Drug interactions
Diphenhydramine + Metoclopramide
Severity: Moderate
Diphenhydramine and Metoclopramide: 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 sedating and a CYP2D6 inhibitor, which may raise metoclopramide exposure, while both drugs cause drowsiness. Its anticholinergic effects can also oppose metoclopramide's prokinetic action.
What this interaction means in plain words
Diphenhydramine and Metoclopramide 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; Metoclopramide belongs to Gastrointestinal Tract.
Why it happens
Additive central nervous system depression and CYP2D6 inhibition by diphenhydramine reducing metoclopramide clearance.
What to do
Monitor for sedation and extrapyramidal symptoms, and use the lowest effective doses. Diphenhydramine is sometimes used to treat metoclopramide dystonia, in which case administer it under observation.
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 Metoclopramide
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Metoclopramide?
MediHelp rates the interaction as moderate. Diphenhydramine and Metoclopramide 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 sedating and a CYP2D6 inhibitor, which may raise metoclopramide exposure, while both drugs cause drowsiness. Its anticholinergic effects can also oppose metoclopramide's prokinetic action.
How serious is the interaction between Diphenhydramine and Metoclopramide?
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 sedation and extrapyramidal symptoms, and use the lowest effective doses. Diphenhydramine is sometimes used to treat metoclopramide dystonia, in which case administer it under observation.
What other medicines interact with Metoclopramide?
MediHelp also lists interactions of Metoclopramide with, for example, Amantadine, Amoxapine, Antipsychotics (e.g., haloperidol). The full list is on the Metoclopramide page.
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