Drug interactions
Diphenhydramine + Fluphenazine
Severity: Moderate
Diphenhydramine and Fluphenazine: 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 and anticholinergic, so combined use can lead to marked drowsiness, confusion, dry mouth, constipation and urinary retention. Diphenhydramine is also sometimes used to treat fluphenazine extrapyramidal effects, in which case the combined anticholinergic burden should be watched.
What this interaction means in plain words
Diphenhydramine and Fluphenazine 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; Fluphenazine belongs to Central Nervous System.
Why it happens
Additive CNS depression and additive antimuscarinic and antihistaminic effects.
What to do
Monitor for oversedation and anticholinergic toxicity, especially in older adults, and use the lowest effective diphenhydramine dose. Prefer a non-sedating antihistamine for allergy.
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 Fluphenazine
- Arsenic trioxide + Fluphenazine Contraindicated
- Dofetilide + Fluphenazine Contraindicated
- Fluphenazine + Ibutilide Contraindicated
- Fluphenazine + Pimozide Contraindicated
- Adagrasib + Fluphenazine Major
- Alfentanil + Fluphenazine Major
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Fluphenazine?
MediHelp rates the interaction as moderate. Diphenhydramine and Fluphenazine 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 and anticholinergic, so combined use can lead to marked drowsiness, confusion, dry mouth, constipation and urinary retention. Diphenhydramine is also sometimes used to treat fluphenazine extrapyramidal effects, in which case the combined anticholinergic burden should be watched.
How serious is the interaction between Diphenhydramine and Fluphenazine?
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 for oversedation and anticholinergic toxicity, especially in older adults, and use the lowest effective diphenhydramine dose. Prefer a non-sedating antihistamine for allergy.
What other medicines interact with Fluphenazine?
MediHelp also lists interactions of Fluphenazine with, for example, Arsenic trioxide, Dofetilide, Ibutilide. The full list is on the Fluphenazine page.
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