Skin Flashcards
What is the function of skin?
-thermal, electrolyte, metabolic and immune regulation
What is on/in the epidermis?
- melanocytes
- langerhans cells
- keratinocytes
- hair follicles, sebaceous and eccrine glands
- P450 enzymes (degradation, activation)
Describe the dermis
- 90% of the skin
- supportive function
- high content of collagen and elastin
- fibroblasts
Rate of Cutaneous Drug Reactions
0-8%
What drugs are most likely to cause cutaneous drug reactions
antibiotics (penicillins very common)
What skin reactions can happen?
- Maculopapular rash (morbiliforme): 91%
- Urticaria (hives): 6%
- SJS
- Toxic Epidermal Necrolysis
Two forms of contact dermatitis
- Irritant
- Allergic
Describe presentation of contact dermatitis
- erythema (redness)
- induration (increase in tissue, can cause a hardened mass, making it thick)
- scaling
- vesiculation
Irritant contact dermatitis:
-Intensity of rxn is proportional to the ____ applied
dose
Irritant contact dermatitis:
Non-______ mechanism
immunologic
Allergic contact dermatitis is what?
a delayed (type 4) hypersensitivity reaction *have to be previously exposed
Allergic contact dermatitis:
Describe the response
within 12 hours of sensitization, peaks at 48-72 hours
How much of contact dermatitis does allergic make up and irritant make up?
Irritant: 75%
Allergic: 25%
List some topical medications that can cause allergic contact dermatitis
- bacitracin
- neomycin
- polymyxin
- aminoglycosides
- sulfonamides
- benzocaine
- corticosteroids
- vitamin E
What is Contact Urticaria?
- Transient, pruritic, oedematous, pink papule or wheals
- Due to histamine release
What type of immune reaction is contact urticaria?
type 1 immune reaction (IgE mediated)
What drugs can cause the IgE mediated reaction for contact urticaria?
- bacitracin
- ASA
- ampicillin
- neomycin
- phenothiazines
- latex
What can cause a non-immunologic contact urticaria ?
- 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
What is photo toxicology??
- skin is exposed to radiations
- solar radiation most capable of inducing skin changes ranges from 290-700nm
What does absorption of light depend upon?
chromophores, epidermal thickness and water content
What absorbs UV-B?
- melanin
- amino acids
(290-320nm)
What is photosensitivity?
abnormal sensitivity to UV and visible light
What can cause photosensitivity?
Endogenous: lupus or porphyrias
Exogenous: tanning booths, chemicals in cosmetics, drugs
Phototoxicity can occur at the ____ exposure
first
What is most commonly involved in phytotoxicity?
UV-A (320-400nm)
When do chemicals absorb UV light
In a higher energy excited state:
- oxygen-dependent
- free radicals (cell death)
- immunomediators from keratinocytes and WBC
What are acute reactions of phytotoxicity?
- red skin
- blister within minutes to hours (sunburn)
- desquamation, peeling
What are chronic reactions of phytotoxicity?
- hyperpigmentation
- thickening
What drugs can cause phytotoxicity?
- amiodarone
- fluoroquinolones
- captopril
- TCAs
- fluorouracil
- furosemide
- nalidixic acid
- naproxen
- NSAIDs
- phenothiazines
- tetracycline
- vinblastin
- warfarin
What is photo allergy?
- True Type 4 delayed hypersensitivity reaction
- Requires prior sensitization
How does photo allergy occur?
UV light is necessary to convert a potential photosensitizing chemical into a happen that binds to a tissue antigen = allergic response at subsequent exposures
What drugs cause photo allergy?
- antihistamines
- barbiturates
- TCAs
- diltiazem
- glyburide
- griseofulvin
- NSAIDs
- PABA
- phenothiazines
- procaine
- quinidine
- quinine
- sulfonamides
- thiazides
What is the most common dermatosis induced by systemic drugs?
maculopapular eruptions
Describe the clinical presentation of maculopapular eruptions
- 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
When do maculopapular eruptions occur?
within first week of therapy
maculopapular eruptions occurs in 3-7% of patients receiving what drugs
ampicillin or amoxicillin
What are some other drugs that can cause maculopapular eruptions?
- cephalosporins
- gentamicin
- gold
- isoniazid
- phenylbutazone
- phenytoin
- sulfonamides
- thiazides
Clinical presentation of urticaria
- 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)
What are the mechanisms of urticaria?
- Type 1 hypersensitivity reactions
- Type 3 immune reactions
- Direct effects on mast cell (opioids)
- Inhibition of prostaglandins (ASA, NSAIDS)
What drugs can cause urticaria?
- ASA
- NSAIDs
- gold
- heparin
- opioids
- penicillins
- sulfonamides
Describe fixed-drug eruptions
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