New federal guidelines on food allergy recommend "prompt and rapid" treatment of food-induced anaphylaxis with intramuscular epinephrine as first-line therapy.
And in cases of a suboptimal response to epinephrine – or if symptoms progress – "repeat epinephrine dosing remains first-line therapy over adjunctive treatments," the guidelines say.
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Intramuscular epinephrine should be first-line therapy for anaphylaxis caused by food allergy, according to new federal guidelines.
The "consistency and strength" of the recommendation for prompt treatment with IM epinephrine may come as a surprise to some emergency physicians who "reserve treatment with epinephrine until patients are in shock, which is an extreme and late manifestation" of anaphylaxis, said Dr. Carlos A. Camargo Jr., an emergency physician who served on the multidisciplinary expert panel that developed the guidelines for the National Institute of Allergy and Infectious Diseases.
"Earlier diagnosis of anaphylaxis and earlier treatment with epinephrine would benefit patients," said Dr. Camargo of Massachusetts General Hospital and Harvard Medical School, both in Boston. "The guidelines strongly encourage earlier use of IM epinephrine for food-induced anaphylaxis."
Studies suggest that almost half of food-related allergic reactions in the emergency department involve multiple organ systems and therefore qualify as anaphylaxis, he said in an interview.
The guidelines, published in the December issue of the Journal of Allergy and Clinical Immunology, were based on a systematic literature review combined with consensus expert opinion, and were designed to standardize the diagnosis and management of food allergies across clinical settings and disciplines (J. Allergy Clin. Immunol. 2010;126:1105-18).
Expert opinion played a prominent role in the development of the guidelines – particularly in the section on managing acute allergic reactions to food – because there have been few, if any, controlled studies on food-induced anaphylaxis management, the 25-member expert panel said in the report.
Anaphylaxis, whether food induced or not, is significantly underrecognized and undertreated, they wrote. One possible reason, the panel said, is the "failure to appreciate that anaphylaxis can present without obvious cutaneous symptoms, which happens in 10%-20% of cases, or without overt shock."
Food-induced anaphylaxis can occur within minutes to several hours after a defined exposure to a food allergen. Although it can sometimes take a milder course and resolve spontaneously, it can also be fatal. Deaths from food-induced anaphylaxis have been reported within 30 minutes to 2 hours of exposure, and are associated with delayed use of epinephrine or improper epinephrine dosing, the panel said.
The guidelines, which include guidance and dosing information for epinephrine and various adjunctive treatments – from inhaled bronchodilators and antihistamines to vasopressors and glucagons – caution specifically against the use of H1 and H2 antihistamines for anaphylaxis in anything but an adjunctive role.
Antihistamines such as diphenhydramine are commonly used to treat anaphylaxis, but the report noted that data demonstrating their effectiveness are lacking. Similarly, "there is no persuasive evidence for the use of corticosteroids in acute food-related allergic reactions," Dr. Camargo said.
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Epinephrine has an onset of action within minutes but is rapidly metabolized. Repeated doses of epinephrine may therefore be required after 5-15 minutes, the guidelines say. Among individuals who require epinephrine for anaphylaxis, approximately 10%-20% will require more than one dose, Dr. Camargo emphasized.
The expert panel acknowledged in its report that some level of decision making regarding the risk-benefit ratio of epinephrine "may be warranted" for some patients, but it emphasized that severe adverse effects are rare with epinephrine and are more likely to occur when the drug is given in overdose than in other circumstances.
"Because the risk of death or serious disability from anaphylaxis itself usually outweighs other concerns, existing evidence clearly favors the benefit of epinephrine administration in most situations," the guidelines state.
IM injection of epinephrine should be quickly followed by placement of the patient in a recumbent position (if tolerated, and with lower extremities elevated), the provision of supplemental oxygen, and the administration of intravenous fluid, the panel noted.
Not enough is known, the panel noted, about the true incidence of biphasic and protracted reactions related to food-induced anaphylaxis and how to best prevent or treat these reactions.
Another "knowledge gap" concerns the relative benefits of certain alternative routes of epinephrine administration, such as sublingual administration.
And although little is known about the most effective methods for educating and protecting patients at risk for food-induced anaphylaxis, the guidelines recommend a thorough discharge plan following treatment for food-induced anaphylaxis – one that includes a plan for arranging further evaluation, an anaphylaxis emergency action plan, and an epinephrine auto-injector (two doses) with instructions and a plan for monitoring auto-injector expiration dates.