Why is Pepcid (Famotidine) ordered during an allergic reaction?

From the Guidelines

Pepcid is ordered during allergic reactions because it acts as an H2 antihistamine, complementing H1 antihistamines like Benadryl to reduce symptoms of allergic reactions, as recommended in the management of milder, acute food-induced allergic reactions 1. When managing allergic reactions, the goal is to minimize morbidity, mortality, and improve quality of life by effectively controlling symptoms. According to the guidelines for the diagnosis and management of food allergy in the United States 1, milder forms of allergic reactions can be treated with H1 and H2 antihistamine medications. Key points to consider when using Pepcid in this context include:

• The medication works by blocking histamine receptors, specifically H2 receptors, which helps reduce stomach acid production and prevents blood vessel dilation contributing to allergic symptoms.
• The typical dose for adults is 20 mg orally or intravenously, while for children, it is weight-based at 0.25 mg/kg.
• Pepcid enhances the overall antihistamine effect when given together with H1 blockers, helping to reduce symptoms like hives, itching, and swelling more effectively 1.
• Ongoing observation and monitoring are warranted to ensure a lack of progression to more significant symptoms of anaphylaxis, and epinephrine should be administered immediately if progression or increased severity is noted 1.

From the Research

Allergic Reactions and Anaphylaxis

• Anaphylaxis is a rapid-onset, IgE-mediated hypersensitivity reaction that can cause airway, breathing, or circulatory compromise 2
• Symptoms of anaphylaxis can range from mild urticaria and swelling to respiratory collapse, and it is most commonly caused by food, insect stings, and medications 2

Treatment of Anaphylaxis

• Epinephrine is the first-line treatment for anaphylaxis, and it should be administered promptly once anaphylaxis is suspected 3
• Antihistamines and corticosteroids may also be used as adjunctive therapies, but the evidence for their use is limited 4
• Proton pump inhibitors (PPIs), such as Pepcid, are not typically used as a first-line treatment for anaphylaxis, but they may be used to treat gastrointestinal disorders that can occur concurrently with allergic reactions 5

Use of Pepcid in Allergic Reactions

• There is no direct evidence to support the use of Pepcid as a treatment for anaphylaxis or allergic reactions 2, 4, 3, 6
• However, PPIs like Pepcid may be used to treat gastrointestinal disorders that can occur concurrently with allergic reactions, such as gastroesophageal reflux disease 5