Drug interactions
Diazepam + Diphenhydramine
Severity: Moderate
Diazepam 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
Diphenhydramine is strongly sedating and adds to diazepam's CNS depressant effects. Impaired psychomotor performance, confusion and falls are more likely, especially in older adults.
What this interaction means in plain words
Diazepam 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 belongs to Musculoskeletal; Diphenhydramine belongs to Respiratory.
Why it happens
Additive CNS depression from H1-antihistamine and benzodiazepine GABA-A effects.
What to do
Avoid combining where possible, particularly in the elderly; if used, lower doses and counsel on sedation and driving.
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 Diazepam
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diazepam with Diphenhydramine?
MediHelp rates the interaction as moderate. Diazepam 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. Diphenhydramine is strongly sedating and adds to diazepam's CNS depressant effects. Impaired psychomotor performance, confusion and falls are more likely, especially in older adults.
How serious is the interaction between Diazepam 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: Avoid combining where possible, particularly in the elderly; if used, lower doses and counsel on sedation and driving.
What other medicines interact with Diazepam?
MediHelp also lists interactions of Diazepam with, for example, Calcium / magnesium / potassium / sodium oxybates, Alfentanil, Alprazolam. The full list is on the Diazepam page.
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