Drug rxns Flashcards
4 main types of drug rxns
exanthematous
fixed drug rxn
drug induced hypersensitivity
epidermal necrolysis
immediate vs delayed rxn
immediate- less than one hour like urticaria, angioedema, anaphylaxis
delayed- after one hour but less than 6 usually
risk factors for drug rxn
female
prior hx
recurrent exposure
HLA type
EBV infections (more rxn to aminopenicillin), HIV (to sulfonamides)
exanthematous drug eruption
most common drug rxn, lmitied to skin - widespread and symmetric beginning on trunk usually
erythematous macules and infiltrated (something deeper) papules
pruritis and mild fever
time course for exanthematous
starts over 2 days later, may stop around day 8-11
tx for exanthematous
topical steroid
antihistamines
fixed drug eruption
formation of solitary/localized erythematous patch or plaque that will recur at same site w/ re exposure to drug
common causes of fixed drug
NSAIDS
tetracyclines
metro
sulfonamides
fixed drug morpho
often mouth, genitalia, acral areas
sharply demarcated, eryth macules evolve to plaques, can have bullae or erosions
healed are dark brown/violet
tx for fixed drug
self resolve days to weeks
non eroded can tx w/ topical steroid
eroded can tx w/ topical abx and dressing
refer if widespread or generalized
what to order/suspect w/ rash and facial edema
CBC and LFTs- eosinophilia and atypical lypmphs
elevated AST
suspect drug induced hypersensitivity syndrome (DIHS or DRESS-drug rxn w/ eosinophila and systemic sx)
DIHS pres
skin eruption w/ systemic sx and internal organ involvement
macular exanthem, erythematous centrofacial swelling, fever, malaise, lymphadenopathy, other organs like liver
most have eosinophilia
timing of DIHS
usually 3 weeks after start of med or increasing dose (exanthematous appears in 7-10 days)
signs and sx persist
meds implicated in DIHS
allopurinol abx- sulfa and penicillin anticonvulsants (phenytoin) NSAIDs abacavir (HIV)
approach to DIHS
organ systems? LFTs, BUN, Cr, CBC
which drug?
stop/sub meds
topical steroids and anti H if mild
systemic steroids usually- aorund 3 mos w/ slow taper
contast SJS and TEN
less than 10% of body area= SJS, more than 30 is TEN
pres of SJS/TEN
extensive necrosis and detachment of epidermis and mucosal surface, very painful
prodrome of fever, headache, myalgias
mortality due to sepsis and respiratory failure
common drugs w/ SJS/TEN
sulfas allopurinol tetracycline anticonvulsant NSAIDs
mnemonic SATAN
timeline of SJS/TEN
w/i 8 weeks of drug exposure
sites of SJS /TEN
symmetric and distributed on face trunk and proximal extremities, rapid expansion
skin findings of SJS/TEN (4)
erythematous irregular shaped dusky red macules, progressive coalescence
mucus membrane involvement is key for this dx
skin can detach in sheets, detaches w/ lateral pressure (nikolsky sign)
atypial target lesions w/ dark center, may blister
SJS/TEN complication
corneal damage
fluid electolyte and nutriion problems
bactermia and sepsis
mucous membrane stenosis/scarring
tx of SJS/TEN
supportive care and removal of offending drugs
care in burn unit w/ high BSA
contrast erythema multiforme w/ SJS
sometimes on spectrum, can also have mucosal involvement
more acral and extremities over trunk
usually HSV rather than drug trigger
erupts after 72 hrs, lasts 2 weeks
