What is the appropriate dosage of Diphenhydramine (Benadryl) and Famotidine (Pepcid) for an allergic reaction in a 1-year-old child weighing 14.6 kilograms?

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Last updated: April 26, 2025View editorial policy

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From the Guidelines

For a 1-year-old child weighing 14.6kg with an allergic reaction, I recommend diphenhydramine (Benadryl) at 1-2mg/kg/dose, which would be 14.6-29.2mg, and considering the available formulations, a dose of 15mg every 6 hours as needed can be given as children's liquid Benadryl (12.5mg/5mL), so approximately 6mL per dose, as suggested by 1. For famotidine (Pepcid), the recommended dose is 1mg/kg, which would be approximately 14.6mg, as indicated by 1. These medications work together to block different histamine receptors - Benadryl blocks H1 receptors causing the immediate allergic symptoms like hives and itching, while Pepcid blocks H2 receptors which can help reduce some inflammatory responses. Some key points to consider:

  • The combination of diphenhydramine and ranitidine is superior to diphenhydramine alone in the management of anaphylaxis, as noted by 1.
  • For mild allergic reactions, these medications may be sufficient, but it is crucial to monitor the child closely for any signs of respiratory distress, facial swelling, or vomiting, as emphasized by 1.
  • If these occur or if symptoms worsen, seek immediate medical attention as this could indicate anaphylaxis requiring emergency treatment, such as epinephrine administration, as highlighted by 1 and 1.
  • Always consult with a healthcare provider before administering these medications, especially in young children, to ensure the best possible outcome in terms of morbidity, mortality, and quality of life.

From the Research

Allergic Reaction Management

  • The management of allergic reactions, including anaphylaxis, is crucial for preventing severe outcomes 2, 3, 4.
  • Epinephrine is universally recommended as the first-line therapy for anaphylaxis, and early treatment is critical to prevent a potentially fatal outcome 3, 4, 5.

Treatment Options

  • Antihistamines, such as Benadryl, may be used as adjunctive therapy, but they do not relieve or prevent all of the pathophysiological symptoms of anaphylaxis 3, 5.
  • Corticosteroids, such as Pepcid, may be used in some cases, but the evidence for their use in anaphylaxis management is limited 5.

Specific Considerations for a 1-year-old, 14.6kg Child

  • The use of epinephrine, antihistamines, and corticosteroids in pediatric patients requires careful consideration of the child's weight and age 5.
  • The American Academy of Pediatrics recommends developmental surveillance and screening for various health issues during well-child visits, but does not provide specific guidance on the use of Benadryl and Pepcid for allergic reactions in infants 6.

Evidence Limitations

  • There is limited evidence on the use of Benadryl and Pepcid for allergic reactions in infants, and more research is needed to determine the safety and efficacy of these medications in this population 2, 3, 4, 5.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Managing anaphylaxis: Epinephrine, antihistamines, and corticosteroids: More than 10 years of Cross-Canada Anaphylaxis REgistry data.

Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology, 2023

Research

Well-Child Visits for Infants and Young Children.

American family physician, 2018

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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