Drug interactions
Thioridazine + Timolol
Severity: Major
Thioridazine and Timolol: 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 inhibits CYP2D6 and may raise timolol levels, and the combination can cause bradycardia and hypotension. Bradycardia increases the risk of torsades de pointes with thioridazine, which strongly prolongs the QT interval.
What this interaction means in plain words
Thioridazine and Timolol 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 belongs to Central Nervous System; Timolol belongs to Cardiovascular.
Why it happens
CYP2D6 inhibition reduces timolol clearance, with additive bradycardia and hypotension that heighten QT-related arrhythmia risk.
What to do
Avoid the combination if possible, or monitor heart rate, ECG and QTc closely and reduce the timolol dose. Correct potassium and magnesium abnormalities.
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 Timolol
- Acebutolol + Timolol Major
- Albuterol + Timolol Major
- Aldesleukin + Timolol Major
- Amifostine + Timolol Major
- Amiodarone + Timolol Major
- Arformoterol + Timolol 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 Thioridazine with Timolol?
MediHelp rates the interaction as major. Thioridazine and Timolol 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 inhibits CYP2D6 and may raise timolol levels, and the combination can cause bradycardia and hypotension. Bradycardia increases the risk of torsades de pointes with thioridazine, which strongly prolongs the QT interval.
How serious is the interaction between Thioridazine and Timolol?
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 if possible, or monitor heart rate, ECG and QTc closely and reduce the timolol dose. Correct potassium and magnesium abnormalities.
What other medicines interact with Timolol?
MediHelp also lists interactions of Timolol with, for example, Acebutolol, Albuterol, Aldesleukin. The full list is on the Timolol page.
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