Drug interactions
Thioridazine + Trimethoprim
Severity: Moderate
Thioridazine and Trimethoprim: 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
Trimethoprim has been associated with QT prolongation in some reports, and thioridazine is strongly QT-prolonging. The combination may raise arrhythmia risk, mainly in patients with other risk factors.
What this interaction means in plain words
Thioridazine and Trimethoprim 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.
Thioridazine belongs to Central Nervous System; Trimethoprim belongs to Anti Bacterial.
Why it happens
Possible additive QTc prolongation.
What to do
Consider alternatives in patients with QT risk factors; otherwise monitor ECG and potassium, since trimethoprim can raise potassium.
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 Thioridazine
- Abiraterone + Thioridazine Contraindicated
- Adagrasib + Thioridazine Contraindicated
- Amiodarone + Thioridazine Contraindicated
- Amisulpride + Thioridazine Contraindicated
- Amitriptyline + Thioridazine Contraindicated
- Amoxapine + Thioridazine Contraindicated
Other interactions of Trimethoprim
Frequently asked questions
Can I take Thioridazine with Trimethoprim?
MediHelp rates the interaction as moderate. Thioridazine and Trimethoprim 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. Trimethoprim has been associated with QT prolongation in some reports, and thioridazine is strongly QT-prolonging. The combination may raise arrhythmia risk, mainly in patients with other risk factors.
How serious is the interaction between Thioridazine and Trimethoprim?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Consider alternatives in patients with QT risk factors; otherwise monitor ECG and potassium, since trimethoprim can raise potassium.
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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