Drug interactions
Formoterol + Thioridazine
Severity: Major
Formoterol and Thioridazine: major interaction.
Last updated Sources: US FDA label
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
Thioridazine causes marked, dose-related QT prolongation and torsades de pointes. Formoterol may add to QT effects and hypokalemia, further increasing the risk of fatal arrhythmia.
What this interaction means in plain words
Formoterol and Thioridazine 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.
Formoterol belongs to Respiratory; Thioridazine belongs to Central Nervous System.
Why it happens
Additive QT prolongation, with beta-agonist related hypokalemia.
What to do
Avoid the combination and choose an alternative antipsychotic or bronchodilator. If it cannot be avoided, monitor ECG and keep potassium and magnesium normal.
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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References
Other interactions of Formoterol
- Adagrasib + Formoterol Major
- Amiodarone + Formoterol Major
- Amisulpride + Formoterol Major
- Amitriptyline + Formoterol Major
- Amoxapine + Formoterol Major
- Arformoterol + Formoterol Major
Other interactions of Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Frequently asked questions
Can I take Formoterol with Thioridazine?
MediHelp rates the interaction as major. Formoterol and Thioridazine 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. Thioridazine causes marked, dose-related QT prolongation and torsades de pointes. Formoterol may add to QT effects and hypokalemia, further increasing the risk of fatal arrhythmia.
How serious is the interaction between Formoterol and Thioridazine?
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 the combination and choose an alternative antipsychotic or bronchodilator. If it cannot be avoided, monitor ECG and keep potassium and magnesium normal.
What other medicines interact with Formoterol?
MediHelp also lists interactions of Formoterol with, for example, Adagrasib, Amiodarone, Amisulpride. The full list is on the Formoterol page.
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