diphenhydramine
Adjunctive therapy • Brands: BENADRYL
Last reviewed: 2026-02-12
General information
- Primary label indications include: Allergy symptoms (OTC labeling varies).
- Class: Adjunctive therapy
- Common US brands: BENADRYL
- Therapeutic drug monitoring not routinely recommended.
- Last reviewed: 2026-02-12
Dosing & forms
- Forms/strengths: —
- Frequency: —
- Food: —
- Typical range: —
Mechanism (brief)
First-generation antihistamine (H1 antagonist) with sedating and anticholinergic effects; commonly used OTC for allergies and as a sleep aid.
Metabolism & Half‑life
- Metabolism: CYP2D6
- Half‑life: Single-dose mean 9 h
Therapeutic Drug Monitoring (TDM)
Recommended: No
Monitoring highlights
- —
Sources
- Benadryl (diphenhydramine) tablets (OTC) label — DailyMed (2026)
- Diphenhydramine (StatPearls) — StatPearls Publishing (NCBI Bookshelf) (2025)
- Clinical Practice Guideline for the Pharmacologic Treatment of Chronic Insomnia in Adults: An American Academy of Sleep Medicine Clinical Practice Guideline — Journal of Clinical Sleep Medicine (2017)
- 2023 American Geriatrics Society Updated Beers Criteria for Potentially Inappropriate Medication Use in Older Adults — Journal of the American Geriatrics Society (2023)