IM Dexamethasone Dosing for Allergic Reaction in a 13.5 kg Girl
For a 13.5 kg girl with an allergic reaction, administer dexamethasone 1-2 mg/kg IM, which equals 13.5-27 mg (typically round to 15-25 mg as a practical dose). 1
Primary Treatment Considerations
Epinephrine remains the first-line treatment for anaphylaxis, not dexamethasone. 1, 2 If this allergic reaction meets criteria for anaphylaxis (skin/mucosal involvement PLUS respiratory compromise OR hypotension, or involvement of two or more organ systems), you must administer epinephrine 0.01 mg/kg IM (0.135 mg for this patient) immediately in the mid-outer thigh before or concurrent with dexamethasone. 2 For this 13.5 kg child, use the 0.15 mg epinephrine auto-injector if available (appropriate for 10-25 kg weight range). 1, 2
Dexamethasone Administration Details
- Dose: 1-2 mg/kg IM using the acetate salt formulation (must use acetate for IM route) 1
- Calculated dose: 13.5-27 mg for this 13.5 kg patient
- Practical dosing: Round to 15-25 mg based on available vial concentrations
- Route: Intramuscular injection 1
- Timing: Administer as adjunctive therapy after or concurrent with epinephrine if anaphylaxis is present 1
Clinical Algorithm for Decision-Making
Step 1 - Assess severity:
- Mild allergic reaction (isolated urticaria, pruritus): Dexamethasone may be primary treatment
- Moderate-to-severe or anaphylaxis (respiratory symptoms, hypotension, multi-system involvement): Epinephrine FIRST, dexamethasone as adjunct 1, 2
Step 2 - Administer medications:
- If anaphylaxis: Epinephrine 0.135 mg IM (or 0.15 mg auto-injector) immediately 2
- Then: Dexamethasone 15-25 mg IM 1
- Call 911/emergency services 2
Step 3 - Position and monitor:
- Place patient supine with legs elevated (unless respiratory distress/vomiting present) 2
- Monitor for at least 15 minutes after dexamethasone administration 1
- Be prepared to repeat epinephrine at 5-15 minutes if symptoms persist 2
Important Caveats and Pitfalls
Never delay epinephrine for dexamethasone administration - delayed epinephrine is associated with fatalities in anaphylaxis. 1, 2 Dexamethasone has a delayed onset of action and does not treat the immediate life-threatening manifestations of anaphylaxis. 1
Dexamethasone itself can rarely cause hypersensitivity reactions, including immediate IgE-mediated reactions and anaphylaxis, though the prevalence is estimated at only 0.3-0.5%. 3, 4 Rapid IV administration can cause perineal burning sensation, particularly in females, though this is not typically seen with IM administration. 5
Monitor for biphasic reactions - observe the patient for at least 6 hours as anaphylaxis symptoms may recur even after successful initial treatment. 2 The corticosteroid may help prevent late-phase reactions, though this remains an adjunctive benefit. 1
High-dose administration considerations: When using doses at the higher end of the range (approaching 2 mg/kg or 27 mg), ensure proper monitoring as higher corticosteroid doses carry increased risk of adverse effects, though these are generally minimal with single-dose administration. 6
Post-Treatment Management
Transport to emergency department for continued observation regardless of initial response. 2 Provide written anaphylaxis emergency action plan and prescribe epinephrine auto-injector (0.15 mg for this weight) for future episodes. 2 Arrange allergy referral for identification of trigger and long-term management planning. 2