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

Pediatric Diphenhydramine (Benadryl) Dosing Guidelines

The recommended diphenhydramine (Benadryl) dosing for pediatric patients is 1-2 mg/kg/dose with a maximum of 50 mg per dose, administered every 4-6 hours as needed, with children under 6 years of age requiring physician guidance before administration. 1, 2

Age-Based Dosing Recommendations

Children under 6 years:

• Not recommended for over-the-counter use 2
• Physician guidance required for this age group
• When prescribed by a physician: 1-2 mg/kg/dose 1

Children 6 to under 12 years:

• 10 mL (25 mg) per dose 2
• Do not exceed 6 doses in 24 hours 2
• Interval: Every 4-6 hours 2

Children 12 years and older and adults:

• 10-20 mL (25-50 mg) per dose 2
• Do not exceed 6 doses in 24 hours 2
• Interval: Every 4-6 hours 2

Weight-Based Dosing for Parenteral Administration

For situations requiring parenteral administration (such as in anaphylaxis management):

• Diphenhydramine: 1-2 mg/kg per dose 1
• Maximum dose: 50 mg 1
• Route: IV or oral (oral liquid is more readily absorbed than tablets) 1

Safety Considerations

Toxicity Thresholds

• Children <6 years: Refer to emergency department if ingestion ≥7.5 mg/kg 3
• Children ≥6 years: Refer to emergency department if ingestion ≥7.5 mg/kg or ≥300 mg (whichever is less) 3

Common Adverse Effects

• Mild drowsiness is the most commonly reported adverse event (95% of pediatric subjects in pharmacokinetic studies) 4
• More serious adverse events with overdose include tachycardia, hallucinations, somnolence, agitation, and mydriasis 5

Important Clinical Pearls

1. Formulation matters: Liquid formulations are more readily absorbed than tablets and are preferred for children 1

2. Pharmacokinetics: Peak concentration (Tmax) occurs at approximately 1.5 hours after oral administration in children 4

3. Monitoring: After administration, monitor for excessive sedation, particularly in younger children 5

4. Accidental ingestion risk: Most adverse events in children under 4 years are from accidental unsupervised ingestions (74.7%) 5

5. Calculation errors: Weight-based dosing requires careful calculation to avoid medication errors, especially in emergency settings 6

Special Situations

Anaphylaxis Management

When used as adjunctive treatment in anaphylaxis:

• Diphenhydramine 1-2 mg/kg per dose (maximum 50 mg) 1
• Note: H1 antihistamines are considered second-line therapy to epinephrine and should never be administered alone in the treatment of anaphylaxis 1

Dosing in Emergency Settings

• In emergency situations, a combination of diphenhydramine and ranitidine is superior to diphenhydramine alone for anaphylaxis management 1
• Careful weight-based dosing calculations are essential to avoid medication errors 6

Remember that diphenhydramine is not a first-line treatment for anaphylaxis, and epinephrine should always be administered first in such cases 1.