Drug interactions
Siponimod + Tositumomab
Severity: Major
Siponimod and Tositumomab: major 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
Tositumomab is an anti-CD20 radioimmunotherapy that causes prolonged B-cell depletion and marrow suppression. With siponimod, the risk of serious infection may be increased for an extended period.
What this interaction means in plain words
Siponimod and Tositumomab can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Additive immunosuppression from B-cell depletion and radiation-induced myelosuppression plus S1P receptor-mediated lymphocyte sequestration.
What to do
Avoid concurrent use where possible and monitor blood counts and infection for months after tositumomab. Delay siponimod initiation until counts recover.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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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
Frequently asked questions
Can I take Siponimod with Tositumomab?
MediHelp rates the interaction as major. Siponimod and Tositumomab can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Tositumomab is an anti-CD20 radioimmunotherapy that causes prolonged B-cell depletion and marrow suppression. With siponimod, the risk of serious infection may be increased for an extended period.
How serious is the interaction between Siponimod and Tositumomab?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid concurrent use where possible and monitor blood counts and infection for months after tositumomab. Delay siponimod initiation until counts recover.
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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