Drug interactions
Diphenhydramine + Orphenadrin
Severity: Moderate
Diphenhydramine and Orphenadrin: 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
Orphenadrine is structurally related to diphenhydramine and both are strongly anticholinergic and sedating. Combined use can cause marked drowsiness, confusion, dry mouth, constipation, urinary retention, tachycardia and, in older adults, delirium.
What this interaction means in plain words
Diphenhydramine and Orphenadrin 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; Orphenadrin belongs to Musculoskeletal.
Why it happens
Additive antimuscarinic and central H1-antihistaminic effects.
What to do
Avoid concurrent use in older or cognitively impaired patients and choose a non-anticholinergic alternative for allergy or sleep. If unavoidable, use the lowest doses and monitor for sedation and anticholinergic toxicity.
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 Orphenadrin
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Orphenadrin?
MediHelp rates the interaction as moderate. Diphenhydramine and Orphenadrin 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. Orphenadrine is structurally related to diphenhydramine and both are strongly anticholinergic and sedating. Combined use can cause marked drowsiness, confusion, dry mouth, constipation, urinary retention, tachycardia and, in older adults, delirium.
How serious is the interaction between Diphenhydramine and Orphenadrin?
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 concurrent use in older or cognitively impaired patients and choose a non-anticholinergic alternative for allergy or sleep. If unavoidable, use the lowest doses and monitor for sedation and anticholinergic toxicity.
What other medicines interact with Orphenadrin?
MediHelp also lists interactions of Orphenadrin with, for example, Alfentanil, Amobarbital, Benzhydrocodone / acetaminophen. The full list is on the Orphenadrin page.
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