From the Guidelines
Epinephrine is the primary medication used to treat severe allergic reactions, including anaphylaxis, and should be administered promptly via an auto-injector, such as an EpiPen, followed by emergency medical attention. For mild to moderate allergic reactions, antihistamines like diphenhydramine (Benadryl) 25-50mg every 4-6 hours or cetirizine (Zyrtec) 10mg daily can provide relief, while H2 blockers such as famotidine (Pepcid) 20mg twice daily may also be helpful for reactions with hives or itching 1. It is essential to note that antihistamines and other medications should not replace epinephrine in the treatment of anaphylaxis, but rather serve as adjunctive therapy 1. The recommended dose of epinephrine is 0.3 mg intramuscularly for adults and children greater than 30 kg, and 0.15 mg intramuscularly for children 15 to 30 kg, or as prescribed by a physician 1. After any significant reaction, it is crucial to avoid the triggering medication completely, ensure it is documented in medical records, and consider wearing a medical alert bracelet listing medication allergies 1.
Some key points to consider when treating allergic reactions include:
- Epinephrine is the first-line treatment for anaphylaxis and should be administered promptly
- Antihistamines and H2 blockers can provide relief for mild to moderate reactions
- Corticosteroids may be used as adjunctive therapy to prevent late-onset activation of immune mediators
- It is essential to avoid the triggering medication and ensure proper documentation and medical alert measures are in place
- Always inform healthcare providers about medication allergies to prevent accidental re-exposure 1.
In terms of specific medications and dosages, the following may be considered:
- Diphenhydramine (Benadryl) 25-50mg every 4-6 hours
- Cetirizine (Zyrtec) 10mg daily
- Famotidine (Pepcid) 20mg twice daily
- Epinephrine auto-injector (EpiPen 0.3mg or EpiPen Jr 0.15mg for children) injected into the outer thigh
- Corticosteroids, such as prednisone, may be prescribed for adjunctive therapy 1.
It is essential to prioritize the most recent and highest quality study, which in this case is 1, to ensure the best possible outcomes in terms of morbidity, mortality, and quality of life.
From the FDA Drug Label
Adrenalin® is a non-selective alpha and beta adrenergic agonist indicated for: Emergency treatment of allergic reactions (Type 1), including anaphylaxis Diphenhydramine hydrochloride in the injectable form is effective in adults and pediatric patients, other than premature infants and neonates, for the following conditions when diphenhydramine hydrochloride in the oral form is impractical Antihistaminic For amelioration of allergic reactions to blood or plasma, in anaphylaxis as an adjunct to epinephrine and other standard measures after the acute symptoms have been controlled, and for other uncomplicated allergic conditions of the immediate type when oral therapy is impossible or contraindicated. Adrenalin® is available as a single-use 1 mL vial and a multiple-use 30 mL vial for intramuscular and subcutaneous use. Emergency treatment of allergic reactions (Type I), including anaphylaxis, which may result from allergic reactions to insect stings, biting insects, foods, drugs, sera, diagnostic testing substances and other allergens, as well as idiopathic anaphylaxis or exercise-induced anaphylaxis.
The medications used to treat allergic reactions are:
- Epinephrine (IM), used for emergency treatment of allergic reactions (Type 1), including anaphylaxis 2, 2
- Diphenhydramine (IV), used as an adjunct to epinephrine and other standard measures after the acute symptoms have been controlled, for amelioration of allergic reactions to blood or plasma, in anaphylaxis 3
From the Research
Medications for Allergic Reactions
- Epinephrine is the essential antianaphylactic drug in the pharmacologic treatment of anaphylaxis, and it should be applied intramuscularly 4
- Glucocorticosteroids are given to prevent protracted or biphasic courses of anaphylaxis, but they are of little help in the acute treatment 4
- Histamine H(1)-antagonists are valuable in mild anaphylactic reactions and should be given intravenously if possible 4
- Antihistamines are most commonly used in the treatment of allergies, but not all drugs are equally effective and safe for the patient 5
- Diphenhydramine can be used to treat allergic reactions, but it can also cause acute dystonic reactions in some patients 6
Treatment of Hypersensitivity Reactions to Corticosteroids
- Prick and intradermal skin tests are useful diagnostic tools for immediate hypersensitivity reactions to corticosteroids 7, 8
- Patch tests are useful for delayed hypersensitivity reactions to corticosteroids 7, 8
- An alternative (safe) corticosteroid agent should be administered based on the diagnostic tests 7
- Cross-reactivity patterns have not been observed for immediate hypersensitivity reactions, but they have been observed for delayed contact dermatitis based on corticosteroid structure 8