Drug interactions
Diphenhydramine + Pilocarpine
Severity: Moderate
Diphenhydramine and Pilocarpine: 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
Pilocarpine is a muscarinic agonist while diphenhydramine is an antimuscarinic, so each can reduce the effect of the other. Diphenhydramine may blunt pilocarpine's benefit on salivation, for example in dry mouth.
What this interaction means in plain words
Diphenhydramine and Pilocarpine 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; Pilocarpine belongs to Miscellaneous.
Why it happens
Pharmacodynamic antagonism at muscarinic receptors.
What to do
Avoid regular co-use where possible; if pilocarpine response is poor, review and stop the anticholinergic antihistamine.
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
Other interactions of Pilocarpine
- Amitriptyline + Pilocarpine Moderate
- Atenolol-chlorthalidone + Pilocarpine Moderate
- Atenolol + Pilocarpine Moderate
- Atropine + Pilocarpine Moderate
- Betaxolol + Pilocarpine Moderate
- Bethanechol + Pilocarpine Moderate
Frequently asked questions
Can I take Diphenhydramine with Pilocarpine?
MediHelp rates the interaction as moderate. Diphenhydramine and Pilocarpine 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. Pilocarpine is a muscarinic agonist while diphenhydramine is an antimuscarinic, so each can reduce the effect of the other. Diphenhydramine may blunt pilocarpine's benefit on salivation, for example in dry mouth.
How serious is the interaction between Diphenhydramine and Pilocarpine?
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 co-use where possible; if pilocarpine response is poor, review and stop the anticholinergic antihistamine.
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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