What is the recommended intramuscular (IM) steroid and dosage for a 13-year-old female patient with a severe allergic reaction?

IM Steroid for Severe Allergic Reaction in a 13-Year-Old Female

For a 13-year-old female with severe allergic reaction (anaphylaxis), administer methylprednisolone 1 mg/kg IM (maximum 60-80 mg) as adjunctive therapy AFTER epinephrine has been given first. 1, 2

Critical First-Line Treatment

• Epinephrine 0.01 mg/kg IM (0.3 mg for patients ≥25 kg or 0.15 mg for 10-25 kg) into the anterolateral thigh is the ONLY first-line treatment and must be given immediately—never delay this for steroids. 2, 3
• Repeat epinephrine every 5-15 minutes if symptoms persist or progress. 2, 3

IM Steroid Dosing Options

Methylprednisolone is the preferred IM steroid:

• Dose: 1-2 mg/kg IM (maximum 60-80 mg) 1, 2, 4
• For a typical 13-year-old female (approximately 40-50 kg), this translates to 40-60 mg IM 1

Alternative: Dexamethasone (if methylprednisolone unavailable):

• Dose: 1-2 mg/kg IM 3, 5
• For airway obstruction specifically, higher doses of dexamethasone (1.0-1.5 mg/kg) may be used 5

Role and Limitations of Steroids

• Corticosteroids provide NO acute benefit in anaphylaxis—they only potentially prevent biphasic reactions (which occur in up to 20% of cases) and protracted anaphylaxis occurring 4-12 hours later. 2, 3
• Steroids should be considered particularly for patients with: 2
  • History of asthma
  • Severe or prolonged anaphylaxis requiring multiple epinephrine doses
  • Significant respiratory involvement

Complete Management Algorithm

After epinephrine administration:

1. Position patient supine with legs elevated (unless respiratory distress/vomiting present) 2
2. Administer methylprednisolone 1 mg/kg IM (maximum 60-80 mg) 1, 2
3. Add H1-antihistamine: Diphenhydramine 1-2 mg/kg IM/IV (maximum 50 mg) 1, 2, 4
4. Add H2-antihistamine: Ranitidine 1 mg/kg (maximum 75-150 mg) 1
5. Observe for minimum 6 hours after symptom resolution 2, 3

Discharge Protocol

Every patient must receive: 2, 4

• Prednisone 1 mg/kg daily (maximum 60-80 mg) for 2-3 days 1, 2
• Two epinephrine auto-injectors with hands-on training 2, 4
• H1-antihistamine for 2-3 days 1
• H2-antihistamine twice daily for 2-3 days 1
• Written anaphylaxis action plan 3
• Allergist referral within 1-2 weeks 2

Critical Pitfalls to Avoid

• Never substitute steroids or antihistamines for epinephrine—delayed epinephrine is associated with fatalities. 3
• Never discharge prematurely—biphasic reactions are unpredictable and can occur up to 12 hours later. 2, 3
• Do not taper the 2-3 day steroid course—tapering is unnecessary for short courses. 2
• Be aware that rare allergic reactions to methylprednisolone itself can occur, particularly in asthmatics, though this is extremely uncommon. 6