Drug interactions
Quinidine + Timolol
Severity: Moderate
Quinidine and Timolol: 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
Quinidine inhibits CYP2D6, which metabolizes timolol, and can raise systemic timolol levels, with excess beta-blockade such as bradycardia and hypotension. This applies to oral timolol and to eye drops, where systemic absorption is enough to cause bradycardia in susceptible patients.
What this interaction means in plain words
Quinidine and Timolol 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.
Quinidine belongs to Anti Parasitic; Timolol belongs to Cardiovascular.
Why it happens
Quinidine inhibits CYP2D6-mediated metabolism of timolol, increasing systemic exposure.
What to do
Monitor heart rate and blood pressure, and reduce the timolol dose if bradycardia or hypotension occurs. Consider a non-CYP2D6-dependent alternative.
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 Quinidine
- Adagrasib + Quinidine Contraindicated
- Arsenic trioxide + Quinidine Contraindicated
- Artemether / lumefantrine + Quinidine Contraindicated
- Chloroquine + Quinidine Contraindicated
- Dofetilide + Quinidine Contraindicated
- Dronedarone + Quinidine Contraindicated
Other interactions of Timolol
- Acebutolol + Timolol Major
- Albuterol + Timolol Major
- Aldesleukin + Timolol Major
- Amifostine + Timolol Major
- Amiodarone + Timolol Major
- Arformoterol + Timolol Major
Frequently asked questions
Can I take Quinidine with Timolol?
MediHelp rates the interaction as moderate. Quinidine and Timolol 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. Quinidine inhibits CYP2D6, which metabolizes timolol, and can raise systemic timolol levels, with excess beta-blockade such as bradycardia and hypotension. This applies to oral timolol and to eye drops, where systemic absorption is enough to cause bradycardia in susceptible patients.
How serious is the interaction between Quinidine and Timolol?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor heart rate and blood pressure, and reduce the timolol dose if bradycardia or hypotension occurs. Consider a non-CYP2D6-dependent alternative.
What other medicines interact with Quinidine?
MediHelp also lists interactions of Quinidine with, for example, Adagrasib, Arsenic trioxide, Artemether / lumefantrine. The full list is on the Quinidine page.
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