Diphenhydramine Dosing for Pediatric Patients
For children under 6 years of age, diphenhydramine syrup should not be used according to FDA labeling. 1
Age-Based Dosing Recommendations
Children Under 6 Years
- Do not use diphenhydramine syrup in this age group per FDA labeling 1
- Safety concerns include potential toxicity and serious adverse events including fatalities reported in this age group 2
- The FDA's Nonprescription Drugs and Pediatric Advisory Committees recommended against using OTC cough and cold medications containing antihistamines in children under 6 years due to safety concerns 2
Children 6 to Under 12 Years
- Dose: 10 mL (25 mg) per dose 1
- Administer every 4-6 hours as needed
- Do not exceed 6 doses (150 mg) in 24 hours
- For anaphylaxis management (when used as adjunctive therapy): 1-2 mg/kg or 25 mg per dose parenterally 2
Children 12 Years and Older
- Dose: 10-20 mL (25-50 mg) per dose 1
- Administer every 4-6 hours as needed
- Do not exceed 6 doses (300 mg) in 24 hours
- For anaphylaxis management (when used as adjunctive therapy): 25-50 mg per dose 2, 3
Important Considerations
Safety Concerns
- Diphenhydramine and other first-generation antihistamines can cause significant sedation in over 50% of patients receiving therapeutic doses 4
- Between 1969 and 2006,69 fatalities were associated with antihistamines (including 33 with diphenhydramine) in children under 6 years 2
- Common causes of adverse events include:
- Use of multiple cold/cough products containing antihistamines
- Medication errors
- Accidental exposures
- Intentional overdose 2
Clinical Pearls
- Diphenhydramine is considered a second-line therapy for anaphylaxis and should never be administered alone in anaphylaxis treatment 2
- H1 antihistamines are only effective for cutaneous symptoms (urticaria, pruritus, flushing) and should not delay epinephrine administration in anaphylaxis 3
- The combination of H1 (diphenhydramine) and H2 (ranitidine) antagonists is superior to diphenhydramine alone for urticaria 2, 3
Monitoring
- Monitor for sedation, which may affect learning ability in children 4
- First-generation antihistamines like diphenhydramine can cause paradoxical behavioral disinhibition, especially in younger children and those with developmental disabilities 2
Alternative Options
- Second-generation antihistamines (cetirizine, desloratadine, fexofenadine, levocetirizine, and loratadine) have been shown to be well-tolerated with a better safety profile in young children 2, 5
- Consider these newer agents particularly for children under 6 years of age where diphenhydramine is not recommended 2
Remember that pediatric patients require individualized dosing based on age, size, and organ maturity—not simply reduced adult doses 6. When administering diphenhydramine to children, always follow the FDA-approved dosing guidelines and be vigilant for potential adverse effects.