What is the first‑line management of anaphylaxis caused by pufferfish exposure?

First-Line Management of Pufferfish-Induced Anaphylaxis

Administer intramuscular epinephrine 0.01 mg/kg (maximum 0.5 mg for adults, 0.3 mg for children) into the mid-outer thigh immediately upon recognizing anaphylaxis from pufferfish exposure—this is the only first-line treatment that prevents death. 1

Immediate Actions (First 60 Seconds)

• Stop any ongoing pufferfish ingestion and remove the patient from the source. 2
• Inject epinephrine intramuscularly into the vastus lateralis (mid-outer thigh) using 1:1000 concentration (1 mg/mL): 0.3–0.5 mg for adults/adolescents >50 kg, or 0.01 mg/kg (maximum 0.3 mg) for prepubertal children. 1, 3
• Call emergency medical services (911/EMS) immediately while treating—do not delay epinephrine to wait for help. 1
• Position the patient supine with legs elevated unless respiratory distress or vomiting requires a more comfortable position; never allow the patient to stand or walk, as postural changes can precipitate cardiovascular collapse. 1, 3

The anterolateral thigh injection site is critical because it achieves peak plasma epinephrine concentrations in 8±2 minutes, compared to 34±14 minutes with subcutaneous administration. 3 There are no absolute contraindications to epinephrine in anaphylaxis, even in elderly patients with cardiovascular disease—the risk of death from untreated anaphylaxis far outweighs any epinephrine-related risk. 2, 3

Repeat Dosing Protocol

• Repeat intramuscular epinephrine every 5–15 minutes if symptoms persist, worsen, or recur; approximately 10–20% of patients require more than one dose. 1, 3
• Fish (including pufferfish) is specifically identified as a trigger associated with severe and fatal anaphylaxis, making aggressive repeat dosing particularly important. 2

Adjunctive Treatments (Only AFTER Epinephrine)

Oxygen and Fluid Resuscitation

• Administer supplemental oxygen at 6–8 L/min for any respiratory symptoms. 1, 3
• Establish IV access and infuse normal saline rapidly: 5–10 mL/kg in the first 5 minutes for adults (1–2 L total), or up to 30 mL/kg in the first hour for children, to counteract vasodilation and capillary leak. 1, 3

Second-Line Medications (Never Substitutes for Epinephrine)

• H1 antihistamine (diphenhydramine): 25–50 mg IV/IM for adults (1–2 mg/kg for children) addresses only cutaneous symptoms (urticaria, itching) and does not relieve airway obstruction, bronchospasm, or shock. 1, 3
• Albuterol nebulizer (2.5–5 mg in 3 mL saline) may be used for persistent bronchospasm after epinephrine but does not treat airway edema. 3
• Corticosteroids are NOT recommended for acute anaphylaxis—they have a 4–6 hour onset and no proven benefit in preventing biphasic reactions or improving acute outcomes. 3

Observation and Transfer Requirements

• All patients must be transferred to an emergency department by EMS for observation, regardless of symptom improvement. 1
• Minimum observation period is 4–6 hours after complete symptom resolution; patients requiring multiple epinephrine doses need extended observation (up to 6 hours or admission) due to 1–20% risk of biphasic reactions occurring up to 72 hours later. 1, 3

Discharge Planning

• Prescribe two epinephrine autoinjectors (0.15 mg for 10–25 kg; 0.3 mg for ≥25 kg) with hands-on training before discharge. 1, 3
• Provide a written anaphylaxis emergency action plan detailing symptoms, triggers (pufferfish/fish), and epinephrine use instructions. 1, 3
• Refer to an allergist for evaluation within 1–2 weeks to identify cross-reactive fish allergens and assess ongoing risk. 1

Critical Pitfalls to Avoid

• Never delay epinephrine while establishing IV access or administering antihistamines—delayed epinephrine is directly associated with anaphylaxis fatalities. 2, 3
• Do not rely on antihistamines or corticosteroids as primary treatment—they address only minor symptoms and do not prevent cardiovascular collapse or airway obstruction. 2, 1
• Do not use subcutaneous epinephrine—intramuscular injection in the thigh is mandatory for optimal absorption. 3
• Do not discharge patients after brief observation—fish-triggered anaphylaxis carries high risk of severe reactions and biphasic recurrence. 2, 3