Drug Reactions Flashcards
What is an idiosyncratic reaction?
What is an example of this?
Not explained by pharmacologic properties of the drug
Infectious mononucleosis and penicillin
Which population is at increased risk of developing drug-induced lupus in response to procainamide or hydralazine?
Slow acetylators of N-acetyltransferase
HLA DR4 haplotype + C4 null allele
What is a Jarisch-Herxheimer phenomenon?
Presence of a fever, arthralgias and tender lymphadenopathy with transient macular or urticarial eruptions
Seen with treponema pallidum with initiation of treatment
List an example of a hypersensitivity reaction for each type
- Acute (IgE mediated)
- Urticaria
- Angioedema
- Anaphylaxis
- Cytotoxic (IgG-mediated)
- Blood transfusion reaction
- Immune-complex mediated
- HSP
- Serum sickness
- Delayed (cell-mediated)
- Contacter dermatitis
- Photoallergic reactions
What is the most common type of drug eruption?
What is the typical onset of symptoms?
Morbilliform drug eruption
Starts centrally and moves peripherally
Difficult to determine if drug or bug
1-2 weeks after exposure (1-3 days on reexposure)
What are the most common drug culprits of the morbilliform eruption?
What is the recommended management?
- Penicillins
- Cephalosporins
- Sulfonamides
- Allopurinol
- Anti-convulsants
- NSAIDs
Management
- Identify and discontinue the causative drug
- Treat symptomatically
- Potent topical steroids
- Oil-based emollients with menthol
- Emollient baths
Name this dermatological diagnosis
Where is it commonly located?
What is the common presentation?
Fixed drug eruption
Acral, lips, genitalia
Plaque with hyperpigmentation at the centre
How should you approach a suspected drug reaction?
Complete a drug calendar (usually 4-28 days prior to exposure; up to 8wks for anticonvulsants)
Name this dermatologic diagnosis
Erythrodysasthesia
Name this dermatologic diagnosis
Monomorphous pustular eruption 2˚ steroid-induced acne
List 5 red flag features of a severe drug reaction
What investigations are recommended?
- Fever, dyspnea, hypotension
- Confluent erythema
- Blisters
- +Nikolsky sign
- Mucous membrane involvement
- Angioedema/Tongue swelling
- Palpable purpura
- Skin necrosis
- Lymphadenopathy
Investigations
- CBC
- Renal function
- Liver function
- Antihistone antibodies (drug-induced SLE)
- Anti-Ro/SS-A antibodies (drug-induced SCLE)
- Urinalysis
- Skin biopsy
- Patch test - AGEP
- Lymphocyte transformation
Name this dermatologic diagnosis
What are the associated features?
Acute Generalized Exanthematous Pustulosis (AGEP)
- Fever > 38.5˚C
- Rapid evolution (over hours) of sterile, nonfollicular pustules on erythematous swollen skin with accentuation in body folds
- Facial edema
- Leukocytosis + neutrophilia
- onset < 3 days after 1st dose of an antibiotic (slower onset with other drugs)
Name this dermatological diagnosis
What are the typical features?
Drug Rash with Eosinophilia and Systemic Symptoms (DRESS)
7 = typical DRESS
- Maculopapular rash >3 weeks after drug initiation
- Clinical symptoms continuing >2 weeks after stopping therapy
- Fever > 38˚ C
- Liver abnormalities (ALT >100 IU/L) or other organ involvement (kidney, muscle, lung, heart, pancreas)
- Hematological abnormalities
- Leukocytosis (>11)
- Atypical lymphocytes
- Eosinophilia (>700)
- Thrombocytopenia
- Lymphadenopathy
- HHV-6 reactivaation
What are the initial sites of involvement for SJS/TEN?
When is maximal involvement?
What typically do patients experience before skin signs?
What is the mortality for SJS? TEN?
Upper torso, proximal limbs, face
Day 5-7
Malaise, fever, URTI symptoms with ocular inflammation
<10%; 30%
What is the body surface area amounts for epidermal detachment:
SJS
SJS/TEN
TEN
<10%
10-30%
>30%
