Cutaneous Drug eruptions Flashcards
Why is time an important consideration when drug eruptions occur?
Cutaneous eruption will occur due to drug commenced in prev 6 wks
Most serious eruption occur during first prolonged exposure, onset of drug reaction will be more rapid after re-exposure
Reactions may occur after dose modification, interacting drug introduced, or development of renal/liver impairment
Can occur days/weeks after drug removed and can last for days after drug has been removed
What should be done if a drug rash is suspected?
Take full hx = meds (question patient about all meds), establish drug timeline
Onset of rash is day 0 and work backwards and dorwards
What is classed as an immediate drug reaction?
Occurs in <1hr after last dose
Mediated by IgE
Sx = urticaria, angioedema
What is classes as a delayed drug reaction?
Occurs after 1 hr but usually more than 6 hrs after last dose
Can occur wks to months after start of med
Mediated by IgG, immune complex, or T cells
e.g. SJS, TEN, vasculitis, fixed drug eruption, exanthematous eruption
What are some risk factors to cutaneous drug eruptions?
Female
Prior hx of drug reaction
Recurrent drug exposure
HLA type (human leukocyte antigen)
Certain disease states (e.g) HIV patients
What is a exanthematous drug eruption? (what is? when occur? What meds cause? characteristics?)
Aka = morbilliform drug eruption or maculopapular eruption - most common of all drug eruptions
When = W/in 7-10 days of exposure, may be faster 1-3 days
Characteristics = Can be associated w/ fever or itch, skin peeling
- starts w/ trunk and spreads to limbs and neck = bilateral and symmetrical
Adults = meds
child = viral
Cause = abx
What is a fixed drug eruption? (what is? when occur? What meds cause? characteristics?)
Occurs at same site/s w/ re-exposure to drug, up to 2 wks after first exposure or faster for future exposure
Characteristics = well-defined round, oval patch of redness and swelling, sometime blister, can be painful
Cause = paracetamol, NSAIDs, tetracycline, sulfonamides, salicylates, metronidazole, hyoscine butyl bromide, yellow food colouring
Resolve = days to weeks after drug stopped
How can fixed drug eruptions be treated?
Removal of drug and potent topical steroid on unbroken lesions
Broken lesions = cover w/ protective dressing until healed
How is an exanthematous drug eruption treated?
Resolves when meds are w/drawn
Emollients + potent topical steroids
Oral antihistamines
Reassurance
What is a photosensitivity drug eruption/ADR? (what is? when occur? What meds cause? characteristics?)
Prominent on sun-burnt sites = face, hands, V of neck, may spread to unexposed areas in photoallergy
Characteristics = may be itch, may not be
Causes = NSAIDs, abx, diuretics, retinoids, sulfonylureas, phenothiazines antipsychotics and others
The photosensitising properties of these drugs may have clinical usefulness
What are the two types of drug induced photosensitivity?
Photo-toxic = look sunburn-type redness
Photo-allergic = similar to allergic contact dermatitis w/ dry bumpy or blistering rash
What is toxic epidermal necrolysis (TEN) and Steven Johnsons Syndrome (SJS) drug eruption? (what is? when occur? What meds cause? characteristics?)
Believed to be the variant of same conditions, rare, acute, serious, potentially fatal
- start at trunk and spread to face and limbs
Characteristics = sheet-like skin and mucosal loss, px will be ill, anxious, in pain
- prodromal illness for several days (flu-like) before direct onset = fever, sore throat, runny nose, cough, sore eyes, conjunctivitis, aches and pains - abrupt onset of tender, red skin rash or blisters that merge and form detaches skin sheets
Mucosal involvement = eyes, lips, mouth, pharynx, genital area, resp tract, GIT
Cause = abx most common, allopurinol, NSAIDs, nevirapine, paracetamol, anticonvulsants
How are photosensitivity drug eruptions treated?
Stop suspected drug (if possible) = if not, advise on strict sun protection strategies
Consider changing time of drug administration
Moderate-potent topical corticosteroids +/- wet compress
Emollients for sx relief
Analgesia (NSAIDs may reduce severity if given <48 hrs for phototoxic reactions
How is TENS/SJS treated?
Immediate referral to hospital, identify and stop offending agent
Re-epithelialisation can take several weeks, may take months for signs and sx to settle
Long term problems = skin scarring, pigment changes, joint contractures, lung disease, eye problems (blindness)
What are the main causes of death in SJS/TENS?
dehydration, infection, septicaemia, GI perforation, acute resp distress, shock, organ failure, clotting disorders
