Drug interactions
Diphenhydramine + Scopolamine
Severity: Moderate
Diphenhydramine and Scopolamine: 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 first-generation antihistamine with strong anticholinergic and sedative effects. With scopolamine, these effects add up and may cause confusion, delirium, marked drowsiness, urinary retention and constipation, especially in older people.
What this interaction means in plain words
Diphenhydramine and Scopolamine 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; Scopolamine belongs to Respiratory.
Why it happens
Additive central and peripheral muscarinic blockade and sedation.
What to do
Avoid combining in older adults. Otherwise monitor for sedation, confusion and urinary retention and use a non-sedating antihistamine if appropriate.
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 Scopolamine, 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 Scopolamine
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Scopolamine?
MediHelp rates the interaction as moderate. Diphenhydramine and Scopolamine 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 first-generation antihistamine with strong anticholinergic and sedative effects. With scopolamine, these effects add up and may cause confusion, delirium, marked drowsiness, urinary retention and constipation, especially in older people.
How serious is the interaction between Diphenhydramine and Scopolamine?
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 in older adults. Otherwise monitor for sedation, confusion and urinary retention and use a non-sedating antihistamine if appropriate.
What other medicines interact with Scopolamine?
MediHelp also lists interactions of Scopolamine with, for example, Benzhydrocodone / acetaminophen, Buprenorphine long-acting, Buprenorphine subdermal implant. The full list is on the Scopolamine 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.
