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Year 4 - Toxicology > 22 - Skin > Flashcards

22 - Skin Flashcards

1
Q

Which drugs are most likely to produce skin reactions?

A

Antibiotics

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2
Q

What are the most common cutaneous drug reactions?

A
  • Maculopapular rash (morbilliform) = 91%
  • Urticaria (hives) = 6%
  • SJS, TENS (toxic epidermal necrolysis)
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3
Q

What determines intensity of irritant contact dermatitis?

A

Dose applied

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4
Q

Does irritant contact dermatitis have an

immunlogic mechanism?

A

No

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5
Q

Sx of irritant contact dermatitis

A
  • Eczematous
  • Pink to red patches or plaques
  • Edema in epidermis (blisters)
  • Itching
  • Lichenification (epidermal thickening)
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6
Q

What type of reaction is allergic contact dermatitis?

A

Delayed (type 4) hypersensitivity reaction

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7
Q

Common drugs that can cause allergic contact dermatitis?

A
  • Bacitracin
  • Neomycin
  • Polymyxin
  • Aminoglycosides
  • Sulfonamides
  • Benzocaine
  • Corticosteroids
  • Vitamin E
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8
Q

What type of reaction is contact urticaria?

A

Type 1 immune reaction (IgE mediated)

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9
Q

Common drugs that can cause contact urticaria?

A
  • Bacitracin
  • ASA
  • Ampicillin
  • Neomycin
  • Phenothiazines
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10
Q

What is photosensitivity?

A
  • Abnormal sensitivity to UV and visible light due to endogenous or exogenous factors
  • Can be phototoxicity or photoallergy
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11
Q

Describe phototoxicity

A
  • Can occur at first exposure

- Systemic or topical administration of medications

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12
Q

Characteristics of acute phototoxicity reactions

A
  • Red skin, blisters w/in minutes to hours after UV light exposure (sunburn)
  • Desquamation, peeling
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13
Q

Characteristics of chronic phototoxicity reactions

A
  • Hyperpigmentation

- Thickening

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14
Q

Drugs that can cause phototoxicity

A
  • Amiodarone
  • Fluoroquinolones
  • Captopril
  • TCAs
  • Fluorouracil
  • Furosemide
  • Naproxen, NSAIDs
  • Phenothiazines
  • Tetracycline
  • Warfarin
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15
Q

What type of reaction is photoallergy?

A
  • True type 4 delayed hypersensitivity reaction

- Requires prior sensitization

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16
Q

Describe photoallergy

A
  • Topical meds (photocontact dermatitis) or systemic meds (systemic photoallergy)
  • UV light necessary to convert a potential photosensitizing chemical into a hapten that binds to a tissue Ag => allergic response at subsequent exposures
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17
Q

Drugs causing photoallergy

A
  • Antihistamines
  • Barbiturates
  • TCAs
  • Diltiazem
  • Glyburide
  • NSAIDs
  • Phenothiazines
  • Quinidine, quinine
  • Sulfonamides
  • Thiazides
18
Q

_____ is the most common dermatosis induced by systemic drugs

A

Maculopapular eruptions

19
Q

Clinical presentation of maculopapular eruptions

A
  • Morbilliform, exanthematous, rubellaform eruptions
  • Initially appear on trunk and pressure areas and spread to entire body
  • Flat or raised erythematous lesions, symmetrically distributed
  • Few mm size to confluent large areas
  • Pruritic macules and papules
20
Q

When do maculopapular eruptions usually appear?

A

Within first week of therapy

21
Q

Drugs that can cause maculopapular eruptions?

A
  • Ampicillin, amoxicillin
  • Cephalosporins
  • Gentamicin
  • Isoniazid
  • Phenytoin
  • Sulfonamides
  • Thiazides
22
Q

Clinical presentation of urticaria

A
  • Pink or red, edematous, raised papules and plaques
  • Localized vasodilation and transudation of fluid from small cutaneous blood vessels
  • Angioedema
23
Q

Mechanisms of urticaria

A
  • Type 1 hypersensitivity reactions
  • Type 3 immune reactions
  • Direct effects on mast cells (opioids)
  • Inhibition of prostaglandins (ASA, NSAIDs)
24
Q

Drugs associated w/ urticaria

A
  • ASA, NSAIDs
  • Gold
  • Heparin
  • Opioids
  • Penicillins, sulfonamides
25
Q

Describe fixed-drug eruptions

A
  • Lesions occur at same sites on repeated administration of the drug
  • Red, oval or circular patch w/ central pigmentation and/or blistering, asymptomatic or w/ burning
  • Face, hands, feet, mouth
  • Healing occurs 7-10 days following discontinuation
26
Q

Drugs causing fixed-drug eruptions

A
  • Acetaminophen
  • ASA
  • Allopurinol
  • Barbiturates
  • Penicillins
  • Sulfonamides
  • Tetracyclines
27
Q

What type of reaction is erythema multiforme?

A

Type 3 immune reaction

28
Q

Describe erythema multiforme?

A
  • Erythematous maculae that becomes edematous and popular over time
  • Concentric rings of different colours (red from vasodilation, purple from erythrocyte extravasation, white from edema, black from necrosis)
  • Common sites = face, hands, libs, mucous membranes
29
Q

Describe Stevens-Johnson syndrome

A
  • Severe variant of erythema multiforme
  • Extensive mucosal and conjunctival edema, erosions
  • High fever, myalgia, vomiting, diarrhea, and arthralgias
  • Skin lesions can be severe w/ areas of denudation
30
Q

Complications of Stevens-Johnson syndrome

A
  • Keratitis
  • Conjunctival scarring
  • Blindness
  • Pneumonia
  • Dehydration
  • Esophagitis
31
Q

Drugs causing SJS

A
  • Barbiturates
  • Carbamazepine
  • Ibuprofen
  • Penicillins
  • Phenylbutazone
  • Quinine
  • Salicylates
  • Sulfonamides
  • Sulfonylureas
  • Thiazides
32
Q

Describe toxic epidermal necrolysis (TEN)

A
  • Life-threatening (second only to anaphylaxis) -> 30-50% mortality rates (when diffuse sloughing present)
  • Rare; medications involved in 80-95% of cases
33
Q

Drugs causing TEN

A
  • Allopurinol
  • Barbiturates
  • Chloramphenicol
  • Ibuprofen
  • Indomethacin
  • Penicillins
  • Quinine
  • Sulfonamides
34
Q

Clinical manifestation of TEN

A
  • Prodromal state of malaise, sore throat, headache, myalgia, fever, arthralgia, N/V/D, chest pain, cough
  • Acute onset of cutaneous manifestations w/in hours or days
  • Macular lesion w/ burning sensation that enlarges over the body, may form large flaccid bullae w/in erythema
  • Detachment of epidermis (necrosis)
  • Common sites = palms, soles, mouth, throat, nose, trachea, eyelids, conjunctiva, cornea
35
Q

Complications of TEN

A
  • Similar to second degree burns
  • Fluid and electrolyte imbalances
  • Septicemia
  • Pneumonia
  • Hepatocellular damage
  • GI ulceration
  • Nephritis
  • Myocardial damage
36
Q

Describe erythema nodosum

A

Inflammatory reaction of subcutaneous fat (nodules)

37
Q

Drugs causing erythema nodosum

A
  • Amiodarone
  • Bromides
  • Penicillins
  • Salicylates
  • Sulfones
  • Tetracyclines
38
Q

Drugs causing drug-induced lupus erythematous

A
  • Barbiturates
  • Ibuprofen
  • Methyldopa
  • Penicillamine
  • Phenothiazines
  • Phenytoin
  • Procainamide
  • Quinidine
  • Trimethoprim
39
Q

What is purpura?

A

Bleeding into the skin

40
Q

Causes of purpura

A
  • Drugs that interfere w/ platelet aggregation (valproic acid, ASA)
  • Drugs that interfere w/ coagulation (warfarin, heparin)
  • Cytotoxic drugs
  • Direct endothelial damage (bleomycin)
41
Q

What is hyperpigmentation?

A

Deposit of melanin in dermis or stimulation of melanin production

42
Q

Which drugs can cause hyperpigmentation?

A
  • Amiodarone
  • Chloroquine
  • Minocycline
  • Heavy metals
  • Tetracyclines
  • Oral contraceptives

Year 4 - Toxicology (22 decks)

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