Drug interactions
Amantadine + Diphenhydramine
Severity: Moderate
Amantadine 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
Both drugs have anticholinergic activity, so combining them can add to dry mouth, blurred vision, urinary retention, constipation, sedation and confusion. The risk of delirium is higher in older adults.
What this interaction means in plain words
Amantadine 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.
Amantadine belongs to Anti Virals; Diphenhydramine belongs to Respiratory.
Why it happens
Additive anticholinergic pharmacodynamic effects.
What to do
Monitor for confusion, urinary retention and constipation, particularly in elderly patients. Prefer a non-sedating, non-anticholinergic antihistamine where possible.
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 Amantadine
- Amantadine + Ethanol Major
- Amantadine + Memantine-donepezil Major
- Amantadine + Metoclopramide Major
- Amantadine + Metoclopramide intranasal Major
- Amantadine + Amifampridine Moderate
- Amantadine + Amisulpride Moderate
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Amantadine with Diphenhydramine?
MediHelp rates the interaction as moderate. Amantadine 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. Both drugs have anticholinergic activity, so combining them can add to dry mouth, blurred vision, urinary retention, constipation, sedation and confusion. The risk of delirium is higher in older adults.
How serious is the interaction between Amantadine 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: Monitor for confusion, urinary retention and constipation, particularly in elderly patients. Prefer a non-sedating, non-anticholinergic antihistamine where possible.
What other medicines interact with Amantadine?
MediHelp also lists interactions of Amantadine with, for example, Ethanol, Memantine-donepezil, Metoclopramide. The full list is on the Amantadine page.
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