhibitor. Monitor heart rate and lymphocyte counts if used repeatedly.
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 Siponimod
- Cladribine + Siponimod Contraindicated
- Fingolimod + Siponimod Contraindicated
- Fluconazole + Siponimod Contraindicated
- Influenza virus vaccine quadrivalent intranasal + Siponimod Contraindicated
- Ponesimod + Siponimod Contraindicated
- Siponimod + Thioridazine Contraindicated
Other interactions of Fosaprepitant
- Flibanserin + Fosaprepitant Contraindicated
- Fosaprepitant + Pimozide Contraindicated
- Alprazolam + Fosaprepitant Moderate
- Amiodarone + Fosaprepitant Moderate
- Amobarbital + Fosaprepitant Moderate
- Apalutamide + Fosaprepitant Moderate
Frequently asked questions
Can I take Fosaprepitant with Siponimod?
MediHelp rates the interaction as moderate. Fosaprepitant and Siponimod 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. Fosaprepitant is converted to aprepitant, a weak to moderate CYP3A4 inhibitor, particularly with multiple-day dosing. A single dose is likely to have only a small effect on siponimod, and the interaction matters mostly when CYP2C9 function is also reduced. Raised siponimod exposure could increase bradycardia and immunosuppression.
How serious is the interaction between Fosaprepitant and Siponimod?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: A single fosaprepitant dose is generally acceptable; avoid repeated use in patients with CYP2C9*2/*3 or *3/*3 genotypes or those on a CYP2C9 inhibitor. Monitor heart rate and lymphocyte counts if used repeatedly.
What other medicines interact with Siponimod?
MediHelp also lists interactions of Siponimod with, for example, Cladribine, Fingolimod, Fluconazole. The full list is on the Siponimod page.
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