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Clinical - Winter > 22 - Drugs & Allergy > Flashcards

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

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2
Q

Define macule

A

Flat area of altered colour less than 1 cm

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3
Q

Define patch

A

Large macule over 1 cm

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4
Q

Define papule

A

Elevated skin lesion less than 1 cm

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5
Q

Define nodule

A

Elevated skin lesion greater than 1 cm

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6
Q

Define plaque

A

Elevated flat topped, irregular border less than 1 cm

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7
Q

Define vesicles

A

Clear fluid filled blisters less than 0.5 cm

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8
Q

Define bulla

A

Large fluid filled blisters greater than 0.5 cm

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9
Q

Define pustule

A

Vesicle filled w/ purulent exudate

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10
Q

Define wheal

A

Accumulation of dermal fluid

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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
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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
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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)
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14
Q

What are the sx of a type 1 allergic reaction?

A

Urticaria, laryngeal edema, bronchospasm, anaphylaxis

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15
Q

What are the sx of a type 2 allergic reaction?

A
  • Hemolytic anemia
  • Thrombocytopenia
  • Granulocytopenia
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16
Q

What is the onset time of type 2 allergic reactions?

A

Variable

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17
Q

What is the onset time of type 3 allergic reactions?

A

5-21 days after exposure

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18
Q

What is the difference between type 2 and type 3 allergic reactions?

A

Same, except type 3 is non-hematologic

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19
Q

What are the sx of a type 3 allergic reaction?

A
  • Fever
  • Arthralgias
  • Skin rash
  • Lymphadenopathy
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20
Q

What is unique about type 4 allergic reactions?

A

Not mediated by antibodies like the other 3

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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)
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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
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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
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24
Q

What is erythema multiforme often associated w/?

A
  • Herpes infection or histoplasmosis

- Not associated w/ a drug

25
Q

What are the sx of erythema multiforme?

A
  • 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
Q

Is Stevens-Johnson syndrome a form of serum sickness?

A

No!! SJS involves mucosa surfaces, while serum sickness never does

27
Q

What are the sx of Stevens-Johnson syndrome?

A
  • 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
Q

Which drugs are associated w/ SJS and TENS?

A
  • Sulfonamides*
  • Beta-lactams
  • NSAIDs
  • Anticonvulsants
29
Q

Can desensitization be used for an SJS or TENS reaction?

A

No

30
Q

Can SJS or TENS be fatal?

A

Yes

31
Q

What is the difference between SJS and TENS? When is a reaction considered SJS/TENS overlap?

A
  • SJS involves less than 10% BSA; TENS involves more than 30% BSA
  • SJS/TENS overlap is when 10-30% BSA involved
32
Q

What is the typical onset for SJS or TENS?

A
  • 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
Q

What are the sx of TENS?

A
  • 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
Q

When is SJS/TENS more common?

A
  • HIV-infected patients

- Possibly those w/ SLE (lupus)

35
Q

What happens when a px has an SJS or TENS reaction a drug?

A

Can never use that drug again or associated classes of drugs

36
Q

What does DRESS stand for? What is another name for DRESS?

A
  • Drug rash, eosinophilia, and systemic symptoms

- Aka drug-induced hypersensitivity syndrome or anticonvulsant hypersensitivity syndrome

37
Q

What is the onset of DRESS syndrome?

A

4 days to 3 weeks

38
Q

What are the sx of DRESS syndrome?

A
  • 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
Q

What drugs are often associated w/ DRESS syndrome?

A
  • Anticonvulsants (phenobarbital, phenytoin)
  • Allopurinol
  • NSAIDs
  • Sulfonamides
  • Dapsone
  • Thiazides
40
Q

Can desensitization be used for DRESS syndrome?

A

No

41
Q

If a drug causes histamine release, is it a true anaphylactic reaction?

A

No, not IgE mediated

42
Q

What can be detected to determine if a reaction is anaphylactic?

A
  • 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
Q

What reactions can occur from penicillin allergies?

A
  • Type 1, 2, 3, or 4
  • Rash can be hive-like or urticarial
  • Classically an erythematous, maculopapular rash
44
Q

Which penicillins most commonly cause rashes?

A

Ampicillin, amoxicillin

45
Q

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?

A
  • Not IgE mediated, so not type 1
  • Either type 4b or 4c
  • Not immediate type
  • Can receive penicillins or cephalosporins again
46
Q

What type of allergic reaction is urticaria to penicillin? If a px experiences this reaction, can they receive penicillins in the future?

A
  • IgE mediated, immediate type reaction

- Never give offending agent again

47
Q

When doing penicillin skin testing, what is tested?

A
  • IgE antibodies for accelerated reactions (2-72 h)

- Parent compound or secondary metabolite (penicillin or penicillate) for immediate reactions

48
Q

If a px is negative on a penicillin skin test, can they receive penicillin?

A

Yes, anaphylaxis has never occurred in a skin test negative px

49
Q

Do corticosteroids or antihistamines alter the results of a penicillin skin test?

A
  • Corticosteroids no

- Antihistamines yes (must stop all drugs w/ antihistamine properties 24 h before test)

50
Q

If a px is positive on a penicillin skin test, can they receive penicillin?

A

No

51
Q

Can penicillin skin testing predict non-IgE mediated reactions (ex: DRESS, SJS, TENS, cytopenias)?

A

No, so can have a negative test & still experience a non-IgE mediated reaction

52
Q

If a px is positive on a penicillin skin test, can they receive cephalosporins?

A
  • Yes, but only if alternatives are less desirable

- Never should receive them if px has a history of anaphylaxis or urticaria

53
Q

What type of reaction is a sulfonamide rash?

A

Delayed reaction (week 2 of tx)

54
Q

What often accompanies a sulfonamide rash?

A
  • Pruritus and fever

- Morbilliform eruption

55
Q

What is desensitization? Which reactions can this be done for?

A
  • 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
Q

What is graded challenge? When is it used?

A
  • 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
Q

What are contraindications to the graded challenge?

A
  • Suspected type 1 reaction (graded challenge could induce anaphylaxis)
  • History of blistering dermatitis (ex: SJS/TENS) or severe hypersensitivity reactions (ex: DRESS)
58
Q

What should be done if you can’t determine which drug is the culprit of an allergic reaction?

A

Stop newest medication first, w/ subsequent withdrawal of older agents until rash resolves

59
Q

What is the tx for mild drug allergic reactions?

A

Treat symptoms w/ topical corticosteroid and systemic antihistamines for pruritus

Clinical - Winter (24 decks)

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