What is the recommended pediatric dosing for diphenhydramine (Benadryl)?

Pediatric Diphenhydramine Dosing

The recommended pediatric dose of diphenhydramine is 1-2 mg/kg per dose (maximum 50 mg per dose), administered every 4-6 hours as needed, but should NOT be used in children under 6 years of age for routine allergic symptoms due to significant safety concerns. 1, 2, 3

Standard Dosing by Age and Weight

Children 6 Years and Older

• Dose: 1-2 mg/kg per dose 1, 2
• Maximum single dose: 50 mg regardless of weight 1, 2, 3
• Frequency: Every 4-6 hours 3
• Maximum: 6 doses in 24 hours 3
• FDA-approved dosing: 10 mL (25 mg) for children 6 to under 12 years 3

Children Under 6 Years

• FDA labeling explicitly states "Do not use" for children under 6 years 3
• Critical safety warning: Between 1969-2006, diphenhydramine was responsible for 33 deaths in children under 6 years of age 4
• The American Academy of Pediatrics recommends avoiding OTC cough and cold medications (including first-generation antihistamines like diphenhydramine) in all children under 6 years due to lack of proven efficacy and potential toxicity 4

Clinical Context Considerations

For Acute Allergic Reactions/Anaphylaxis (Ages 6+ Only)

• Dose: 1-2 mg/kg or 25-50 mg per dose 2
• Route: Oral liquid formulations are more readily absorbed than tablets 1, 2
• Critical caveat: Diphenhydramine is second-line therapy only and should never replace epinephrine as first-line treatment 1, 2
• Combination with H2-antihistamine (ranitidine 1 mg/kg) is superior to diphenhydramine alone 2

Dosing Adjustments

• Infants and young children (if used under direct medical supervision): Use the lower end of the dosing range (1 mg/kg) 2
• Older children and adolescents: The full 1-2 mg/kg dose can be used, not exceeding 50 mg maximum 2
• Renal impairment: Reduce dose by 50% 2

Route-Specific Administration

Oral Administration

• Liquid formulations preferred over tablets for acute reactions due to faster absorption 1, 2
• Administer every 4-6 hours as needed 3

Intravenous Administration

• Same weight-based dosing: 1-2 mg/kg per dose, maximum 50 mg 1
• Must administer slowly to prevent seizures 2
• Monitor for sedation and respiratory suppression, especially with concurrent sedative agents 2

Safety Warnings and Monitoring

Common Adverse Effects

• Sedation is expected in 95% of patients 5
• Paradoxical excitation or agitation may occur in some pediatric patients 2
• Monitor for respiratory depression, particularly with rapid IV administration or concurrent sedatives 2

Toxicity Thresholds

• Children under 6 years: Ingestions ≥7.5 mg/kg warrant emergency department referral 6
• Children 6 years and older: Ingestions ≥7.5 mg/kg or ≥300 mg (whichever is less) warrant emergency department referral 6

Preferred Alternatives for Routine Allergic Symptoms

For children under 6 years with routine allergic symptoms, second-generation antihistamines are strongly preferred: 4

• Cetirizine: 2.5 mg once or twice daily for ages 2-5 years 4
• Loratadine: 5 mg once daily for ages 2-5 years 4
• These agents have superior safety profiles with significantly lower rates of serious adverse events and fewer sedating effects 4

Key Clinical Pitfalls to Avoid

• Never use diphenhydramine "to make a child sleepy" - this is explicitly contraindicated per FDA labeling 4
• Never use for anticholinergic delirium - may worsen symptoms 2
• Never use as monotherapy for anaphylaxis - epinephrine is always first-line 1, 2
• Avoid topical formulations in young children - fatal toxicity has been reported from topical application 7
• Do not administer activated charcoal at home due to risk of loss of consciousness or seizures 6