Drug interactions
Cyproheptadine + Diphenhydramine
Severity: Moderate
Cyproheptadine 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, so combining them duplicates therapy and increases drowsiness and anticholinergic effects such as dry mouth, urinary retention and confusion.
What this interaction means in plain words
Cyproheptadine 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.
Cyproheptadine belongs to Respiratory; Diphenhydramine belongs to Respiratory.
Why it happens
Additive H1 antagonism, CNS depression and anticholinergic activity.
What to do
Avoid duplicate antihistamine use, including over-the-counter diphenhydramine sleep or cold products, and monitor older patients for confusion and sedation.
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 Cyproheptadine
- Cyproheptadine + Isocarboxazid Contraindicated
- Cyproheptadine + Phenelzine Contraindicated
- Cyproheptadine + Tranylcypromine Contraindicated
- Alfentanil + Cyproheptadine Major
- Belladonna and opium + Cyproheptadine Major
- Benzhydrocodone / acetaminophen + Cyproheptadine Major
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Cyproheptadine with Diphenhydramine?
MediHelp rates the interaction as moderate. Cyproheptadine 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, so combining them duplicates therapy and increases drowsiness and anticholinergic effects such as dry mouth, urinary retention and confusion.
How serious is the interaction between Cyproheptadine 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 duplicate antihistamine use, including over-the-counter diphenhydramine sleep or cold products, and monitor older patients for confusion and sedation.
What other medicines interact with Cyproheptadine?
MediHelp also lists interactions of Cyproheptadine with, for example, Isocarboxazid, Phenelzine, Tranylcypromine. The full list is on the Cyproheptadine page.
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