Drug interactions
Diphenhydramine + Lorazepam
Severity: Moderate
Diphenhydramine and Lorazepam: 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 a first-generation sedating antihistamine, and with lorazepam it produces additive sedation and psychomotor impairment. Confusion, falls and respiratory depression are more likely in older or frail patients.
What this interaction means in plain words
Diphenhydramine and Lorazepam 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; Lorazepam belongs to Central Nervous System.
Why it happens
Additive CNS depression from GABA-A potentiation by lorazepam and central H1 antagonism with anticholinergic effects from diphenhydramine.
What to do
Use the lowest effective doses and counsel on driving and alcohol. Avoid the combination in elderly patients or consider a non-sedating antihistamine.
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 Lorazepam
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Lorazepam?
MediHelp rates the interaction as moderate. Diphenhydramine and Lorazepam 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 a first-generation sedating antihistamine, and with lorazepam it produces additive sedation and psychomotor impairment. Confusion, falls and respiratory depression are more likely in older or frail patients.
How serious is the interaction between Diphenhydramine and Lorazepam?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Use the lowest effective doses and counsel on driving and alcohol. Avoid the combination in elderly patients or consider a non-sedating antihistamine.
What other medicines interact with Lorazepam?
MediHelp also lists interactions of Lorazepam with, for example, Alfentanil, Alprazolam, Amobarbital. The full list is on the Lorazepam page.
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