Drug interactions
Diphenhydramine + Dutasteride-tamsulosin
Severity: Moderate
Diphenhydramine and Dutasteride-tamsulosin: 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 a weak CYP2D6 inhibitor and may slightly increase tamsulosin levels. Its anticholinergic effects may also worsen urinary retention in men with prostatic enlargement, which counteracts the benefit of tamsulosin.
What this interaction means in plain words
Diphenhydramine and Dutasteride-tamsulosin 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; Dutasteride-tamsulosin belongs to Genitourinary.
Why it happens
Weak CYP2D6 inhibition plus opposing anticholinergic effect on bladder emptying.
What to do
Avoid diphenhydramine where possible in men with benign prostatic hyperplasia. Use a non-sedating antihistamine and monitor urinary flow if needed.
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 Dutasteride-tamsulosin
Other interactions of Diphenhydramine
Frequently asked questions
Can I take Diphenhydramine with Dutasteride-tamsulosin?
MediHelp rates the interaction as moderate. Diphenhydramine and Dutasteride-tamsulosin 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 a weak CYP2D6 inhibitor and may slightly increase tamsulosin levels. Its anticholinergic effects may also worsen urinary retention in men with prostatic enlargement, which counteracts the benefit of tamsulosin.
How serious is the interaction between Diphenhydramine and Dutasteride-tamsulosin?
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 diphenhydramine where possible in men with benign prostatic hyperplasia. Use a non-sedating antihistamine and monitor urinary flow if needed.
What other medicines interact with Dutasteride-tamsulosin?
MediHelp also lists interactions of Dutasteride-tamsulosin with, for example, Alfuzosin, Amifostine, Atazanavir. The full list is on the Dutasteride-tamsulosin page.
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