Drug interactions
Diphenhydramine + Opium tincture
Severity: Major
Diphenhydramine and Opium tincture: major interaction.
Last updated Sources: US FDA label
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
Opium tincture contains morphine, and combining it with a sedating antihistamine increases drowsiness and the risk of respiratory depression. Anticholinergic effects may also worsen constipation and urinary retention.
What this interaction means in plain words
Diphenhydramine and Opium tincture can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Additive CNS and respiratory depression, with additive antimuscarinic effects.
What to do
Avoid the combination where possible, or use the lowest effective doses and monitor sedation and respiratory rate. Counsel against alcohol and driving.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Opium tincture?
MediHelp rates the interaction as major. Diphenhydramine and Opium tincture can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Opium tincture contains morphine, and combining it with a sedating antihistamine increases drowsiness and the risk of respiratory depression. Anticholinergic effects may also worsen constipation and urinary retention.
How serious is the interaction between Diphenhydramine and Opium tincture?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid the combination where possible, or use the lowest effective doses and monitor sedation and respiratory rate. Counsel against alcohol and driving.
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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