Module 13.1 - Drug Eruptions

Question 1

What are drug eruptions?

Answer 1

• Any adverse skin cutaneous reaction, usually caused by medications, either topical, oral or parenteral.
• Allergic reactions require prior exposure to medication.
• Drug induced exanthems (morbilliform eruptions) account for 75% of all drug reactions; mostly due to antibiotics and sulfonamindes
• Less frequently, may cause urticarial, angioedema, anaphylaxis, hypersensitivity vasculitis, phototoxic and photoallergic reactions; mostly due to anti-seizure meds and sulfonamides

Question 2

Describe a type I allergic reaction

Answer 2

Type I:

• immediate type immunologic reaction (IgE)
• associated with urticarial, angioedema, hypotension (anaphylaxis)

Question 3

Describe a type II allergic reaction

Answer 3

Type II:

• Cytotoxic reaction
• Medication or causative agent causes lysis of cells with antibody production

Question 4

Describe a type III allergic reaction

Answer 4

Type III:

• Drug induced vasculitis; IgG or IgM mediated
• Associated with vasculitis, urticarial, arthritis, nephritis, hemolytic anemia, thrombocytopenia and agranulocytosis

Question 5

Describe a type IV allergic reaction

Answer 5

• Cell mediated immune reaction
• Drug reaction with eosinophilia and systemic syndromes (DRESS)- severe idiosyncratic reaction characterized by fever, malaise, LAD and skin eruption
• Presents as hepatitis, eosinophilia, pneumonia, Lymphadenopathy and/or nephritis
• Symptom during 2-6 weeks after medication administration
• Associated with seizure medications, beta blockers and allopurinol

Question 6

What antibiotics commonly cause urticarial and maculopapular allergic cutaneous reactions?

Answer 6

Bactrim (TMP-SMZ) & penicillins

Question 7

What are some common drug allergic reactions?

Answer 7

• ‘Red Man’ syndrome associated with rapid vancomycin administration; usually resolves with rate reduction
• ACE inhibitors associated with chronic cough and angioedema
• B-blockers associated with worsening of asthma due to blocking the action of epinephrine
• Phototoxic eruptions – most common drug induced photo eruptions; caused by absorption of ultraviolet light by the causative drug which releases energy and damages cells
• Stevens-Johnson syndrome (Toxic epidermal necrolysis with severe mucocutaneous eruptions): associated with sulfonamides and anti-seizure medications; causes epidermal necrosis and sloughing of the mucous membranes and skin
• Intravenous contrast and opioids- stimulate mast cell histamine release through a non-IgE mediated reaction – 20-30% will have recurrent reactions

Question 8

What are some subjective/physical exam findings associated with drug reactions?

Answer 8

• Abrupt onset
• May be associated with:
  
  • Bright confluent erythema – most common finding
  • Pruritis
  • Angioedema
  • Tongue swelling
  • Fever/chills
  • Erythema
  • Arthralgias
  • Shortness of breath, wheezing, hypotension
  • Morbilliform or maculopapular eruptions- most commonly on trunk; can develop into exfoliative dermatitis if medication not discontinued
  • photodermatitis

Question 9

What are false drug reactions?

Answer 9

• Adverse reactions are not drug reactions- nausea/vomiting, weight gain
• Patient records should be corrected when true allergy has not occurred

Undetermined reactions of childhood may not be reproducible as an adult

Question 10

What lab/diagnostic tests are used to diagnose a drug reaction/allery?

Answer 10

• Diagnosis made on clinical presentation usually
• Eosinophil count > 1000/microliter
• Consider skin biopsies- in rare cases
• Allergy skin testing- should NOT be performed during flare
• Challenge dosing- monitored, oral dosing, if an anaphylactic reaction seems unlikely to occur

Question 11

How do you manage a drug reaction?

Answer 11

• Discontinue causative medication
• Treatment aimed at symptom control
• Epinephrine 1:1000, 0.5-1 ml IV or SQ for rapid temporary relief of urticarial and/or angioedema; repeat every 20 minutes x 3 doses if needed
• Life threatening reactions: Epinephrine 1:10,000, 0.5-1 mg IV/ET/IO
• Oral/IV anti-histamine:
  
  • Diphenhydramine 25-50mg IV every 6 hours x 3-5 days, may follow epinephrine
  • Ranitidine (H2 blocker) 50mg IV once, followed by 150mg po bid x 3 days if needed
• Corticosteroids- not routinely indicated
  
  • IN severe reactions: use systemic corticosteroids and taper slowly
  • Prednisone (or equivalent) 1 mg/kg po daily x 7 days
• Bronchodilators, inhaled or B2 agonists- for wheezing if indicated
• Treatment of dermatitis- consult dermatology if extensive blistering or TEN present