198 / 222
198
EMR
EMT
AEMT
Paramedic
Extended
Diphenhydramine (Benadryl)
Action
Onset
Antihistamine
Onset < 15 min
Peak effect 1-4 hours
Indications
Allergic Reaction (Localized and Systemic) (Adult and Pediatric)
Extrapyramidal Side Effects
Adult Dose
25-50 mg slow IV/IO, or IM, repeat 25 mg after 10 minutes if no response (Max 50 mg total)
Pediatric Dose
1 mg/kg slow IV/IO, or IM, maximum 25 mg
Contraindications
Hypersensitivity, nursing mothers (unless life threatening reaction)
Adverse Reactions
Cardiovascular: Hypotension, headache, palpitations, tachycardia, premature heart contractions
CNS: Sedation, sleepiness, dizziness, fatigue, confusion, restlessness, excitation, nervousness, tremor,
irritability, blurred vision, vertigo, tinnitus, convulsions
Gastrointestinal: Nausea, vomiting, diarrhea
Respiratory: Thickening of bronchial secretions, tightness of chest and wheezing, nasal congestion
Precautions
Has atropine-like action and should be used with caution in patients with a history of bronchial asthma,
increased intraocular pressure, cardiovascular disease, or hypertension. Use caution with lower respiratory
disease, including asthma.
Considerations
Promethazine (Phenergan), Haldol, and Reglan may cause extrapyramidal side effects.
Diphenhydramine (Benadryl
®
)