drug eruptions

Question 1

describe a type 1 hypersensitivity reaction

Answer 1

• immediate

- involves IgE (antibody mediated)

Question 2

give an example of a type I hypersensitivity reaction

Answer 2

• atopic dermatitis
• anaphalaxis
• urticaria (hives)

Question 3

what is the most common type of drug eruption?

Answer 3

exanthematous drug eruption

Question 4

what type of hypersensitivity reaction are exanthematous drug eruptions?

Answer 4

Type IV hypersensitivity reaction

Question 5

describe a type II hypersensitivity reaction

Answer 5

-cytotoxic reaction mediated by IgG or IgM antibodies

Question 6

describe a type III hypersensitivity reaction

Answer 6

-reaction mediated by immune complexes

Question 7

describe a type IV hypersensitivity reaction

Answer 7

-delated reaction mediated by cellular response

Question 8

if a medication causes a skin eruption what usually occurs once the medication is withdrawn?

Answer 8

-the skin will usually go back to normal (however this is not always this case, half life plays a role and the ability of the drug to be retained/accumulate in tissue plays a role)

Question 9

how do exanthematous drug eruptions typically present?

Answer 9

• widespread symmetrically distributed rash
• mucous membranes usually spread
• pruritis (itch) is common
• mild fever is common
• skin pain
• erythema
• blisters, purpura, necrosis
• lymphadenopathy, arthralgia
• SOB, wheeze
• onset is usually 4 to 21 days after taking the drug
• usually mild and self limiting but can progress to a severe life threatening reaction!!

Question 10

what drugs tend to cause an exanthematous eruption?

Answer 10

• penicillins
• sulphonamides
• erythromycin
• streptomycin
• allopurinol
• anti epileptic drugs
• NSAIDs
• chloramphenicol

Question 11

what type of hypersensitivity reactions are urticarial drug reactions?

Answer 11

-Type I (IgE mediated)

Question 12

what does a palpable non blanching rash suggest?

Answer 12

-a purpuric vasculitis drug reaction

Question 13

how do fixed drug reactions present?

Answer 13

• well demarcated round/ovoid plaques
• red, painful
• resolves with pigmentation once the drug is stopped
• can re occur at same site on re exposure to drug
• can present as eczematous lesions, papule, vesicles or urticaria
• appears on hands, genitalia, lips and occasionally oral mucosa