Are steroids and antihistamines administered in cases of systemic anaphylaxis?

From the Guidelines

Yes, steroids and antihistamines are administered along with epinephrine in the treatment of systemic anaphylaxis. For immediate management, epinephrine (0.3-0.5 mg of 1:1000 solution intramuscularly in the mid-outer thigh for adults; 0.15 mg for children <30 kg) is the first-line treatment and should be given without delay 1.

Key Considerations

• H1 antihistamines such as diphenhydramine (25-50 mg IV/IM for adults; 1-2 mg/kg for children) help reduce urticaria and pruritus.
• H2 blockers like ranitidine (50 mg IV for adults; 1 mg/kg for children) may be added.
• Corticosteroids such as methylprednisolone (125 mg IV for adults; 1-2 mg/kg for children) or hydrocortisone (200 mg IV for adults) are given to prevent biphasic or protracted reactions, though they have a delayed onset of action (4-6 hours) 1.

Mechanism of Action

These medications work together to address different aspects of the allergic response:

• Epinephrine reverses vasodilation and increases cardiac output.
• Antihistamines block histamine-mediated symptoms.
• Steroids reduce inflammation and prevent prolonged or recurrent symptoms.

Monitoring and Follow-up

Patients should be monitored closely for at least 4-6 hours after symptom resolution due to the risk of biphasic reactions 1.

Limitations of Current Evidence

The certainty of evidence around supplemental therapies in anaphylaxis management is very low, and there is a need for randomized controlled trials to determine the effectiveness of glucocorticoids and antihistamines in preventing biphasic anaphylaxis 1.

From the FDA Drug Label

INDICATIONS AND USAGE: 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.

Treatment of systemic anaphylaxis may include the use of antihistamines such as diphenhydramine, as an adjunct to epinephrine and other standard measures, after the acute symptoms have been controlled.

• Steroids are not mentioned in the provided drug label as part of the treatment for systemic anaphylaxis.
• Antihistamines like diphenhydramine may be used in the treatment of systemic anaphylaxis, but only after the acute symptoms have been controlled 2.

From the Research

Treatment of Systemic Anaphylaxis

• The primary treatment for systemic anaphylaxis is intramuscular epinephrine, which is the first-line medication and should be administered promptly 3, 4, 5, 6, 7.
• After epinephrine administration, adjunct medications such as histamine H1 and H2 antagonists (antihistamines), corticosteroids, beta2 agonists, and glucagon may be considered 4, 6, 7.
• Antihistamines, such as histamine H1-antagonists, are valuable in mild anaphylactic reactions and can be given intravenously if possible 7.
• Glucocorticosteroids are given to prevent protracted or biphasic courses of anaphylaxis, but are of little help in the acute treatment 7.
• Steroids, such as glucocorticosteroids, are used as third-line treatment and their administration should never delay adrenaline injection in anaphylaxis 4.

Administration of Medications

• Epinephrine should be administered intramuscularly, and only in very severe cases or under conditions of surgical interventions can intravenous application be tried 7.
• Antihistamines and corticosteroids can be administered intravenously or orally, depending on the severity of the reaction and the patient's condition 4, 6, 7.
• The administration of these medications should be guided by the severity of the symptoms and the patient's response to treatment 4, 6, 7.

Important Considerations

• The treatment of systemic anaphylaxis should focus on removing the trigger, administering epinephrine, and providing supportive care for the patient's airway, breathing, and circulation 6.
• Patients should be monitored for a biphasic reaction, which can occur several hours after the initial reaction, and should be observed for a period of 4-12 hours depending on the risk factors for severe anaphylaxis 6.
• Educational programs for anaphylaxis have been developed to train patients 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 7.