Pediatric Diphenhydramine Dosing
The recommended dose of diphenhydramine (Benadryl) for pediatric patients is 1-2 mg/kg per dose, with a maximum single dose of 50 mg, administered every 4-6 hours as needed. 1
Age-Based Dosing Guidelines
- For children under 6 years of age: FDA labeling states "Do not use" for over-the-counter products 2, though in medical settings under physician supervision, the 1-2 mg/kg dosing is followed 1
- For children 6 to under 12 years of age: 10 mL (25 mg) per dose 2
- For children 12 years and older: 10-20 mL (25-50 mg) per dose 2
- Do not exceed 6 doses in 24 hours for any age group 2
Weight-Based Dosing Considerations
- For infants and young children under physician supervision, use the lower end of the dosing range (1 mg/kg) to minimize sedation risk 1
- For older children and adolescents, the full 1-2 mg/kg dose can be used, not exceeding the 50 mg maximum 1
- Children weighing less than 25 kg should receive carefully calculated doses based on the 1-2 mg/kg recommendation 1
Safety Thresholds
- Ingestions of 7.5 mg/kg or greater are considered potentially toxic in children under 6 years of age and should prompt medical evaluation 3, 4
- For children 6 years and older, ingestions of 7.5 mg/kg or 300 mg (whichever is less) are considered potentially toxic 3
- A validation study showed that 99.7% of children who ingested less than 7.5 mg/kg did not develop serious clinical effects 4
Administration Considerations
- Oral liquid formulations are more readily absorbed than tablets when used for acute allergic reactions 1
- When used for anaphylaxis management, diphenhydramine should always be considered second-line therapy to epinephrine 1
- For acute hypersensitivity reactions, the recommended dose remains 1-2 mg/kg or 25-50 mg per dose 1
Special Precautions
- Monitor for sedation, which is the most commonly reported adverse effect (observed in 95% of pediatric patients in one study) 5
- Paradoxical excitation or agitation may occur in some pediatric patients 1
- Avoid use with other sedative agents due to potential for respiratory suppression 1
- Pharmacokinetic studies show that after allometric scaling, diphenhydramine clearance increases with age but shows no maturation-related changes 5
Dosing Interval
Remember that pediatric patients are not simply "small adults" and require individualized dosing based on weight, age, and organ maturity to optimize efficacy and minimize adverse effects 6, 7.