Drug interactions
Diphenhydramine + Metoprolol
Severity: Moderate
Diphenhydramine and Metoprolol: 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
Diphenhydramine inhibits CYP2D6 and can increase metoprolol concentrations, which may lead to greater bradycardia and hypotension. Effects are more notable with repeated dosing and in CYP2D6 extensive metabolizers.
What this interaction means in plain words
Diphenhydramine and Metoprolol 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.
Diphenhydramine belongs to Respiratory; Metoprolol belongs to Cardiovascular.
Why it happens
Diphenhydramine inhibition of CYP2D6-mediated metoprolol metabolism.
What to do
Monitor heart rate and blood pressure with regular diphenhydramine use, and reduce the metoprolol dose if needed. Consider a non-sedating antihistamine as an 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 Metoprolol
- Metoprolol + Thioridazine Contraindicated
- Amifostine + Metoprolol Major
- Amiodarone + Metoprolol Major
- Atenolol-chlorthalidone + Metoprolol Major
- Atenolol + Metoprolol Major
- Betaxolol + Metoprolol Major
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Metoprolol?
MediHelp rates the interaction as moderate. Diphenhydramine and Metoprolol 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. Diphenhydramine inhibits CYP2D6 and can increase metoprolol concentrations, which may lead to greater bradycardia and hypotension. Effects are more notable with repeated dosing and in CYP2D6 extensive metabolizers.
How serious is the interaction between Diphenhydramine and Metoprolol?
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 with regular diphenhydramine use, and reduce the metoprolol dose if needed. Consider a non-sedating antihistamine as an alternative.
What other medicines interact with Metoprolol?
MediHelp also lists interactions of Metoprolol with, for example, Thioridazine, Amifostine, Amiodarone. The full list is on the Metoprolol page.
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