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Year 4 - Toxicology > Skin > Flashcards

Skin Flashcards

1
Q

What is the function of skin?

A

-thermal, electrolyte, metabolic and immune regulation

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2
Q

What is on/in the epidermis?

A
  • melanocytes
  • langerhans cells
  • keratinocytes
  • hair follicles, sebaceous and eccrine glands
  • P450 enzymes (degradation, activation)
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3
Q

Describe the dermis

A
  • 90% of the skin
  • supportive function
  • high content of collagen and elastin
  • fibroblasts
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4
Q

Rate of Cutaneous Drug Reactions

A

0-8%

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5
Q

What drugs are most likely to cause cutaneous drug reactions

A

antibiotics (penicillins very common)

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6
Q

What skin reactions can happen?

A
  • Maculopapular rash (morbiliforme): 91%
  • Urticaria (hives): 6%
  • SJS
  • Toxic Epidermal Necrolysis
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7
Q

Two forms of contact dermatitis

A
  • Irritant

- Allergic

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8
Q

Describe presentation of contact dermatitis

A
  • erythema (redness)
  • induration (increase in tissue, can cause a hardened mass, making it thick)
  • scaling
  • vesiculation
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9
Q

Irritant contact dermatitis:

-Intensity of rxn is proportional to the ____ applied

A

dose

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10
Q

Irritant contact dermatitis:

Non-______ mechanism

A

immunologic

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11
Q

Allergic contact dermatitis is what?

A 
a delayed (type 4) hypersensitivity reaction
*have to be previously exposed
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12
Q

Allergic contact dermatitis:

Describe the response

A

within 12 hours of sensitization, peaks at 48-72 hours

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13
Q

How much of contact dermatitis does allergic make up and irritant make up?

A

Irritant: 75%
Allergic: 25%

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14
Q

List some topical medications that can cause allergic contact dermatitis

A
  • bacitracin
  • neomycin
  • polymyxin
  • aminoglycosides
  • sulfonamides
  • benzocaine
  • corticosteroids
  • vitamin E
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15
Q

What is Contact Urticaria?

A
  • Transient, pruritic, oedematous, pink papule or wheals

- Due to histamine release

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16
Q

What type of immune reaction is contact urticaria?

A

type 1 immune reaction (IgE mediated)

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17
Q

What drugs can cause the IgE mediated reaction for contact urticaria?

A
  • bacitracin
  • ASA
  • ampicillin
  • neomycin
  • phenothiazines
  • latex
18
Q

What can cause a non-immunologic contact urticaria ?

A
  • benzocaine
  • capsaicin
  • nicotinic acid esters
  • jellyfish venom
  • no need for previous exposure
    i. e. first time you get stung by jelly fish you get the reaction
19
Q

What is photo toxicology??

A
  • skin is exposed to radiations

- solar radiation most capable of inducing skin changes ranges from 290-700nm

20
Q

What does absorption of light depend upon?

A

chromophores, epidermal thickness and water content

21
Q

What absorbs UV-B?

A
  • melanin
  • amino acids

(290-320nm)

22
Q

What is photosensitivity?

A

abnormal sensitivity to UV and visible light

23
Q

What can cause photosensitivity?

A

Endogenous: lupus or porphyrias

Exogenous: tanning booths, chemicals in cosmetics, drugs

24
Q

Phototoxicity can occur at the ____ exposure

A

first

25
Q

What is most commonly involved in phytotoxicity?

A

UV-A (320-400nm)

26
Q

When do chemicals absorb UV light

A

In a higher energy excited state:

  • oxygen-dependent
  • free radicals (cell death)
  • immunomediators from keratinocytes and WBC
27
Q

What are acute reactions of phytotoxicity?

A
  • red skin
  • blister within minutes to hours (sunburn)
  • desquamation, peeling
28
Q

What are chronic reactions of phytotoxicity?

A
  • hyperpigmentation

- thickening

29
Q

What drugs can cause phytotoxicity?

A
  • amiodarone
  • fluoroquinolones
  • captopril
  • TCAs
  • fluorouracil
  • furosemide
  • nalidixic acid
  • naproxen
  • NSAIDs
  • phenothiazines
  • tetracycline
  • vinblastin
  • warfarin
30
Q

What is photo allergy?

A
  • True Type 4 delayed hypersensitivity reaction

- Requires prior sensitization

31
Q

How does photo allergy occur?

A

UV light is necessary to convert a potential photosensitizing chemical into a happen that binds to a tissue antigen = allergic response at subsequent exposures

32
Q

What drugs cause photo allergy?

A
  • antihistamines
  • barbiturates
  • TCAs
  • diltiazem
  • glyburide
  • griseofulvin
  • NSAIDs
  • PABA
  • phenothiazines
  • procaine
  • quinidine
  • quinine
  • sulfonamides
  • thiazides
33
Q

What is the most common dermatosis induced by systemic drugs?

A

maculopapular eruptions

34
Q

Describe the clinical presentation of maculopapular eruptions

A
  • morbilliform
  • exanthematous
  • rubellaform eruptions - initially appear on truck and pressure areas and spread to entire body - flat or raised erythematous lesions symetrically distributed - few mm size to confluent large areas
  • itchy macules and papules
35
Q

When do maculopapular eruptions occur?

A

within first week of therapy

36
Q

maculopapular eruptions occurs in 3-7% of patients receiving what drugs

A

ampicillin or amoxicillin

37
Q

What are some other drugs that can cause maculopapular eruptions?

A
  • cephalosporins
  • gentamicin
  • gold
  • isoniazid
  • phenylbutazone
  • phenytoin
  • sulfonamides
  • thiazides
38
Q

Clinical presentation of urticaria

A
  • pink or red
  • edematous
  • raised papule and plaques
  • localized vasodilation and small transudations f fluid from small cutaneous blood vessels
  • angioedema (usually noticeable on face and around eyes)
39
Q

What are the mechanisms of urticaria?

A
  • Type 1 hypersensitivity reactions
  • Type 3 immune reactions
  • Direct effects on mast cell (opioids)
  • Inhibition of prostaglandins (ASA, NSAIDS)
40
Q

What drugs can cause urticaria?

A
  • ASA
  • NSAIDs
  • gold
  • heparin
  • opioids
  • penicillins
  • sulfonamides
41
Q

Describe fixed-drug eruptions

A

slide 29

Year 4 - Toxicology (24 decks)

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