Drug interactions
Diphenhydramine + Tiotropium
Severity: Moderate
Diphenhydramine and Tiotropium: 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 activity that adds to tiotropium. Sedation, confusion, dry mouth, urinary retention and constipation may be amplified, especially in older adults.
What this interaction means in plain words
Diphenhydramine and Tiotropium 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; Tiotropium belongs to Respiratory.
Why it happens
Additive muscarinic receptor antagonism.
What to do
Avoid regular diphenhydramine use in elderly patients; consider a second-generation antihistamine. Monitor for cognitive and urinary 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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Diphenhydramine and Tiotropium, 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 Tiotropium
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Tiotropium?
MediHelp rates the interaction as moderate. Diphenhydramine and Tiotropium 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 activity that adds to tiotropium. Sedation, confusion, dry mouth, urinary retention and constipation may be amplified, especially in older adults.
How serious is the interaction between Diphenhydramine and Tiotropium?
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 diphenhydramine use in elderly patients; consider a second-generation antihistamine. Monitor for cognitive and urinary effects.
What other medicines interact with Tiotropium?
MediHelp also lists interactions of Tiotropium with, for example, Glycopyrrolate inhaled, Indacaterol-glycopyrronium, Revefenacin. The full list is on the Tiotropium 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.
