Drug interactions
Cyclizine + Diphenhydramine
Severity: Moderate
Cyclizine 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 are first-generation antihistamines with sedative and anticholinergic effects. Combined use increases drowsiness, impaired psychomotor performance, dry mouth, urinary retention and confusion.
What this interaction means in plain words
Cyclizine 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.
Cyclizine belongs to Respiratory; Diphenhydramine belongs to Respiratory.
Why it happens
Additive central H1-receptor antagonism and muscarinic blockade.
What to do
Avoid concurrent use and keep to one sedating antihistamine. Monitor older patients for confusion 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 Cyclizine
- Calcium / magnesium / potassium / sodium oxybates + Cyclizine Major
- Cyclizine + Henbane Major
- Cyclizine + Sodium oxybate Major
- Abobotulinumtoxina + Cyclizine Moderate
- Alfentanil + Cyclizine Moderate
- Alprazolam + Cyclizine Moderate
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Cyclizine with Diphenhydramine?
MediHelp rates the interaction as moderate. Cyclizine 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 are first-generation antihistamines with sedative and anticholinergic effects. Combined use increases drowsiness, impaired psychomotor performance, dry mouth, urinary retention and confusion.
How serious is the interaction between Cyclizine 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 concurrent use and keep to one sedating antihistamine. Monitor older patients for confusion and anticholinergic toxicity.
What other medicines interact with Cyclizine?
MediHelp also lists interactions of Cyclizine with, for example, Calcium / magnesium / potassium / sodium oxybates, Henbane, Sodium oxybate. The full list is on the Cyclizine page.
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