Page 116 - 2026 SMOG

DIPHENHYDRAMINE (BENADRYL)
Class/Mechanism of Action
• Histamine H 1 Antagonist
First-generation (sedating) antihistamine. Competes with histamine for H 1-receptor sites within
the gastrointestinal tract, blood vessels, and respiratory tract; Also produces anticholinergic and
sedative effects.
Indications
• Labeled Indications
˚ Allergic reaction, anaphylaxis, and anaphylactic shock
˚ Motion Sickness
˚ Antitussive
Contraindications
• Hypersensitivity to diphenhydramine or any component of the formulation
• Use on Neonates, premature infants, and nursing mothers
• Caution: Acute Asthma, CNS depression
Adverse Reactions/Precautions
• Normally causes sedation, but may cause paradoxical excitation in children
• Rapid IV infusion may precipitate seizures in pediatrics
• May cause sedation and respiratory depression, especially when used with other sedatives or
alcohol.
• May cause hypotension (use with caution in patients with cardiovascular disease)
• Anticholinergic effects
• Pregnancy: Category B
• Lactation: Unsafe
Dose/Administration
PEDIATRIC
ADULT
(Always reference Broselow Tape)
Allergic Reactions and Motion Sickness Anaphylaxis/Anaphylactic Shock
• PO • IV/IM/PO
˚ 25mg q4–6hr or 50mg q6–8hr ˚ 1–2mg/kg (max dose: 50mg)
• IM/IV Push Allergic Reaction (by age)
˚ 10–50mg once q6hr prn • Ages 2 to <6 years:
Anaphylaxis ˚ PO: 6.25mg q4–8hr
Note: Diphenhydramine is not the first-line • Ages ≥6 to <12 years:
medication for anaphylaxis ˚ PO: 12.5–25mg q4–8hr
• IV • Ages >12 years (adolescents):
˚
IV/IM/PO: 25–50mg/dose
˚ 25–50mg q4–6hr prn; administered after Motion Sickness
epinephrine
Acute Hemolytic Reaction (Rapid onset of • PO
itching, chills, flushing, nausea/vomiting, ˚ 0.5–1mg/kg q6hr
coughing, wheezing, laryngeal edema, dyspnea, • IV/IM
hypotension, hemoglobinuria, rise in venous ˚ 1.25mg/kg q6hr
pressure, distended neck veins, crackles in
lung bases)
• IV/IM
˚ 25mg once
108 • MEDICATIONS