Diphenhydramine

GENERIC NAME

Diphenhydramine

TRADE NAME

Benadryl

DESCRIPTION

Diphenhydramine is a potent antihistamine with both antihistamine and mild sedative properties.

HOW SUPPLIED

Ampule and pre-filled syringe: 50 mg/mL

INDICATIONS

• Anaphylaxis
• Allergic reactions

CONTRAINDICATIONS

• Allergy or hypersensitivity to diphenhydramine

MECHANISM OF ACTION

1. Blocks the effects of histamine, preventing bronchoconstriction and vasodilation.
2. Produces mild sedative effects.

SIDE EFFECTS

• Hypotension
• Headache
• Palpitations
• Tachycardia
• Sedation and drowsiness
• Disturbed coordination

AUTHORIZATION

EMT: Not authorized

AEMT: Standing order (IM only)

Paramedic: Standing order

DOSAGE

• Adult:
  • 25 mg, slow IV/IO push or IM for mild allergic reaction
  • 50 mg, slow IV/IO push or IM for severe allergic reaction
• Pediatric:
  • 1 mg/kg, slow IV/IO push or IM (max dose 25 mg) for mild or moderate reaction
  • 1 mg/kg, slow IV/IO push or IM (max dose 50 mg) for severe reaction