Drug interactions
Diphenhydramine + Oxybutynin
Severity: Moderate
Diphenhydramine and Oxybutynin: 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, sedating antihistamine. Together with oxybutynin it can produce marked dry mouth, constipation, urinary retention, confusion and delirium, particularly in the elderly.
What this interaction means in plain words
Diphenhydramine and Oxybutynin 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; Oxybutynin belongs to Genitourinary.
Why it happens
Additive antimuscarinic effects with central nervous system penetration.
What to do
Avoid in older adults and those with cognitive impairment; use a non-sedating antihistamine instead. Monitor for retention and confusion if the combination is necessary.
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 Oxybutynin
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Oxybutynin?
MediHelp rates the interaction as moderate. Diphenhydramine and Oxybutynin 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, sedating antihistamine. Together with oxybutynin it can produce marked dry mouth, constipation, urinary retention, confusion and delirium, particularly in the elderly.
How serious is the interaction between Diphenhydramine and Oxybutynin?
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 in older adults and those with cognitive impairment; use a non-sedating antihistamine instead. Monitor for retention and confusion if the combination is necessary.
What other medicines interact with Oxybutynin?
MediHelp also lists interactions of Oxybutynin with, for example, Bethanechol, Clozapine, Potassium chloride. The full list is on the Oxybutynin page.
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