Drug Eruptions Flashcards
what mediates type 2 ‘allergic’ reactions
cytotoxic (cytotoxic t cells activated)
what skin symptoms are common with type 2 reactions
pemphigus and pemphigoid
what mediates type 3 reactions
immune complex mediated reaction
what skin symptoms are common with type 3 reactions
purpura/ rash
what mediates type 4 reactions
cell mediated delayed hypersensitivity reactions- T cell mediated
what skin symptoms are associated with type 4 reactions
erythema/ rash
are drug immunologically mediated reactions dose dependent
not dose dependent
what non allergic skin reactions can be caused by drugs
eczema, drug- induced alopecia, phototoxicity, skin erosions due to 5-fluorouracil, atrophy (steroids), psoraisis, pigmentation, cheilitis, xerosis
what is exanthematous, describe the pathophysiology ans symptoms
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
what are the different presentations of drug eruptions
exanthematous, urticarial, papulosquamous, pustular, bullous, pigmentation, itch/pain, photosensitivity
drug eruptions usually resolve when the drug is withdrawn, what are the exceptions to this rule
the half life of the drug, ability of the drug to be retained/ accumulate, cross reactions with similar class of drugs
what are the risks factors for drug eruptions
age (young adult/ elderly take more)
genetics (polymorphism in gene that metabolise drugs)
concomitant disease (immunosuppressed- HIV, cystic fibrosis)
name two drug types that commonly cause eruptions
B lactam compounds, NSAIDs
what is the most common type of drug reactions
exanthematous
what are the indicators of a potentially severe exanthematous drug eruption
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
what drugs are associated with exanthematous eruptions
penicillins sulphonamides erythromycin streptomycin allopurinol anti-epileptics NSAIDs chloramphenicol
does exanthematous skin reaction blanche
yes
does purpuric vasculitic reactions blanche
no
describe a urticarial drug reaction
immediate IgE mediated hypersensitivity reaction after rechallenge with drug
OR
direct release of inflammatory mediators from mast cells on first exposure
what drugs are associates with a urticarial drug reaction
rechallenge; B-lactam antibiotics, carbamepine
first exposure; aspirin, opiates, NSAIDs, muscle relaxants, vancomycin, quinolones
what might urticaria that persists be
urticarial vasculitis
what is the usual timeline for urticaria
comes and goes within hours, will be gone in 24 hours
what can cause anceiform drugs reactions
glucocorticoids, androgens, lithium, isoniazid, phenytoin
what can cause an acute generalised exanthematous pustulosis (AGEP)
rare, antibioticsm calcium channel blockers, antimalarials
what can cause drug induced bullous pemphigoid
ace inhibitors, penicillin, furosemide
what drug can cause a blistering rash in ring forms and why
vancomycin- linear decrease of IgE
describe fixed drug eruptions
well demarcated round/ovoid plaques, red/purple-ish and painful affecting hands, genitalia, lips, oral mucosa and buttocks
what happens to a fixed drug reaction when the drug is stopped
resolves with persistent pigmentation
for fixed drug reactions what happens after resolutions if the drug is used again
will occur in exactly the same spot
what often causes fixed drug reactions
treatment for (period) pain e.g paracetamol, NSAIDs
aslo tetracycline, doxycycline, carbamazepine
name four severe cutaneous adverse drug reactions
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)
what are the symptoms of SJS
generalised erythema and erosions of oral mucosae
what are the acute phototoxic drug reactions
skin toxicity (photosensitivity),
system toxicity,
photodegradation
what are the chronic phototoxic drug reactions
pigmentation,
photoaging,
photocarcinogenesis
why do drugs cause photoxic drug reactions
7/10 drugs absorb light, cause hypersensitivity, are degraded producing photo products and oxygen radicals
are phototoxic cutaneous drug reactions immunological
no
what are the patterns of skin toxicity
immediate prickling with delayed erythema and pigmentation
exaggerated sunburn
exposed telangiectasia
delayed 3-5 days erythema and pigmentation
increased skin fragility- scarring and blistering
what drugs are associated with phototoxicty
antibiotics thiazides chlorpromazine NSAIDs quinine antifungals immunosuppressants (loads more)
what are the common culprits of phototoxicity drug reactions
doxycycline, amiodarone, chlorpomazine, quinine
what causes telangiectasia and angioemas on sun exposed sights
calcium antagonist phototoxicity
what can proton pump inhibitors cause (phototoxicity)
sub acute cutaneous lupus
can skin prick testing be used for type 2 and 3 reactions
no may trigger SJS, TEN and DRESS
what is the management for drug reactions
discontinue drug if possible, use alternative
topical corticosteroids may be helpful
antihistamines if type 1 (or if itch)
