Drug interactions
Pseudoephedrine + Thioridazine
Severity: Major
Pseudoephedrine and Thioridazine: 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
Thioridazine markedly prolongs the QT interval and carries a risk of torsades de pointes, and sympathomimetic stimulation can add to arrhythmic risk. Combining them may increase the chance of serious ventricular arrhythmia.
What this interaction means in plain words
Pseudoephedrine 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.
Pseudoephedrine belongs to Respiratory; Thioridazine belongs to Central Nervous System.
Why it happens
Additive pharmacodynamic arrhythmogenic effects: thioridazine QT prolongation with adrenergic cardiac stimulation.
What to do
Avoid pseudoephedrine in patients taking thioridazine; if unavoidable, monitor ECG and electrolytes and correct potassium and magnesium.
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 Pseudoephedrine
- Isocarboxazid + Pseudoephedrine Contraindicated
- Phenelzine + Pseudoephedrine Contraindicated
- Pseudoephedrine + Rasagiline Contraindicated
- Pseudoephedrine + Selegiline Contraindicated
- Pseudoephedrine + Selegiline transdermal Contraindicated
- Pseudoephedrine + Tranylcypromine Contraindicated
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 Pseudoephedrine with Thioridazine?
MediHelp rates the interaction as major. Pseudoephedrine 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 markedly prolongs the QT interval and carries a risk of torsades de pointes, and sympathomimetic stimulation can add to arrhythmic risk. Combining them may increase the chance of serious ventricular arrhythmia.
How serious is the interaction between Pseudoephedrine 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 pseudoephedrine in patients taking thioridazine; if unavoidable, monitor ECG and electrolytes and correct potassium and magnesium.
What other medicines interact with Pseudoephedrine?
MediHelp also lists interactions of Pseudoephedrine with, for example, Isocarboxazid, Phenelzine, Rasagiline. The full list is on the Pseudoephedrine page.
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