Drug interactions
Diazepam intranasal + Diphenhydramine
Severity: Moderate
Diazepam intranasal and Diphenhydramine: 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
Diazepam is a benzodiazepine, and diphenhydramine is a sedating antihistamine. Together they intensify drowsiness and psychomotor impairment and can add to respiratory depression. This matters most after a seizure rescue dose, when the patient is already sedated.
What this interaction means in plain words
Diazepam intranasal and Diphenhydramine 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 central nervous system depression from GABA-A potentiation and central H1 receptor blockade.
What to do
Monitor consciousness and breathing after diazepam dosing and avoid giving diphenhydramine at the same time unless needed. Counsel against driving and alcohol.
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 Diazepam intranasal with Diphenhydramine?
MediHelp rates the interaction as moderate. Diazepam intranasal and Diphenhydramine 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. Diazepam is a benzodiazepine, and diphenhydramine is a sedating antihistamine. Together they intensify drowsiness and psychomotor impairment and can add to respiratory depression. This matters most after a seizure rescue dose, when the patient is already sedated.
How serious is the interaction between Diazepam intranasal and Diphenhydramine?
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 consciousness and breathing after diazepam dosing and avoid giving diphenhydramine at the same time unless needed. Counsel against driving and alcohol.
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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