Drug interactions
Diphenhydramine + Hyoscyamine spray
Severity: Moderate
Diphenhydramine and Hyoscyamine spray: 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 block muscarinic receptors, so combined use can add to dry mouth, constipation, urinary retention, blurred vision, tachycardia and confusion. Older adults and patients with glaucoma, prostatic hypertrophy or ileus are at greater risk.
What this interaction means in plain words
Diphenhydramine and Hyoscyamine spray 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.
Why it happens
Additive antimuscarinic (anticholinergic) pharmacodynamic effects.
What to do
Monitor for anticholinergic toxicity, especially in older patients, and avoid adding further anticholinergic drugs. Reduce the dose of one agent or choose a non-anticholinergic alternative if symptoms develop.
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
Frequently asked questions
Can I take Diphenhydramine with Hyoscyamine spray?
MediHelp rates the interaction as moderate. Diphenhydramine and Hyoscyamine spray 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 block muscarinic receptors, so combined use can add to dry mouth, constipation, urinary retention, blurred vision, tachycardia and confusion. Older adults and patients with glaucoma, prostatic hypertrophy or ileus are at greater risk.
How serious is the interaction between Diphenhydramine and Hyoscyamine spray?
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 anticholinergic toxicity, especially in older patients, and avoid adding further anticholinergic drugs. Reduce the dose of one agent or choose a non-anticholinergic alternative if symptoms develop.
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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