What is the treatment for a drug-induced allergic reaction?

Treatment of Drug-Induced Allergic Reactions

For immediate drug-induced allergic reactions, especially anaphylaxis, epinephrine 0.01 mg/kg intramuscularly in the mid-outer thigh is the first-line treatment and must be administered immediately, with repeat doses every 5-10 minutes as necessary. 1, 2

Immediate Reactions (Within 1 Hour)

Recognition and Initial Management

Immediate reactions present with cutaneous manifestations (urticaria, pruritus, flushing, angioedema), respiratory symptoms (dyspnea, wheeze, rhinorrhea, upper airway angioedema), cardiovascular collapse (hypotension, tachycardia, syncope), and gastrointestinal symptoms (nausea, vomiting, diarrhea, cramping). 3, 1

Epinephrine administration:

• Adults and children ≥30 kg: 0.3-0.5 mg (0.3-0.5 mL) intramuscularly in the anterolateral thigh, maximum 0.5 mg per injection 2
• Children <30 kg: 0.01 mg/kg (0.01 mL/kg) intramuscularly in the anterolateral thigh, maximum 0.3 mg per injection 2
• Inject through clothing if necessary, hold the child's leg firmly to prevent movement 2
• Repeat every 5-10 minutes as clinically indicated 1, 2
• Use a needle at least 1/2 to 5/8 inch long to ensure intramuscular delivery 2

Critical Pitfall to Avoid

Delayed epinephrine administration increases morbidity and mortality. 1 The lateral thigh (vastus lateralis) produces the most rapid rise in serum epinephrine levels compared to other injection sites. 4

Adjunctive Therapy

After epinephrine, provide:

• Antihistamines (H1-blockers like diphenhydramine) for symptomatic relief of urticaria and pruritus 1, 5
• Corticosteroids (systemic) to prevent biphasic reactions, which can occur hours after initial symptom resolution 1, 5
• Bronchodilators if bronchospasm persists despite epinephrine 6
• Intravenous fluids for hypotension and cardiovascular support 6

Observation Period

Monitor patients for at least several hours after treating anaphylaxis due to risk of biphasic reactions, particularly in those with initially severe symptoms or delayed epinephrine administration. 1 Patients on beta-blockers or ACE inhibitors require especially close monitoring as these medications increase severity of anaphylactic reactions and reduce epinephrine effectiveness. 1

Delayed Reactions (>1 Hour After Administration)

Mild to Moderate Reactions

For maculopapular exanthema and localized skin reactions:

• Immediately discontinue the suspected culprit drug 1, 6
• Topical corticosteroids for localized skin manifestations 1, 6, 5
• Oral antihistamines for pruritus 1, 6, 5

Severe Delayed Reactions

For DRESS (Drug Reaction with Eosinophilia and Systemic Symptoms), Stevens-Johnson Syndrome (SJS), or Toxic Epidermal Necrolysis (TEN):

• Immediate drug discontinuation is essential 1, 6
• Systemic corticosteroids (0.5-2 mg/kg/day tapered over 4-6 weeks for severe reactions) 3
• Transfer to specialized care (burn unit or intensive care for SJS/TEN) 1, 6
• Intravenous immunoglobulin may be considered for severe cases 5

Chemotherapy-Related Reactions

Platinum Agents (Carboplatin, Cisplatin, Oxaliplatin)

Reactions typically occur after multiple exposures or at completion of initial therapy (cycle 6). 3

If mild reaction occurred previously:

• Great caution is required; consultation with an allergist is recommended 3
• Patients may develop more serious reactions even with slow infusion 3
• Desensitization protocols should be considered if the drug is essential and no alternative exists 3

If severe life-threatening reaction occurred:

• The implicated drug should not be used again 3

Taxanes (Paclitaxel, Docetaxel)

Reactions typically occur during first few cycles but can occur at any time. 3

For mild infusion reactions (flushing, rash, chills):

• Stop the infusion immediately 3
• May rechallenge with slower infusion rate if patient, physician, and nursing staff are comfortable 3
• Ensure emergency equipment is available 3
• This slow reinfusion differs from formal desensitization 3

Immune Checkpoint Inhibitors (ICIs)

For severe immune-related adverse events:

• Stop the ICI 3
• Systemic corticosteroids 0.5-2 mg/kg/day tapered over 4-6 weeks 3
• Disease-specific immunomodulators if no improvement on corticosteroids or flare during taper 3
• Grade 4 reactions are typically contraindications to rechallenge 3

EGFR Tyrosine Kinase Inhibitors

For acneiform eruptions and skin toxicity:

• Topical and systemic corticosteroids 3
• Antibiotics (minocycline or doxycycline) for prevention and treatment of superinfected lesions 3
• Dose reduction or temporary discontinuation with reintroduction at lower dose once symptoms improve 3
• Immediate discontinuation if bullous or exfoliative skin rash develops 3

Long-Term Management

After any drug-induced allergic reaction:

• Document the reaction in the patient's medical record and provide an "allergy passport" 6
• Prescribe epinephrine auto-injectors for patients at risk of future anaphylaxis 6, 5
• Educate patients on recognition of early symptoms, when to use epinephrine, and hidden allergens in medications 3, 6
• Refer to an allergist for comprehensive evaluation, skin testing (when available), and identification of safe alternatives 6, 7
• Consider cross-reactivity when selecting alternative medications (e.g., 4% of penicillin-allergic patients react to cephalosporins) 3

Prophylaxis Considerations

For patients requiring re-exposure to drugs that previously caused reactions:

• Desensitization protocols can induce temporary tolerance but must be repeated if the drug is needed again in the future 3, 7
• Premedication with corticosteroids and antihistamines markedly reduces recurrent anaphylactoid reactions to radiocontrast media 3

Standing orders and preparedness:

• Treatment areas must have emergency equipment and standing orders for immediate intervention 3
• All staff should be prepared for drug reactions with every infusion 3