Drug Eruptions

Question 1

what mediates type 2 ‘allergic’ reactions

Answer 1

cytotoxic (cytotoxic t cells activated)

Question 2

what skin symptoms are common with type 2 reactions

Answer 2

pemphigus and pemphigoid

Question 3

what mediates type 3 reactions

Answer 3

immune complex mediated reaction

Question 4

what skin symptoms are common with type 3 reactions

Answer 4

purpura/ rash

Question 5

what mediates type 4 reactions

Answer 5

cell mediated delayed hypersensitivity reactions- T cell mediated

Question 6

what skin symptoms are associated with type 4 reactions

Answer 6

erythema/ rash

Question 7

are drug immunologically mediated reactions dose dependent

Answer 7

not dose dependent

Question 8

what non allergic skin reactions can be caused by drugs

Answer 8

eczema, 
drug- induced alopecia,
phototoxicity, 
skin erosions due to 5-fluorouracil, 
atrophy (steroids), 
psoraisis, 
pigmentation, 
cheilitis, 
xerosis

Question 9

what is exanthematous, describe the pathophysiology ans symptoms

Answer 9

generalised symmetrical macropapular rash/ morbilliform/ macropapular

idiosyncratic, T cell mediated delayed (4-21 days after taking drug) type 4 hypersensitivity

mild and self limiting, itch and mild fever common

can progress to life threatening

Question 10

what are the different presentations of drug eruptions

Answer 10

exanthematous, 
urticarial,
papulosquamous,
pustular,
bullous,
pigmentation,
itch/pain,
photosensitivity

Question 11

drug eruptions usually resolve when the drug is withdrawn, what are the exceptions to this rule

Answer 11

the half life of the drug, ability of the drug to be retained/ accumulate, cross reactions with similar class of drugs

Question 12

what are the risks factors for drug eruptions

Answer 12

age (young adult/ elderly take more)
genetics (polymorphism in gene that metabolise drugs)
concomitant disease (immunosuppressed- HIV, cystic fibrosis)

Question 13

name two drug types that commonly cause eruptions

Answer 13

B lactam compounds, NSAIDs

Question 14

what is the most common type of drug reactions

Answer 14

exanthematous

Question 15

what are the indicators of a potentially severe exanthematous drug eruption

Answer 15

involvement of mucous membrane and face

facial erythema and oedema

widespread confluent erythema

fever >38.5

skin pain

blisters, purpura, necrosis

lymphadenopathy, arthralgia

SOB, wheezing

Question 16

what drugs are associated with exanthematous eruptions

Answer 16

penicillins
sulphonamides 
erythromycin
streptomycin
allopurinol
anti-epileptics 
NSAIDs
chloramphenicol

Question 17

does exanthematous skin reaction blanche

Answer 17

yes

Question 18

does purpuric vasculitic reactions blanche

Answer 18

no

Question 19

describe a urticarial drug reaction

Answer 19

immediate IgE mediated hypersensitivity reaction after rechallenge with drug

OR

direct release of inflammatory mediators from mast cells on first exposure

Question 20

what drugs are associates with a urticarial drug reaction

Answer 20

rechallenge; B-lactam antibiotics, carbamepine

first exposure; aspirin, opiates, NSAIDs, muscle relaxants, vancomycin, quinolones

Question 21

what might urticaria that persists be

Answer 21

urticarial vasculitis

Question 22

what is the usual timeline for urticaria

Answer 22

comes and goes within hours, will be gone in 24 hours

Question 23

what can cause anceiform drugs reactions

Answer 23

glucocorticoids, androgens, lithium, isoniazid, phenytoin

Question 24

what can cause an acute generalised exanthematous pustulosis (AGEP)

Answer 24

rare, antibioticsm calcium channel blockers, antimalarials

Question 25

what can cause drug induced bullous pemphigoid

Answer 25

ace inhibitors, penicillin, furosemide

Question 26

what drug can cause a blistering rash in ring forms and why

Answer 26

vancomycin- linear decrease of IgE

Question 27

describe fixed drug eruptions

Answer 27

well demarcated round/ovoid plaques, red/purple-ish and painful affecting hands, genitalia, lips, oral mucosa and buttocks

Question 28

what happens to a fixed drug reaction when the drug is stopped

Answer 28

resolves with persistent pigmentation

Question 29

for fixed drug reactions what happens after resolutions if the drug is used again

Answer 29

will occur in exactly the same spot

Question 30

what often causes fixed drug reactions

Answer 30

treatment for (period) pain e.g paracetamol, NSAIDs aslo tetracycline, doxycycline, carbamazepine

Question 31

name four severe cutaneous adverse drug reactions

Answer 31

steven-johnson syndrome (SJS) toxic epidermal necrolysis (TEN) drug reaction with eosinophilia and systemic symptoms (DRESS) - high fever, extensive symmetrical rash, facial oedema acute generalised exanthemaout pustulosis (AGEP)

Question 32

what are the symptoms of SJS

Answer 32

generalised erythema and erosions of oral mucosae

Question 33

what are the acute phototoxic drug reactions

Answer 33

skin toxicity (photosensitivity), system toxicity, photodegradation

Question 34

what are the chronic phototoxic drug reactions

Answer 34

pigmentation, photoaging, photocarcinogenesis

Question 35

why do drugs cause photoxic drug reactions

Answer 35

7/10 drugs absorb light, cause hypersensitivity, are degraded producing photo products and oxygen radicals

Question 36

are phototoxic cutaneous drug reactions immunological

Answer 36

no

Question 37

what are the patterns of skin toxicity

Answer 37

immediate prickling with delayed erythema and pigmentation exaggerated sunburn exposed telangiectasia delayed 3-5 days erythema and pigmentation increased skin fragility- scarring and blistering

Question 38

what drugs are associated with phototoxicty

Answer 38

``` antibiotics thiazides chlorpromazine NSAIDs quinine antifungals immunosuppressants (loads more) ```

Question 39

what are the common culprits of phototoxicity drug reactions

Answer 39

doxycycline, amiodarone, chlorpomazine, quinine

Question 40

what causes telangiectasia and angioemas on sun exposed sights

Answer 40

calcium antagonist phototoxicity

Question 41

what can proton pump inhibitors cause (phototoxicity)

Answer 41

sub acute cutaneous lupus

Question 42

can skin prick testing be used for type 2 and 3 reactions

Answer 42

no may trigger SJS, TEN and DRESS

Question 43

what is the management for drug reactions

Answer 43

discontinue drug if possible, use alternative topical corticosteroids may be helpful antihistamines if type 1 (or if itch)