Drug interactions
Diphenhydramine + Meclizine
Severity: Moderate
Diphenhydramine and Meclizine: 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
Both are sedating H1 antihistamines with antimuscarinic activity, so combining them increases drowsiness and anticholinergic effects such as dry mouth, blurred vision and urinary retention. Elderly patients are at greater risk of confusion and falls.
What this interaction means in plain words
Diphenhydramine and Meclizine 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; Meclizine belongs to Respiratory.
Why it happens
Additive central H1 blockade and peripheral and central muscarinic antagonism.
What to do
Avoid using both together; choose one agent and monitor for sedation and anticholinergic effects if overlap occurs.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Diphenhydramine and Meclizine, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
Other interactions of Diphenhydramine
Other interactions of Meclizine
Frequently asked questions
Can I take Diphenhydramine with Meclizine?
MediHelp rates the interaction as moderate. Diphenhydramine and Meclizine 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. Both are sedating H1 antihistamines with antimuscarinic activity, so combining them increases drowsiness and anticholinergic effects such as dry mouth, blurred vision and urinary retention. Elderly patients are at greater risk of confusion and falls.
How serious is the interaction between Diphenhydramine and Meclizine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid using both together; choose one agent and monitor for sedation and anticholinergic effects if overlap occurs.
What other medicines interact with Diphenhydramine?
MediHelp also lists interactions of Diphenhydramine with, for example, Alfentanil, Belladonna and opium, Benzhydrocodone / acetaminophen. The full list is on the Diphenhydramine page.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
