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Diphenhydramine

Brand: Benadryl

Antihistamine (1st-gen)Used for: Allergies, sleep aidRespiratory & Allergy

No boxed warning on the current FDA label.

Caution
Strongly anticholinergic and sedating: avoid in older adults (Beers list) and in narrow-angle glaucoma, urinary retention, or prostate enlargement.

Common side effects

  • Drowsiness
  • Dry mouth
  • Dizziness
  • Constipation
  • Blurred vision

Key interactions

  • Alcohol increases sedation
  • Adds to other sedating drugs
  • Adds to other anticholinergic drugs

Counseling points

  • May cause marked drowsiness
  • Do not drive until you know its effect
  • Avoid alcohol
  • Use caution in older adults
  • Avoid with narrow-angle glaucoma
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High-yield study aid for exam prep, not a substitute for the package insert or a pharmacist’s dispensing reference.