What is the treatment for a patient with a severe allergic reaction, potentially with a history of severe allergic reactions, presenting to urgent care?

Urgent Care Treatment of Severe Allergic Reactions

Intramuscular epinephrine is the first-line, life-saving treatment for anaphylaxis and must be administered immediately without delay—all other medications are secondary and should never delay epinephrine administration. 1, 2, 3

Immediate Recognition and Treatment

Primary Treatment: Epinephrine

• Administer epinephrine 0.3-0.5 mg (0.3-0.5 mL of 1:1,000 solution) intramuscularly into the anterolateral thigh for adults and children ≥30 kg 3
• For children <30 kg, give 0.01 mg/kg (maximum 0.3 mg) intramuscularly into the anterolateral thigh 1, 2, 3
• Repeat doses every 5-15 minutes as needed if symptoms persist or progress—approximately 7-18% of patients require more than one dose 1, 2, 3
• The intramuscular route in the lateral thigh achieves peak concentrations rapidly and is safer than intravenous bolus injection 1

Simultaneous Actions

• Activate emergency medical services (call 911) immediately 1, 2
• Position patient supine with legs elevated (or in position of comfort if respiratory distress) 1, 2
• Administer supplemental oxygen for any respiratory distress 2

Adjunctive Medications (Second-Line)

These medications provide symptomatic relief but do NOT replace epinephrine and should be given simultaneously with or immediately after epinephrine:

H1 Antihistamines

• Diphenhydramine 1-2 mg/kg (maximum 50 mg) IV or orally for urticaria and pruritus 1, 4, 2
• This provides symptomatic relief but does not reverse life-threatening cardiovascular or respiratory manifestations 2

H2 Antihistamines

• Ranitidine 50 mg IV (adults) or 1 mg/kg (children, maximum 50 mg) administered over 5 minutes 1, 4
• The combination of H1 and H2 antihistamines is superior to H1 alone for preventing severe cardiac deficits 2

Bronchodilators

• Albuterol 4-8 puffs (children) or 8 puffs (adults) via MDI, or 1.5 mL (children) or 3 mL (adults) via nebulizer for wheezing or bronchospasm resistant to epinephrine 1, 2

IV Fluids

• Large volume boluses of 10-20 mL/kg, repeated as needed for orthostasis, hypotension, or incomplete response to epinephrine 2

Refractory Cases

For Hypotension Unresponsive to Epinephrine and Fluids

• Consider continuous IV epinephrine infusion with continuous non-invasive blood pressure and heart rate monitoring 1, 2
• Dopamine infusion (400 mg in 500 mL of 5% dextrose) at 2-20 mg/kg/min can be titrated to maintain systolic blood pressure >90 mm Hg 1

Special Consideration: Beta-Blocker Patients

• Patients on beta-blockers may have reduced response to epinephrine and should receive glucagon 1-2 mg IV as epinephrine may be less effective in this population 4, 2

Observation Period

All patients who receive epinephrine must be observed for a minimum of 4-6 hours 4, 2

Extended Observation (12 hours) Required For:

• Severe initial reactions 2
• History of biphasic reactions 2
• Delayed epinephrine administration 2
• Ongoing symptoms despite treatment 2

Discharge Planning

Prescriptions at Discharge

• Two epinephrine autoinjectors with hands-on training 1, 2
• 2-3 day course of diphenhydramine (every 6 hours), H2 antihistamine (ranitidine twice daily), and prednisone to prevent biphasic reactions 4, 2

Documentation and Follow-Up

• Written anaphylaxis emergency action plan listing triggers, symptoms, and treatment steps 1, 2
• Medical identification jewelry or wallet card 1, 2
• Follow-up appointments with primary care physician and allergist/immunologist 2

Critical Pitfalls to Avoid

• Never delay epinephrine for antihistamines or bronchodilators—epinephrine is the only medication that reverses life-threatening manifestations 1, 5
• Never inject epinephrine into buttocks, digits, hands, or feet due to risk of tissue injury 3
• Do not rely on antihistamines alone for multi-system involvement—this represents anaphylaxis requiring epinephrine 4, 2
• Pregnant patients should receive epinephrine without hesitation—maternal hypoxia poses greater fetal risk than epinephrine 4
• Patients with cardiovascular disease still require epinephrine—serious adverse effects are rare in otherwise healthy individuals, and the benefits outweigh risks 2