Drug allergy

Classification according to timeline
- Immediate (< 1 hour)
  - Urticaria
  - Angioedema
  - Rhinitis
  - Bronchospasm
  - Anaphylaxis
- Non-immediate (> 1 hour)
  - Delayed urticaria
  - Maculopapular exanthema
  - Erythroderma
  - Vasculitis
  - Stevens-Johnson syndrome (SJS)
  - Toxic epidermal necrolysis (TEN)
  - Drug reaction with eosinophilia and systemic symptoms (DRESS)
  - Acute generalized exanthematous pustulosis (AGEP)
  - Symmetrical drug-related intertriginous and flexural exanthemas (SDRIFE)
Classification according to pathomechanism
- Type I hypersensitivity
  - IgE-mediated mast cell activation as a reaction to a soluble antigen
  - All immediate drug allergies
  - Treatment
    - Eliminate culprit drug
    - Antihistamines
- Type III hypersensitivity
  - IgG-mediated complement activation as a reaction to a soluble antigen
  - Vasculitis
  - Serum sickness
- Type IVa hypersensitivity
  - Cell-mediated macrophage activation as a reaction to a presented antigen
  - Tuberculin reaction
  - Contact dermatitis
- Type IVb hypersensitivity
  - Cell-mediated eosinophil activation as a reaction to a presented antigen
  - DRESS
  - Maculopapular exanthema
  - Erythroderma
- Type IVc hypersensitivity
  - Cell-mediated T-cell activation as a reaction to a presented antigen
  - Stevens-Johnsons syndrome
  - Toxic epidermal necrolysis
- Type IVd hypersensitivity
  - Cell-mediated neutrophils activation as a reaction to a presented antigen
  - AGEP
Drug-induced urticaria
- Drugs
  - Penicillin
  - Aspirin
  - NSAIDs
Angioedema/Quincke-oedema
- Drugs
  - NSAIDs
  - Aspirin
  - ACE-inhibitors (not technically a drug allergy)
- Clinical features
  - Facial oedema
  - If laryngeal involvement – dyspnoea, inspiratory stridor
- Treatment
  - Epinephrine
  - Steroids
  - Antihistamines
Anaphylaxis
- Drugs
  - Lidocaine
  - Anaesthetics
  - Aspirin
  - Contrast
  - NSAIDs
- After minutes – hours
- Clinical features
  - Hypotension
  - Bronchospasm, laryngeal oedema -> dyspnoea, inspiratory stridor
- Treatment
  - Epinephrine
  - Steroids
  - Antihistamines
Drug-induced vasculitis
- Drugs
  - Antibiotics
  - Analgesics
- Clinical features
  - Painful, palpable purpura
  - Urticaria
- Resolve after drug cessation
Serum sickness
- Drugs
  - NSAIDs
  - Penicillins
- Clinical features
  - Fever
  - Rash
  - Arthralgia
- Resolve after drug cessation
Maculopapular exanthema
- On trunk, extremities
- No eosinophilia
- No systemic symptoms
- Resolve after drug cessation
Erythroderma
- Erythema, scaling of the whole body
- Eosinophilia
- No systemic symptoms
- Resolve after drug cessation