Drug interactions
Isoniazid + Siponimod
Severity: Moderate
Isoniazid 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
Siponimod is cleared by CYP2C9 and, to a lesser degree, CYP3A4. Isoniazid can inhibit CYP3A4 and also CYP2C9 to some extent, so siponimod exposure could rise. The combined effect on both pathways is not well characterised but could increase adverse effects such as bradyarrhythmia, infections and liver enzyme elevation.
What this interaction means in plain words
Isoniazid 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.
Isoniazid belongs to Anti Bacterial; Siponimod belongs to Central Nervous System.
Why it happens
Isoniazid may inhibit CYP3A4 and CYP2C9, reducing siponimod metabolism.
What to do
Check the patient's CYP2C9 genotype before siponimod, and avoid the combination in CYP2C9*3/*3 patients. Monitor heart rate, liver enzymes and lymphocyte counts.
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 Isoniazid
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 Isoniazid with Siponimod?
MediHelp rates the interaction as moderate. Isoniazid 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. Siponimod is cleared by CYP2C9 and, to a lesser degree, CYP3A4. Isoniazid can inhibit CYP3A4 and also CYP2C9 to some extent, so siponimod exposure could rise. The combined effect on both pathways is not well characterised but could increase adverse effects such as bradyarrhythmia, infections and liver enzyme elevation.
How serious is the interaction between Isoniazid 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: Check the patient's CYP2C9 genotype before siponimod, and avoid the combination in CYP2C9*3/*3 patients. Monitor heart rate, liver enzymes and lymphocyte counts.
What other medicines interact with Isoniazid?
MediHelp also lists interactions of Isoniazid with, for example, Bacillus calmette-guerin substrain tice, Benzhydrocodone / acetaminophen, Carbamazepine. The full list is on the Isoniazid page.
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