Drug interactions
Chlorpromazine + Diphenhydramine
Severity: Moderate
Chlorpromazine 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
Both drugs are sedating with strong anticholinergic activity. Together they can cause heavy sedation, confusion, dry mouth, urinary retention, constipation and impaired thermoregulation, particularly in older adults.
What this interaction means in plain words
Chlorpromazine 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.
Chlorpromazine belongs to Central Nervous System; Diphenhydramine belongs to Respiratory.
Why it happens
Additive H1 blockade, CNS depression and muscarinic antagonism.
What to do
Avoid unnecessary combination, especially in the elderly; use a non-sedating alternative. Monitor for oversedation and anticholinergic toxicity.
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 Chlorpromazine
- Chlorpromazine + Dofetilide Contraindicated
- Chlorpromazine + Dronedarone Contraindicated
- Chlorpromazine + Droperidol Contraindicated
- Chlorpromazine + Ibutilide Contraindicated
- Chlorpromazine + Metrizamide Contraindicated
- Chlorpromazine + Panobinostat Contraindicated
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Chlorpromazine with Diphenhydramine?
MediHelp rates the interaction as moderate. Chlorpromazine 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. Both drugs are sedating with strong anticholinergic activity. Together they can cause heavy sedation, confusion, dry mouth, urinary retention, constipation and impaired thermoregulation, particularly in older adults.
How serious is the interaction between Chlorpromazine 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 unnecessary combination, especially in the elderly; use a non-sedating alternative. Monitor for oversedation and anticholinergic toxicity.
What other medicines interact with Chlorpromazine?
MediHelp also lists interactions of Chlorpromazine with, for example, Dofetilide, Dronedarone, Droperidol. The full list is on the Chlorpromazine page.
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