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RB Y2 Dermatology > Drug Reactions > Flashcards

Drug Reactions Flashcards

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Dermatology Board Prep flashcards
1
Q

name risk factors for drug eruptions

A
  • young adults > infants/elderly
  • female
  • concomitant disease eg viral infections, CF
  • immune status
  • drugs
    • hapten forming
    • high molecular weight
    • beta lactam
    • NSAIDs
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2
Q

hapten

A
  • molecule that when bound to carrier molecule can elicit an immune response
  • eg urushiol, the toxin found in poison ivy
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3
Q

which drugs cause gingival hyperplasia

A

calcium channel blockers

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4
Q

drug manifestations of co-trixomazole

A
  • erythema nodosum, erythema multiforme, Stevens-Johnsons syndrome
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5
Q

causes of a maculopapular or exanthematous rash

A
  • penicillin, cephalosporins, sulphonamide, anti-epileptics (carbamazepine)
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6
Q

Maculopapular or Exanthematous rash

A
  • the most common type
  • occurs 4-12 days after drug
  • type IV hypersensitivity reaction
  • Usually mild and self-limiting, but can progress to severe life-threatening reaction
  • Presenting with generalised erythematous macule and papules with/out fever and eosinophilia
    • Wide spread symmetrical rash
    • Pruritus
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7
Q

name 6 indicators of a potenitally more severe reaction

A
  • Involvement of mucous membranes and face (oedema and erythema)
  • Widespread confluent erythema
  • Fever (>38.5)
  • Blisters, purpura and necrosis
  • SOB, wheezing
  • Lymphadenopathy and arthralgia
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8
Q

what does a maculopapular/exanthematous rash resemble

A

measles

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9
Q

what is a true allergy due to

A

immunological mechanism

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10
Q

urticarial rash

A
  • usually due to true allergy or pseudoallergy
  • characterise by wheals or angioedema
  • associated with anaphylaxis
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11
Q

how quickly does an uritcarial rash come on

A

within the hour

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12
Q

wheals

A
  • A wheal is a superficial skin-coloured or pale skin swelling, usually surrounded by erythema. Usually very itchy, may have a burning sensation
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13
Q

angioedema

A
  • Angioedema is a deeper swelling within the skin or mucous membranes
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14
Q

true allergy

A

IgE mediated hypersensitivity reaction after re challenge with drug causes an urticarial reaction

  • pencillin - 0.05%
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15
Q

pseudoallergy

A
  • direct release of infalmmatory medaitors from mast cells on first exposure causes a urticarial reaction
  • eg NSAIDs, opiates cause mast cell degranulation
  • eg Penicillin and Cephalosporins trigger IgE responses
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16
Q

which drugs can cause acne

A

steroids, androgens

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17
Q

drugs inducing bullous pemphigoid

A
  • ACE inhibitors, penicillin, furosemide
18
Q

fixed drug eruption

A
  • lesions occur in the same area every time a particular drug is taken - the number of sites involved may increase
  • well demarcated red painful round/ovoid plaques
  • may resolve with persistent pigmentation once the drug is stopped
19
Q

which drugs can cause a fixed drug eruption

A

paracetamol, tetracycline, sulfonamide and aspirin

20
Q

SJS and TEN

A
  • SJS and TEN are believed to be variants of the same condition, distinct from erythema multiforme
  • Rare, acute, serious and potentially fatal skin reaction in which there is sheet-like skin and mucosal loss
  • Anyone on medication can develop it unpredictably.
21
Q

which drugs are known to cause SJS/TEN

A
  • NSAIDs, steroids, methotrexate, allopurinol, sulphonamides, co-trimoxazole, anti-convulsants and penicillins
22
Q

what is the most common infectious cause of SJS/TEN

A

Mycoplasma pneumoniae

23
Q

clinical features of SJS/TEN

A
  • prodromal illness resembling URT infection
  • Abrupt onset of tender/painful skin rash that spreads rapidly. Blisters merge to form sheets of skin detachment
  • Nikolsky’s sign positive
  • eyes: symbblepharon, conjunctivitis, anterior uveitis, corneal ulcers etc
24
Q

side effects of phenytoin

A

an anti convulsant

  • An antifolate drugs that can cause folate deficiency resulting in macrocytic anaemia. A symptom of this is tiredness
  • Duputyren’s contracture
  • Gingival hypertrophy
  • Morbilliform rash/acne
  • SJS/TEN
25
Q

define adverse drug reaction

A

Defined as any undesirable reaction, whether expected, predictable or not that results in a detriment to the wellbeing of the patient in any way, whether symptomatic, detectable or not, in the absence of another biologically plausible explanation that can be proven.

26
Q

type A drug reactions

A

A: Augmented pharmacological effects – dose dependent and predictable

27
Q

diuretics cauing dehydration

A

type A reaction

28
Q

ACEi/ARB causing d and v

A

type A reaction

29
Q

name two causes of post renal failure

A
  • Methysergide – used for migraine and cluster headaches. Causes retroperitoneal fibrosis
  • Chemotherapy – used for acute leukaemias

type A reactions

30
Q

type B reactions

A

B: Bizarre effects (or idiosyncratic) – dose independent and unpredictable

31
Q

give 3 examples of type B reactions

A
  • Drug rashes
  • Chloramphenicol causes bone marrow aplasia
  • Halothane (general anaesthetic) causes hepatic necrosis
32
Q

type C reactions

A

chronic - due to prolonged therapy

33
Q

give 3 examples of type C reactions

A
  • Steroid therapy – Cushing’s disease
  • Beta blockers can lead to diabetes through decrease in peripheral blood flow and altered insulin sensitivity
    • This is why they ae not used much in young people with hypertension
  • NSAIDs can lead to hypertension – see above
34
Q

how can type C reactions be prevented

A
  • emphasise the importance of monitoring - can be anticipated
  • the patient must be warned before starting therapy
35
Q

type D drug reaction

A

delayed - remote from treatment, often years after stopping

36
Q

type D reactions - 2 examples

A
  • Secondary malignancies post chemotherapy
  • Craniofacial abnormalities in the children of women taking isotretinoin
37
Q

type E reactions

A

end of treatment effect - can be due to abrupt withdrawal/rebound effects

38
Q

steroid withdrawal can cause

A

Addisonian crisis - type E reaction

39
Q

beta blocker withdrawal can cause

A

unstable angina in a pt with angina - type E

40
Q

drug food interactions

A
41
Q

what is a true penicillin allergy due to

A
  • Allergy is due to a degradation product of the beta-lactams, true anaphylactic reactions only occur <0.05%
  • Aztreonam is safe in penicillin type 1 allergy, it is a beta-lactam that is active against Gram negative bacteria.

RB Y2 Dermatology (22 decks)

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