What is the treatment for an anaphylactoid (anaphylactic-like) reaction?

From the Guidelines

The immediate treatment of an anaphylactoid reaction involves administering epinephrine (adrenaline) as the first-line therapy, typically given as 0.3-0.5 mg (0.3-0.5 mL of 1:1000 solution) intramuscularly in the mid-outer thigh for adults, or 0.15 mg for children weighing less than 30 kg, as recommended by the most recent and highest quality study 1. This can be repeated every 5-15 minutes if symptoms persist. Simultaneously, ensure the patient's airway is secure, provide supplemental oxygen, and establish intravenous access for fluid resuscitation with normal saline to combat hypotension. Second-line medications include antihistamines such as diphenhydramine (25-50 mg IV/IM for adults) to block histamine effects, and corticosteroids like methylprednisolone (125 mg IV) or hydrocortisone (200 mg IV) to prevent biphasic or prolonged reactions, although their role is limited in the acute management of anaphylaxis 1. For bronchospasm, consider albuterol via nebulizer. Patients should be placed in a supine position with legs elevated unless respiratory distress prevents this. Continuous monitoring of vital signs is essential. Epinephrine works rapidly by causing vasoconstriction, reducing mucosal edema, increasing cardiac output, and bronchodilation, directly counteracting the life-threatening effects of the anaphylactoid reaction, as supported by previous studies 1. After stabilization, patients should be observed for at least 4-6 hours due to the risk of biphasic reactions, and those with severe reactions may require admission for monitoring. Key points to consider in the treatment of anaphylactoid reactions include:

• The importance of prompt administration of epinephrine, as delayed use can be ineffective and even fatal 1
• The role of antihistamines and glucocorticoids as adjunctive therapy, but not as substitutes for epinephrine 1
• The need for continuous monitoring of vital signs and observation for at least 4-6 hours after stabilization 1

From the FDA Drug Label

The FDA drug label does not answer the question.

From the Research

Treatment of Anaphylactoid Reaction

• The treatment of anaphylactoid reactions involves removal of the trigger, early administration of intramuscular epinephrine, and supportive care for the patient's airway, breathing, and circulation 2.
• Adjunct medications such as histamine H1 and H2 antagonists, corticosteroids, beta2 agonists, and glucagon may be considered after epinephrine administration 2, 3.
• Patients should be monitored for a biphasic reaction, which is a recurrence of anaphylaxis without reexposure to the allergen, for four to 12 hours, depending on risk factors for severe anaphylaxis 2, 3.

Acute Management

• The acute management of anaphylaxis involves general procedures such as positioning, applying an intravenous catheter, calling for help, and comforting the patient, as well as the application of medication 3.
• Epinephrine is the essential antianaphylactic drug in the pharmacologic treatment and should be applied intramuscularly, with intravenous application only in very severe cases or under conditions of surgical interventions 3, 4.
• Glucocorticosteroids are given to prevent protracted or biphasic courses of anaphylaxis, but are of little help in the acute treatment 3.

Prevention and Education

• Patients who have survived an anaphylactic reaction should be thoroughly examined and an allergy diagnosis should be performed with regard to the eliciting agent and the pathogenic mechanism involved 3.
• Patients should be trained on the nature of anaphylaxis, the major eliciting agents, and the principles of behavior and coping with the situation, including the handling of epinephrine autoinjectors and the application of antianaphylactic medication 3, 5.
• Educational programs for anaphylaxis have been developed to help patients and physicians manage these reactions effectively 3.

Medication Use

• Epinephrine is the first-line treatment for anaphylaxis, and delayed epinephrine administration is a risk factor for fatal anaphylaxis 6.
• Antihistamines may be beneficial in the treatment of anaphylaxis, but convincing data on their role are sparse 6.
• Corticosteroid use in anaphylaxis should be revisited, as it may be associated with an increased risk of requiring intravenous fluids and hospital admission 6.