Drug interactions
Darifenacin + Diphenhydramine
Severity: Moderate
Darifenacin and Diphenhydramine: 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 is a strongly anticholinergic first-generation antihistamine. With darifenacin it increases the likelihood of dry mouth, constipation, urinary retention, blurred vision and confusion, especially in older adults.
What this interaction means in plain words
Darifenacin and Diphenhydramine 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.
Darifenacin belongs to Genitourinary; Diphenhydramine belongs to Respiratory.
Why it happens
Additive antimuscarinic pharmacodynamic effects.
What to do
Avoid regular use in older patients and consider a non-sedating second-generation antihistamine. Monitor for anticholinergic effects.
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 Darifenacin
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Darifenacin with Diphenhydramine?
MediHelp rates the interaction as moderate. Darifenacin and Diphenhydramine 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 is a strongly anticholinergic first-generation antihistamine. With darifenacin it increases the likelihood of dry mouth, constipation, urinary retention, blurred vision and confusion, especially in older adults.
How serious is the interaction between Darifenacin and Diphenhydramine?
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 regular use in older patients and consider a non-sedating second-generation antihistamine. Monitor for anticholinergic effects.
What other medicines interact with Darifenacin?
MediHelp also lists interactions of Darifenacin with, for example, Atazanavir, Bethanechol, Clarithromycin. The full list is on the Darifenacin page.
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