Drug interactions
Dimenhydrinate + Diphenhydramine
Severity: Moderate
Dimenhydrinate and Diphenhydramine: 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
Dimenhydrinate is a salt of diphenhydramine with 8-chlorotheophylline, so combining it with diphenhydramine duplicates the same active antihistamine. This risks excess sedation, anticholinergic toxicity and confusion.
What this interaction means in plain words
Dimenhydrinate and Diphenhydramine 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.
Dimenhydrinate belongs to Respiratory; Diphenhydramine belongs to Respiratory.
Why it happens
Therapeutic duplication leading to additive H1 and muscarinic receptor blockade.
What to do
Avoid the combination and use only one product. Check over-the-counter sleep and allergy products for hidden diphenhydramine.
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 Dimenhydrinate
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Dimenhydrinate with Diphenhydramine?
MediHelp rates the interaction as moderate. Dimenhydrinate and Diphenhydramine 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. Dimenhydrinate is a salt of diphenhydramine with 8-chlorotheophylline, so combining it with diphenhydramine duplicates the same active antihistamine. This risks excess sedation, anticholinergic toxicity and confusion.
How serious is the interaction between Dimenhydrinate and Diphenhydramine?
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 the combination and use only one product. Check over-the-counter sleep and allergy products for hidden diphenhydramine.
What other medicines interact with Dimenhydrinate?
MediHelp also lists interactions of Dimenhydrinate with, for example, Belladonna and opium, Brexanolone, Calcium / magnesium / potassium / sodium oxybates. The full list is on the Dimenhydrinate page.
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