Drug interactions
Diphenhydramine + Oxybutynin transdermal
Severity: Moderate
Diphenhydramine and Oxybutynin transdermal: 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 drugs have antimuscarinic activity, so combined use can add to anticholinergic effects such as dry mouth, constipation, urinary retention, blurred vision, confusion and tachycardia. Older adults and patients with cognitive impairment are at greatest risk.
What this interaction means in plain words
Diphenhydramine and Oxybutynin transdermal 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
Additive blockade of muscarinic receptors by two anticholinergic agents.
What to do
Avoid combining where possible, especially in older patients, and prefer a non-anticholinergic antihistamine. If used together, monitor for confusion, urinary retention and constipation.
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 Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Oxybutynin transdermal?
MediHelp rates the interaction as moderate. Diphenhydramine and Oxybutynin transdermal 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 drugs have antimuscarinic activity, so combined use can add to anticholinergic effects such as dry mouth, constipation, urinary retention, blurred vision, confusion and tachycardia. Older adults and patients with cognitive impairment are at greatest risk.
How serious is the interaction between Diphenhydramine and Oxybutynin transdermal?
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 combining where possible, especially in older patients, and prefer a non-anticholinergic antihistamine. If used together, monitor for confusion, urinary retention and constipation.
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.
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