Pediatric Diphenhydramine Dosing Guidelines

Standard Pediatric Dosing by Age and Weight

For children 6 to under 12 years, alternative weight-based dosing is 1-2 mg/kg per dose, maximum 50 mg, as recommended by the American Academy of Allergy, Asthma, and Immunology 1, 2
The maximum daily dose for children 6 to under 12 years is 6 doses in 24 hours, not to exceed 300 mg daily, according to the American Academy of Pediatrics 3

Liquid formulations are preferred over tablets for acute allergic reactions requiring rapid absorption, as stated by the American Academy of Allergy, Asthma, and Immunology 2, 3
The onset of action for oral diphenhydramine is 20-30 minutes, peak effect is 45-60 minutes, and duration is 4-6 hours, as reported by the American Academy of Pediatrics 4, 3

The American Academy of Allergy, Asthma, and Immunology recommends that diphenhydramine should never be used as monotherapy for anaphylaxis 3
For anaphylaxis treatment, the first-line therapy is epinephrine 0.01 mg/kg IM, followed by adjunctive therapy with diphenhydramine 1-2 mg/kg (maximum 50 mg) IV or oral, as recommended by the American Academy of Allergy, Asthma, and Immunology 1, 2

For chemical restraint for agitation in children aged 6-12 years, the American Academy of Pediatrics recommends combination therapy with haloperidol 0.1 mg/kg PO/IM/IV + diphenhydramine 0.1 mg/kg PO/IM/IV 4
For acute urticaria, the American Academy of Allergy, Asthma, and Immunology recommends diphenhydramine 1-2 mg/kg every 4-6 hours, and considers combination with H2-antagonist for superior efficacy 1, 2, 3

Common adverse effects of diphenhydramine include sedation, dizziness, blurred vision, dry mouth, hypotension, and urinary retention, as reported by the American Academy of Pediatrics 3
Paradoxical excitation can occur, especially in younger children, as stated by the American Academy of Pediatrics 4
Drug interactions include enhanced sedation with alcohol, benzodiazepines, or opioid narcotics, and anticholinergic effects may worsen delirium from other anticholinergic drugs, as reported by the American Academy of Pediatrics 3, 4