Drug interactions
Diphenhydramine + Oxymorphone
Severity: Moderate
Diphenhydramine and Oxymorphone: 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 adds to opioid sedation and psychomotor impairment, and its anticholinergic effects can worsen constipation and urinary retention. Its CYP2D6 inhibition has little effect on oxymorphone, which is cleared mainly by glucuronidation.
What this interaction means in plain words
Diphenhydramine and Oxymorphone 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; Oxymorphone belongs to Musculoskeletal.
Why it happens
Additive CNS depression through H1 antagonism and opioid agonism; CYP2D6 inhibition is of minor relevance.
What to do
Monitor for oversedation and respiratory depression, particularly in older adults, and use the lowest effective doses. Prefer a non-sedating antihistamine where appropriate.
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 Oxymorphone
- Alvimopan + Oxymorphone Contraindicated
- Ethanol + Oxymorphone Contraindicated
- Isocarboxazid + Oxymorphone Contraindicated
- Olanzapine / samidorphan + Oxymorphone Contraindicated
- Oxymorphone + Phenelzine Contraindicated
- Oxymorphone + Selegiline transdermal Contraindicated
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Oxymorphone?
MediHelp rates the interaction as moderate. Diphenhydramine and Oxymorphone 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 adds to opioid sedation and psychomotor impairment, and its anticholinergic effects can worsen constipation and urinary retention. Its CYP2D6 inhibition has little effect on oxymorphone, which is cleared mainly by glucuronidation.
How serious is the interaction between Diphenhydramine and Oxymorphone?
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 oversedation and respiratory depression, particularly in older adults, and use the lowest effective doses. Prefer a non-sedating antihistamine where appropriate.
What other medicines interact with Oxymorphone?
MediHelp also lists interactions of Oxymorphone with, for example, Alvimopan, Ethanol, Isocarboxazid. The full list is on the Oxymorphone page.
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