Drug interactions
Isoproterenol + Timolol
Severity: Major
Isoproterenol and Timolol: major interaction.
Last updated Sources: UK SmPC
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
Timolol blocks beta-1 and beta-2 receptors and directly antagonizes isoproterenol, reducing its cardiac stimulation and bronchodilation. Isoproterenol may be ineffective for bradycardia or bronchospasm in a beta-blocked patient, and higher doses may be needed.
What this interaction means in plain words
Isoproterenol 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.
Isoproterenol belongs to Respiratory; Timolol belongs to Cardiovascular.
Why it happens
Competitive antagonism at beta-adrenergic receptors.
What to do
Monitor heart rate, blood pressure and respiratory status and titrate isoproterenol to effect. Consider alternative agents such as atropine, glucagon or pacing for beta-blocker-related bradycardia.
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 Timolol
- Acebutolol + Timolol Major
- Aldesleukin + Timolol Major
- Amifostine + Timolol Major
- Amiodarone + Timolol Major
- Arformoterol + Timolol Major
- Atenolol-chlorthalidone + Timolol Major
Other interactions of Isoproterenol
Frequently asked questions
Can I take Isoproterenol with Timolol?
MediHelp rates the interaction as major. Isoproterenol 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. Timolol blocks beta-1 and beta-2 receptors and directly antagonizes isoproterenol, reducing its cardiac stimulation and bronchodilation. Isoproterenol may be ineffective for bradycardia or bronchospasm in a beta-blocked patient, and higher doses may be needed.
How serious is the interaction between Isoproterenol 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: Monitor heart rate, blood pressure and respiratory status and titrate isoproterenol to effect. Consider alternative agents such as atropine, glucagon or pacing for beta-blocker-related bradycardia.
What other medicines interact with Timolol?
MediHelp also lists interactions of Timolol with, for example, Acebutolol, Aldesleukin, Amifostine. The full list is on the Timolol page.
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