Drug Reactions and Blistering Disorders Flashcards
What are the characteristics of most cutaneous drug reactions?
inflammatory
generalized
symmetric
What are the most common and important types of adverse drug reactions?
exanthematous
drug-induced hypersensitivity syndrome (DIHS), also called Drug-related eosinophilia with systemic symptoms (DRESS)
epidermal necrolysis - Stevens-Johnson Syndrome, and Toxic Epidermal Necrolysis (TEN)
immediate drug-induced skin reactions
occur less than 1 hour of the last adminstered dose
- urticaria
- angioedema
- anaphylaxis
delayed drug-induced reactions
occurs after one hour, but usually more than 6 hours (and occasionally weeks to months after the start of administration)
- exanthematous eruptions
- fixed drug eruption
- systemic reactions (DRESS, SJS, TEN)
- vasculitis (may also be systemic)
What is the use of allergy testing for drug reactions?
limited value in evaluating adverse cutaneous rections to medications
penicillin is the exception - skin testing is the preferred method of evaluation of possible type I, IgE-mediated penicillen allergy (urticaria)
What are the important questions in a drug history?
seven I’s:
1) instilled (eye drops, ear drops)
2) inhaled (steroids, beta adrenergic)
3) ingested (capsules, tablets, syrup)
4) inserted (suppositories)
5) injected (IM, IV)
6) incognito (herbs, non-traditional medicine, homeopathic, vitamins, over-the-counter)
7) intermittent (patients may not reveal medications they take on an intermittent basis unless specifically asked)
What are the uses of a drug timeline?
most important data in determining if a rash is meidcation-related
start with onset of the rash as Day 0, and work backwards and forwards
for exanthematous drug eruptions, the initiation of the medication is often 7-10 days before the rash (may be much shorter for repeate exposrues)
What are some risk factors for drug reactions?
female
prior history of drug reaction
recurrent drug exposure
HLA type
certain disease state (EBC - aminopenicillins, HIV - sulfonamides)
exanthem
a rapidly erupting rash that may have specific diagnostic features of an infectious disease
usually referring to the rashes seen with viral/coccal infections
What are the classic diseases with exanthematous rashes?
chickenpox
measles
roseola infantum
rubella
What is the classic progression of measles?
starting on head, spreading down the body “like a can of pain would”
What is the exanthem characteristic of roseola infantum?
caused by HHV 6
starts with high fever and often ends abruptly
happens about the same time as a pinkish-red flat or raised rash that appears on the trunk and spreads over the body
exanthematous drug eruption
most common of all cutaneous drug eruptions
limited to the skin
lesions intially appear on the trunk and spread centrifugally to the extremities in a systemic fashion
erythematous macules and papules
pruritis and mild fever may be present
skin lesions usually appear more than 2 days after the drug has been started, mainly around 7-10, and occasionally persists 2-3 dys after havving stopped the drug
What is the clinical course and treatment of exthematous reactions?
resolves in a few days to a week after the medication is stopped
can continue the medication if the eruption is not too severe, but use with caution
resolves without sequelae (though scaling/desquamation can occur)
treatment consists of topical steroids, oral antihistamines, and reassurance
What is Drug-Induced Hypersensitiviety Syndrome?
also known as Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)
skin eruption with systemic symptoms (ex. fever) and internal organ involvement
more than 70% of patients have an eosinophilia
What are the typical signs and symptoms of Drug-Induced Hypersensitivity Syndrome?
macular exanthem
erythematous centrofacial swelling
fever
malaise
lymphadenopathy
involvement of other organs such as liver or kidney
What is the clinical course of DRESS?
signs and symptoms typically begin in the 3rd week after starting the mediction or increasing dose
signs and symptoms may persist and recur for many weeks even after cessation of drug treatment
fatality rate may be up to 10%
medications implicated in DRESS
allopurinol
antibiotics
anti-TB drugs
anticonvulsants
NSAIDs
Anti-HIV drugs
What is the approach to the patient with suspected DRESS?
stop (or substitute) all suspect medications and discontinue non-essential medications
What is the treatment for DRESS?
stop medication if severe
also use systemic sterids if severe - gradually taper
if not, use topical steroids and systemic antihistamines
What is erythema multiforme?
self-limited but potentially recurrent disease
abrupt onset of papular “target” lesions, with vast majority of lesions appearing within 24 hours
target lesions favor acrofacial sites
erythema multiforme minor
papular target lesions with little or no mucosal involvement and no systemic symptoms
erythema multiforme major
papular target lesions with severe mucosal involvement and systemic features
What are the most common precipitating factors of erythema multiforme?
preceding HSV or mycoplasma pneumoniae infections are the most common precipitating factors
NOT usually a drug reaction
erythema multiforme does not carry the risk of progression to toxic epidermal necrolysis
