What is the recommended dose of Diphenhydramine (Benadryl) per kilogram of body weight for pediatric patients, according to the FDA drug label, considering age and safety?

Diphenhydramine Dosing for Pediatric Patients: FDA Guidelines and Safety

For pediatric patients, diphenhydramine (Benadryl) should be dosed at 1-2 mg/kg/dose with a maximum of 50 mg per dose for children, according to clinical practice guidelines. 1

Age-Based Dosing Recommendations

• For children under 6 years of age:

  • 1-2 mg/kg/dose parenterally (IV/IM) 1
  • Maximum single dose should not exceed 50 mg 1
  • Typically administered every 6-8 hours as needed 1

• For children 6-12 years:

  • 12.5-25 mg per dose (oral or parenteral) 1
  • Maximum daily dose should not exceed 150 mg 2

• For adolescents (>12 years):

  • 25-50 mg per dose 1
  • Maximum single dose of 50 mg 1

Safety Considerations

• Toxic threshold: Children less than 6 years of age who ingest at least 7.5 mg/kg of diphenhydramine should be referred to an emergency department 2

• Formulation considerations:

  • Liquid formulations are most commonly involved in pediatric exposures (51.7%) 3
  • Syrup formulations facilitate administration to children 4

• Common adverse effects in pediatric patients:

  • Tachycardia (53.4% of adverse events) 3
  • Hallucinations (46.5%) 3
  • Somnolence/sedation (34.7%) 3
  • Agitation (33.9%) 3
  • Mydriasis (26.3%) 3

Special Populations and Precautions

• Children weighing more than 40 kg should be dosed as adults 1

• Dose reduction is recommended in:

  • Renal impairment: reduce dose by 50% 4
  • Avoid in severe renal impairment (creatinine clearance <10 mL/min) 4
  • Avoid in severe hepatic impairment 4

• Most adverse events occur in children 2 to <4 years of age (79.5% of cases) 3

• Accidental unsupervised ingestions account for 74.7% of pediatric diphenhydramine exposures 3

Clinical Pearls

• Second-generation antihistamines are preferred over diphenhydramine in children due to better safety profile 5

• Diphenhydramine should be considered second-line therapy to epinephrine in anaphylaxis and should never be administered alone for this indication 1

• When used for chemical restraint in agitated pediatric patients, diphenhydramine is often combined with antipsychotics (typical or atypical) 1

• Pharmacokinetic studies show that after allometric scaling, there is no maturation-related change in clearance across pediatric age groups 6

• Monitoring for cognitive effects is particularly important, as diphenhydramine is associated with increased risk of cognitive decline with a dose-response relationship 7