Drug interactions
Diphenhydramine + Pyridostigmine
Severity: Moderate
Diphenhydramine and Pyridostigmine: 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
Diphenhydramine is a strongly anticholinergic antihistamine that can counteract the effects of pyridostigmine. It may mask cholinergic side effects or blunt therapeutic benefit, and sedation could be mistaken for myasthenic weakness.
What this interaction means in plain words
Diphenhydramine and Pyridostigmine 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; Pyridostigmine belongs to Central Nervous System.
Why it happens
Pharmacodynamic antagonism between muscarinic blockade and cholinesterase inhibition.
What to do
Monitor muscle strength and cholinergic symptoms, and consider a less anticholinergic second-generation 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 Pyridostigmine
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Pyridostigmine?
MediHelp rates the interaction as moderate. Diphenhydramine and Pyridostigmine 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 is a strongly anticholinergic antihistamine that can counteract the effects of pyridostigmine. It may mask cholinergic side effects or blunt therapeutic benefit, and sedation could be mistaken for myasthenic weakness.
How serious is the interaction between Diphenhydramine and Pyridostigmine?
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 muscle strength and cholinergic symptoms, and consider a less anticholinergic second-generation antihistamine.
What other medicines interact with Pyridostigmine?
MediHelp also lists interactions of Pyridostigmine with, for example, Echothiophate iodide, Huperzine a, Neostigmine. The full list is on the Pyridostigmine page.
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