Drug interactions
Clonazepam + Diphenhydramine
Severity: Moderate
Clonazepam 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 causes marked sedation and anticholinergic effects, which add to the sedative and psychomotor impairment of clonazepam. Older patients face greater risk of confusion, falls and next-day impairment.
What this interaction means in plain words
Clonazepam 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.
Clonazepam belongs to Central Nervous System; Diphenhydramine belongs to Respiratory.
Why it happens
Additive CNS depression through H1 antagonism and GABA-A potentiation.
What to do
Avoid regular combined use in older adults and use a non-sedating antihistamine if one is needed. Monitor for oversedation and warn about 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 Clonazepam
- Calcium / magnesium / potassium / sodium oxybates + Clonazepam Contraindicated
- Clonazepam + Sodium oxybate Contraindicated
- Alfentanil + Clonazepam Major
- Alprazolam + Clonazepam Major
- Amobarbital + Clonazepam Major
- Belladonna and opium + Clonazepam Major
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Clonazepam with Diphenhydramine?
MediHelp rates the interaction as moderate. Clonazepam 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 causes marked sedation and anticholinergic effects, which add to the sedative and psychomotor impairment of clonazepam. Older patients face greater risk of confusion, falls and next-day impairment.
How serious is the interaction between Clonazepam 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 regular combined use in older adults and use a non-sedating antihistamine if one is needed. Monitor for oversedation and warn about driving.
What other medicines interact with Clonazepam?
MediHelp also lists interactions of Clonazepam with, for example, Calcium / magnesium / potassium / sodium oxybates, Sodium oxybate, Alfentanil. The full list is on the Clonazepam page.
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