Drug interactions
Diphenhydramine + Propantheline
Severity: Moderate
Diphenhydramine and Propantheline: 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 agents are antimuscarinic, so using them together increases dry mouth, constipation, urinary retention, blurred vision and tachycardia. Confusion and heat intolerance can occur, particularly in older people.
What this interaction means in plain words
Diphenhydramine and Propantheline 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 muscarinic receptor blockade.
What to do
Avoid combining where an alternative exists, such as a non-sedating antihistamine. If used together, monitor for urinary retention, ileus and cognitive 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 Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Propantheline?
MediHelp rates the interaction as moderate. Diphenhydramine and Propantheline 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 agents are antimuscarinic, so using them together increases dry mouth, constipation, urinary retention, blurred vision and tachycardia. Confusion and heat intolerance can occur, particularly in older people.
How serious is the interaction between Diphenhydramine and Propantheline?
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 an alternative exists, such as a non-sedating antihistamine. If used together, monitor for urinary retention, ileus and cognitive effects.
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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