What are the initial intravenous (IV) medications to administer for an allergic reaction?

From the Guidelines

The initial intravenous medication for treating an allergic reaction should be epinephrine (adrenaline) as the first-line treatment, typically given at 0.3-0.5 mg (1:1000 concentration) for adults or 0.01 mg/kg for children, as it is the most effective medication for rapidly reversing the symptoms of anaphylaxis 1. The use of epinephrine is supported by the most recent and highest quality studies, which emphasize its importance in the acute management of anaphylaxis 1. Some key points to consider when administering epinephrine include:

• The dose and concentration of epinephrine, which is typically 0.3-0.5 mg (1:1000 concentration) for adults or 0.01 mg/kg for children 1
• The route of administration, which is typically intramuscularly in the anterolateral thigh, but can be given intravenously in certain situations 1
• The importance of administering epinephrine promptly, as delayed administration can be associated with poor outcomes, including fatality 1 In addition to epinephrine, other medications such as antihistamines and corticosteroids may be used as adjunctive therapy, but they should not be administered prior to, or in place of, epinephrine 1. Some key points to consider when using these medications include:
• Antihistamines, such as diphenhydramine (Benadryl), can help block histamine effects, but they work more slowly than epinephrine and are not effective in treating acute symptoms such as hypotension or bronchospasm 1
• Corticosteroids, such as methylprednisolone, may help prevent biphasic or prolonged reactions by reducing inflammation, but their effects take hours to manifest and they have a limited role in the acute management of anaphylaxis 1 It is also important to note that the use of these medications should be guided by the patient's response and the severity of their symptoms, and that continuous monitoring of vital signs is essential 1. In cases of bronchospasm, albuterol nebulization may be added, and IV fluids (normal saline) should be administered to maintain blood pressure if hypotension is present 1. Overall, the key to effectively managing an allergic reaction is to administer epinephrine promptly and to use adjunctive medications, such as antihistamines and corticosteroids, as needed to support the patient's care.

From the Research

Initial IV Medications for Allergic Reactions

The following are the initial intravenous (IV) medications to administer for an allergic reaction:

• Epinephrine is the first-line treatment for anaphylaxis, an acute potentially life-threatening allergic reaction 2, 3, 4
• The initial recommended adult dose is 0.3-0.5 mg, injected intramuscularly in the anterolateral aspect of the mid-thigh 4
• For severe anaphylaxis, multiple epinephrine doses may be required, and a "1-2-3" approach to anaphylaxis treatment is recommended 5
• Glucocorticosteroids are given to prevent protracted or biphasic courses of anaphylaxis, and histamine H(1)-antagonists are valuable in mild anaphylactic reactions 3
• Replacement of volume is crucial in antianaphylactic treatment, and crystalloids or colloid volume substitutes can be used 3

Administration Routes and Doses

• Epinephrine is most effective when given immediately after the onset of anaphylaxis symptoms, and it is typically administered intramuscularly 2, 4
• Intravenous application of epinephrine can be tried in very severe cases or under conditions of surgical interventions 3
• The dose of epinephrine can vary depending on the patient's weight, and the Canadian Society of Allergy and Immunology (CSACI) recommends prescribing the 0.50 mg EAI for patients who weigh ≥ 45 kg 2

Additional Considerations

• Patients suffering from an anaphylactic episode should be observed over a period of 4-10 h according to the severity of the symptomatology 3
• It is crucial to be aware of risk patients, such as those with severe uncontrolled asthma, or under beta-adrenergic blockade 3
• 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 3