Drug interactions
Phenobarbital + Timolol
Severity: Moderate
Phenobarbital 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
Phenobarbital is a potent enzyme inducer and can lower exposure to hepatically cleared beta-blockers such as timolol. This may weaken the intended effect on heart rate, blood pressure or angina.
What this interaction means in plain words
Phenobarbital 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.
Why it happens
Induction of hepatic CYP enzymes increases the metabolic clearance of timolol.
What to do
Monitor heart rate and blood pressure and raise the timolol dose if the response is inadequate; reassess the dose if phenobarbital is stopped.
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 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 Phenobarbital with Timolol?
MediHelp rates the interaction as moderate. Phenobarbital 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. Phenobarbital is a potent enzyme inducer and can lower exposure to hepatically cleared beta-blockers such as timolol. This may weaken the intended effect on heart rate, blood pressure or angina.
How serious is the interaction between Phenobarbital 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 raise the timolol dose if the response is inadequate; reassess the dose if phenobarbital is stopped.
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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