Drug interactions
Benztropine + Diphenhydramine
Severity: Moderate
Benztropine 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 strong antimuscarinic effects, so together they raise the risk of anticholinergic toxicity. This may include confusion, delirium, urinary retention, constipation, blurred vision and tachycardia, especially in older adults.
What this interaction means in plain words
Benztropine 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.
Benztropine belongs to Central Nervous System; Diphenhydramine belongs to Respiratory.
Why it happens
Additive muscarinic receptor antagonism and sedation.
What to do
Avoid routine combined use in older patients and monitor for cognitive and anticholinergic effects. Choose a non-sedating, non-anticholinergic alternative 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 Benztropine
- Benztropine + Memantine-donepezil Major
- Abobotulinumtoxina + Benztropine Moderate
- Amantadine + Benztropine Moderate
- Amitriptyline + Benztropine Moderate
- Amoxapine + Benztropine Moderate
- Atropine iv / + Benztropine Moderate
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Benztropine with Diphenhydramine?
MediHelp rates the interaction as moderate. Benztropine 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 strong antimuscarinic effects, so together they raise the risk of anticholinergic toxicity. This may include confusion, delirium, urinary retention, constipation, blurred vision and tachycardia, especially in older adults.
How serious is the interaction between Benztropine 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 routine combined use in older patients and monitor for cognitive and anticholinergic effects. Choose a non-sedating, non-anticholinergic alternative where possible.
What other medicines interact with Benztropine?
MediHelp also lists interactions of Benztropine with, for example, Memantine-donepezil, Abobotulinumtoxina, Amantadine. The full list is on the Benztropine page.
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