Drug interactions
Siponimod + Thioridazine
Severity: Contraindicated
Siponimod and Thioridazine: contraindicated 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 can cause bradycardia and atrioventricular conduction delay at initiation, and thioridazine prolongs QTc. Bradycardia increases vulnerability to torsades de pointes. Siponimod labeling advises against use with QT-prolonging drugs. Thioridazine, a CYP2D6 substrate and inhibitor, is not expected to alter siponimod CYP2C9 metabolism meaningfully.
What this interaction means in plain words
Siponimod and Thioridazine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two.
Siponimod belongs to Central Nervous System; Thioridazine belongs to Central Nervous System.
Why it happens
Siponimod-induced heart rate slowing combined with thioridazine-induced QT prolongation increases torsades risk.
What to do
Avoid the combination; use a different antipsychotic. If it cannot be avoided, obtain cardiology advice and ECG monitoring at initiation.
What to ask your pharmacist
- Is there an alternative to one of these two medicines for me?
- If both are essential, who is monitoring me and how often?
- Which symptoms mean I should stop and seek help straight away?
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Other interactions of Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Other interactions of Siponimod
- Cladribine + Siponimod Contraindicated
- Fingolimod + Siponimod Contraindicated
- Fluconazole + Siponimod Contraindicated
- Influenza virus vaccine quadrivalent intranasal + Siponimod Contraindicated
- Ponesimod + Siponimod Contraindicated
- Adenovirus types 4 and 7 live + Siponimod Major
Frequently asked questions
Can I take Siponimod with Thioridazine?
MediHelp rates the interaction as contraindicated. Siponimod and Thioridazine are not normally used together. Taking them at the same time is expected to cause harm or make one of them unsafe, so a different medicine is usually chosen for one of the two. Siponimod can cause bradycardia and atrioventricular conduction delay at initiation, and thioridazine prolongs QTc. Bradycardia increases vulnerability to torsades de pointes. Siponimod labeling advises against use with QT-prolonging drugs. Thioridazine, a CYP2D6 substrate and inhibitor, is not expected to alter siponimod CYP2C9 metabolism meaningfully.
How serious is the interaction between Siponimod and Thioridazine?
MediHelp rates it contraindicated, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination; use a different antipsychotic. If it cannot be avoided, obtain cardiology advice and ECG monitoring at initiation.
What other medicines interact with Thioridazine?
MediHelp also lists interactions of Thioridazine with, for example, Abiraterone, Adagrasib, Amiodarone. The full list is on the Thioridazine page.
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