22 - Drugs & Allergy Flashcards
1
Q
What is considered a serious allergic reaction to penicillin? Was is not a serious reaction?
A
- Serious = swollen lips, tongue, shortness of breath
- Not serious = N/V, GI upset
2
Q
Define macule
A
Flat area of altered colour less than 1 cm
3
Q
Define patch
A
Large macule over 1 cm
4
Q
Define papule
A
Elevated skin lesion less than 1 cm
5
Q
Define nodule
A
Elevated skin lesion greater than 1 cm
6
Q
Define plaque
A
Elevated flat topped, irregular border less than 1 cm
7
Q
Define vesicles
A
Clear fluid filled blisters less than 0.5 cm
8
Q
Define bulla
A
Large fluid filled blisters greater than 0.5 cm
9
Q
Define pustule
A
Vesicle filled w/ purulent exudate
10
Q
Define wheal
A
Accumulation of dermal fluid
11
Q
What are the different classifications of allergic reactions?
A
- Immediate (0-1 h); type 1 = severe or possibly non-immunologic
- Accelerated (2-72 h); may be any type
- Late (over 72 h); may be any type, but rarely type 1
12
Q
What is a non-immunologic reaction?
A
- Looks like an allergic reaction, but actually due to toxicity
- Ex: red man’s syndrome from vancomycin; tx is to slow down vancomycin infusion
13
Q
What are the types of allergic reactions?
A
- Type 1 or anaphylaxis (IgE mediated)
- Type 2 or cytotoxic (IgG or IgM mediated)
- Type 3 immune complex or serum sickness
- Type 4 or cutaneous eruptions (T-cell mediated)
14
Q
What are the sx of a type 1 allergic reaction?
A
Urticaria, laryngeal edema, bronchospasm, anaphylaxis
15
Q
What are the sx of a type 2 allergic reaction?
A
- Hemolytic anemia
- Thrombocytopenia
- Granulocytopenia
16
Q
What is the onset time of type 2 allergic reactions?
A
Variable
17
Q
What is the onset time of type 3 allergic reactions?
A
5-21 days after exposure
18
Q
What is the difference between type 2 and type 3 allergic reactions?
A
Same, except type 3 is non-hematologic
19
Q
What are the sx of a type 3 allergic reaction?
A
- Fever
- Arthralgias
- Skin rash
- Lymphadenopathy
20
Q
What is unique about type 4 allergic reactions?
A
Not mediated by antibodies like the other 3
21
Q
What are the subtypes of type 4 allergic reactions? What is an example of each?
A
- Type 4a - contact dermatitis
- Type 4b - DRESS syndrome
- Type 4c - contact dermatitis, maculopapular reactions, bullous drug eruptions, Stevens-Johnson syndrome
- Type 4d - acute generalized exanthematous pustulosis (AGEP)
22
Q
What are the 2 main types of contact dermatitis?
A
- Antigen type (20%) takes several days of exposure **true allergic reaction
- Irritant type (80%) w/in hours of exposure
23
Q
What are the sx of AGEP? What is the onset and duration?
A
- Pustules and fever, but non-infectious
- Onset w/in 3 days
- Resolves in 10 days of stopping drug
24
Q
What is erythema multiforme often associated w/?
A
- Herpes infection or histoplasmosis
- Not associated w/ a drug
25
What are the sx of erythema multiforme?
- Eruption of erythematous, raised patches of skin
- Center of lesion eventually clears and forms "target" appearance in 24-48 h
- Lesions appear on 1 mucosal surface and on hands and feet
- Pruritic and sudden onset
- Rash usually distributed symmetrically over body
26
Is Stevens-Johnson syndrome a form of serum sickness?
No!! SJS involves mucosa surfaces, while serum sickness never does
27
What are the sx of Stevens-Johnson syndrome?
- Similar to erythema multiforme but lesions break out at multiple sites (2 or more mucosal membranes); less than 10% BSA involved
- Lining of mouth, throat, genital region, and eyes
- May not see target lesions
28
Which drugs are associated w/ SJS and TENS?
- Sulfonamides*
- Beta-lactams
- NSAIDs
- Anticonvulsants
29
Can desensitization be used for an SJS or TENS reaction?
No
30
Can SJS or TENS be fatal?
Yes
31
What is the difference between SJS and TENS? When is a reaction considered SJS/TENS overlap?
- SJS involves less than 10% BSA; TENS involves more than 30% BSA
- SJS/TENS overlap is when 10-30% BSA involved
32
What is the typical onset for SJS or TENS?
- 4 days to 3 weeks after first dose of the offending drug
| - We generally consider up to 8 weeks for it still being related to that drug
33
What are the sx of TENS?
- Top layer of skin peeling off in sheets
- Greater than 30% BSA involved
- Begins w/ painful red area that spreads quickly (days)
- Affected area has scaled appearance, blisters may develop
- Spreads to mucous membranes of eyes, mouth, and genitals
34
When is SJS/TENS more common?
- HIV-infected patients
| - Possibly those w/ SLE (lupus)
35
What happens when a px has an SJS or TENS reaction a drug?
Can never use that drug again or associated classes of drugs
36
What does DRESS stand for? What is another name for DRESS?
- Drug rash, eosinophilia, and systemic symptoms
| - Aka drug-induced hypersensitivity syndrome or anticonvulsant hypersensitivity syndrome
37
What is the onset of DRESS syndrome?
4 days to 3 weeks
38
What are the sx of DRESS syndrome?
- May initially appear as simple morbilliform rash, but febrile
- Facial edema and erythema are hallmarks of DRESS
- Rash may become purpuric (purplish discolouration), especially on lower legs
- Mucous membranes not involved
39
What drugs are often associated w/ DRESS syndrome?
- Anticonvulsants (phenobarbital, phenytoin)
- Allopurinol
- NSAIDs
- Sulfonamides
- Dapsone
- Thiazides
40
Can desensitization be used for DRESS syndrome?
No
41
If a drug causes histamine release, is it a true anaphylactic reaction?
No, not IgE mediated
42
What can be detected to determine if a reaction is anaphylactic?
- Mast cell tryptase
- Serum tryptase levels should be drawn 1-4 hours after reaction in order to get a definitive diagnosis (if don't test in this window, levels will be too low)
43
What reactions can occur from penicillin allergies?
- Type 1, 2, 3, or 4
- Rash can be hive-like or urticarial
- Classically an erythematous, maculopapular rash
44
Which penicillins most commonly cause rashes?
Ampicillin, amoxicillin
45
What type of allergic reaction is a maculopapular or morbilliform rash to penicillin? If a px experiences this reaction, can they receive penicillins in the future?
- Not IgE mediated, so not type 1
- Either type 4b or 4c
- Not immediate type
- Can receive penicillins or cephalosporins again
46
What type of allergic reaction is urticaria to penicillin? If a px experiences this reaction, can they receive penicillins in the future?
- IgE mediated, immediate type reaction
| - Never give offending agent again
47
When doing penicillin skin testing, what is tested?
- IgE antibodies for accelerated reactions (2-72 h)
| - Parent compound or secondary metabolite (penicillin or penicillate) for immediate reactions
48
If a px is negative on a penicillin skin test, can they receive penicillin?
Yes, anaphylaxis has never occurred in a skin test negative px
49
Do corticosteroids or antihistamines alter the results of a penicillin skin test?
- Corticosteroids no
| - Antihistamines yes (must stop all drugs w/ antihistamine properties 24 h before test)
50
If a px is positive on a penicillin skin test, can they receive penicillin?
No
51
Can penicillin skin testing predict non-IgE mediated reactions (ex: DRESS, SJS, TENS, cytopenias)?
No, so can have a negative test & still experience a non-IgE mediated reaction
52
If a px is positive on a penicillin skin test, can they receive cephalosporins?
- Yes, but only if alternatives are less desirable
| - Never should receive them if px has a history of anaphylaxis or urticaria
53
What type of reaction is a sulfonamide rash?
Delayed reaction (week 2 of tx)
54
What often accompanies a sulfonamide rash?
- Pruritus and fever
| - Morbilliform eruption
55
What is desensitization? Which reactions can this be done for?
- Temporary induction of drug tolerance through exposing px to very minute quantities of the offending drug (ex: 1/10,000 dilution) and then rapidly increasing concentrations of exposure (ie: doubling dose every 15-20 mins) until full dose is tolerated
- Only lasts as long as the drug is in the body
- Only for type 1 reactions (IgE mediated)
56
What is graded challenge? When is it used?
- Administration of a graduated amount under close supervision
- Used to exclude drug allergy in those who you suspect to be unlikely allergic to the drug
57
What are contraindications to the graded challenge?
- Suspected type 1 reaction (graded challenge could induce anaphylaxis)
- History of blistering dermatitis (ex: SJS/TENS) or severe hypersensitivity reactions (ex: DRESS)
58
What should be done if you can't determine which drug is the culprit of an allergic reaction?
Stop newest medication first, w/ subsequent withdrawal of older agents until rash resolves
59
What is the tx for mild drug allergic reactions?
Treat symptoms w/ topical corticosteroid and systemic antihistamines for pruritus
