What is the recommended follow-up for a patient with a rash given a Decadron (dexamethasone) injection in the office?

Management of Rash After Decadron (Dexamethasone) Injection in Office

Immediate Post-Injection Observation

Patients must remain in the office for at least 30 minutes after receiving any injection to monitor for immediate hypersensitivity reactions, as most severe reactions occur within this timeframe. 1

• The 30-minute observation period is the standard recommendation based on safety data showing that the majority of serious reactions occur within this window 1
• During this period, continuously assess for signs of progression including urticaria, pruritus, dyspnea, bronchospasm, hypotension, or angioedema 1
• If the rash appears during the observation period with any systemic symptoms (difficulty breathing, throat tightness, dizziness, chest discomfort), this represents a potential anaphylactic reaction requiring immediate treatment with epinephrine 0.3-0.5 mg intramuscularly 2, 3

Grading the Rash Severity

Grade 1-2 (Mild to Moderate): Localized rash, minimal skin changes, or dermatitis without systemic symptoms 1, 2

Grade 3-4 (Severe): Extensive rash with systemic symptoms such as hypotension, bronchospasm, angioedema, or signs of anaphylaxis 1, 2

Acute Management Based on Severity

For Mild Rash (Grade 1-2) Without Systemic Symptoms

• Administer a second-generation H1 antihistamine such as cetirizine 10 mg orally or loratadine 10 mg orally for symptomatic relief 3
• Avoid first-generation antihistamines like diphenhydramine in mild cases as they can cause sedation and may complicate assessment 3
• Apply topical high-potency corticosteroid (clobetasol propionate 0.05%) twice daily to affected areas 1
• Continue observation for an additional 15-30 minutes after treatment to ensure no progression 3

For Moderate to Severe Rash (Grade 2-3) or Any Systemic Symptoms

• Immediately administer diphenhydramine 50 mg IV plus ranitidine 50 mg IV (combined H1/H2 blockade) 4, 3
• Give methylprednisolone 100 mg IV for aggressive symptomatic control 4, 3
• Do not attempt to give additional dexamethasone, as the rash itself may represent a delayed-type hypersensitivity reaction to dexamethasone 5
• Monitor vital signs continuously and maintain IV access 3
• Observe for at least 24 hours if Grade 3 reaction 2

For Anaphylaxis (Grade 4)

• Administer epinephrine 0.3-0.5 mg (1:1000) intramuscularly into the lateral thigh immediately, repeating every 5-15 minutes as needed 2, 3
• Provide rapid fluid resuscitation with 1-2 liters normal saline 3
• Give adjunctive medications: diphenhydramine 50 mg IV, ranitidine 50 mg IV, and methylprednisolone 1-2 mg/kg IV 3
• Call emergency medical services and transfer to emergency department 2

Patient Education and Discharge Instructions

Educate patients about delayed and biphasic reactions, which can occur 2-24 hours after the initial exposure, though these are typically less severe than the initial reaction. 1

• Instruct patients to immediately return or call 911 if they develop difficulty breathing, throat swelling, severe dizziness, chest pain, or worsening rash within 24 hours of leaving the office 1
• Delayed systemic reactions can occur after the 30-minute observation period in up to 38% of cases, though most are mild 1
• Biphasic reactions (recurrence after initial resolution) occur in up to 23% of patients who experience systemic reactions, typically within 24 hours 1
• Prescribe oral antihistamines (cetirizine 10 mg daily or loratadine 10 mg daily) for 3-5 days to manage ongoing pruritus 3
• Provide topical high-potency corticosteroid cream for continued application twice daily until rash resolves 1

Documentation and Future Contraindications

Document "dexamethasone allergy" clearly in the patient's medical record and inform the patient that dexamethasone should be permanently avoided in all forms (oral, IV, IM, topical). 3, 5

• Cross-reactivity can occur with structurally similar corticosteroids including betamethasone and fluocortolone 5
• Alternative corticosteroids from different structural groups (such as methylprednisolone, hydrocortisone, or prednisone) may be tolerated, but this requires formal allergy testing before use 5
• Consider referral to an allergist for comprehensive corticosteroid allergy testing if future corticosteroid use is anticipated 3
• Measure serum tryptase levels 15 minutes to 3 hours after onset if anaphylaxis occurred, as this can help confirm the diagnosis 3

Critical Pitfalls to Avoid

• Never delay epinephrine administration if anaphylaxis is suspected—waiting to see if symptoms improve can result in cardiovascular collapse 2, 3
• Do not use corticosteroids alone without antihistamines for acute allergic reactions, as combination therapy provides optimal symptom control 4, 3
• Do not allow patients to leave before 30 minutes even if they feel fine, as severe reactions can develop suddenly within this window 1
• Do not rechallenge with dexamethasone after a Grade 3-4 reaction, as this represents an absolute contraindication to future use 3
• Avoid prescribing oral corticosteroids for discharge in simple urticarial reactions, as evidence suggests this may prolong urticaria activity without providing benefit 6