Drug interactions
Diphenhydramine + Neostigmine
Severity: Minor
Diphenhydramine and Neostigmine: minor 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
Diphenhydramine's anticholinergic properties can counteract the muscarinic effects of neostigmine. Its clinical effect on neostigmine efficacy is usually modest.
What this interaction means in plain words
Diphenhydramine and Neostigmine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Diphenhydramine belongs to Respiratory; Neostigmine belongs to Central Nervous System.
Why it happens
Muscarinic antagonism by diphenhydramine opposes the increased acetylcholine from cholinesterase inhibition.
What to do
Monitor response to neostigmine, especially in myasthenia gravis, and avoid unnecessary anticholinergic antihistamines.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Neostigmine
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Neostigmine?
MediHelp rates the interaction as minor. Diphenhydramine and Neostigmine have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Diphenhydramine's anticholinergic properties can counteract the muscarinic effects of neostigmine. Its clinical effect on neostigmine efficacy is usually modest.
How serious is the interaction between Diphenhydramine and Neostigmine?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor response to neostigmine, especially in myasthenia gravis, and avoid unnecessary anticholinergic antihistamines.
What other medicines interact with Neostigmine?
MediHelp also lists interactions of Neostigmine with, for example, Huperzine a, Physostigmine, Pyridostigmine. The full list is on the Neostigmine page.
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