Drug interactions
Diphenhydramine + Trimipramine
Severity: Moderate
Diphenhydramine and Trimipramine: 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 strongly sedating and anticholinergic, so together they can cause pronounced drowsiness, confusion, urinary retention, constipation and tachycardia. The risk of delirium is greater in older patients.
What this interaction means in plain words
Diphenhydramine and Trimipramine 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; Trimipramine belongs to Central Nervous System.
Why it happens
Additive antimuscarinic and H1-antihistaminic effects; diphenhydramine also inhibits CYP2D6, which may raise tricyclic levels.
What to do
Avoid regular diphenhydramine use, especially in the elderly, and choose a non-sedating antihistamine. Monitor for oversedation and anticholinergic toxicity if it is used.
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 Trimipramine
- Disopyramide + Trimipramine Contraindicated
- Dofetilide + Trimipramine Contraindicated
- Ibutilide + Trimipramine Contraindicated
- Isocarboxazid + Trimipramine Contraindicated
- Pentamidine + Trimipramine Contraindicated
- Phenelzine + Trimipramine Contraindicated
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Trimipramine?
MediHelp rates the interaction as moderate. Diphenhydramine and Trimipramine 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 strongly sedating and anticholinergic, so together they can cause pronounced drowsiness, confusion, urinary retention, constipation and tachycardia. The risk of delirium is greater in older patients.
How serious is the interaction between Diphenhydramine and Trimipramine?
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 diphenhydramine use, especially in the elderly, and choose a non-sedating antihistamine. Monitor for oversedation and anticholinergic toxicity if it is used.
What other medicines interact with Trimipramine?
MediHelp also lists interactions of Trimipramine with, for example, Disopyramide, Dofetilide, Ibutilide. The full list is on the Trimipramine page.
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