Drug Eruptions Flashcards

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1
Q

What are examples of a cutaneous manifestation of type 1 hypersensitivity?

A

Urticaria
Eczema
Psoriasis

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2
Q

What are examples of a cutaneous manifestation of type 2 hypersensitivity?

A

Pemphigus and pemphigoid

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3
Q

What are examples of a cutaneous manifestation of type 3 hypersensitivity?

A

Purpura, rash

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4
Q

What are examples of a cutaneous manifestation of type 4 hypersensitivity?

A

Erythema, rash

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5
Q

Is a drug-induced type 4 hypersensitivity reaction dose-dependent (and what does that mean)?

A

No - it can’t be helped by taking a smaller dose of the drug causing the reaction

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6
Q

What are the different types of clinical presentation of a drug-induced reaction?

A
Exanthemous/maculopapular
Urticarial
Papulo-squamous/pustular/bullous
Pigmentation
Itch/pain
Photosensitivity
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7
Q

When should you consider a drug-induced reaction?

A

Any patient taking medication who suddenly develops a symmetrical skin eruption
Usually resolves when the drug is withdrawn

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8
Q

What are patient risk factors for a drug-induced reaction?

A

Age - more common in young adults than infants and elderly
Gender - females > males
Concomitant disease (viral infections e.g. HIV, cystic fibrosis)
Immune status
Previous drug reaction or positive skin test

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9
Q

What are drug risk factors for a drug-induced reaction?

A

Drug biochemistry - beta-lactam compounds, NSAIDs, high molecular weight
Route of administration
Dose
Kinetics/half-life

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10
Q

What factors should be considered when trying to identify which drug is causing a reaction in a patient on multiple drugs?

A

Which drug is known to be most likely to cause an eruption
Time interval between exposure and development of skin reaction
History of previous exposure to the same drug

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11
Q

What is the most common type of drug reaction?

A

Exanthematous

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12
Q

What are exanethmatous drug reactions?

A

Type 4 hypersensitivity - delayed
Mild and self-limiting
Idiosyncratic

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13
Q

How do exanthematous drug reactions present?

A

Widespread symmetrically distributed rash
Pruritis is common
Mild fever is common
Mucus membranes usually spared

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14
Q

When are exanthematous drug reactions usually onset?

A

4-21 days after first taking drug

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15
Q

What are indicators pf a potentially severe and life-threatening exanthematous drug reaction?

A
Involvement of mucous membranes and face
Widespread confluent erythema
Fever
Skin pain
Blisters, purpura, necrosis
Lymphadenopathy, arthralgia
Shortness of breath, wheezing
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16
Q

What are some drugs associated with exanthematous drug reactions?

A
Penicillins
NSAIDs
Sulphonamides
Erythromycin
Allopurinol
17
Q

What are urticarial drug reactions?

A

Usually type 1 hypersensitivity reactions - allergy

Produce urticaria, may be associated with angioedema or anaphylaxis

18
Q

What are the two ways drugs can cause an urticarial reaction?

A

After re-challenge with drug

Direct release of inflammatory mediators from mast cells on first exposure

19
Q

What are examples of drugs that produce an urticarial reaction after re-challenge with drug?

A

Beta-lactams

Carbamazepine

20
Q

What are examples of drugs that produce an urticarial reaction due to direct release of inflammatory mediators from mast cells on first exposure

A
Aspirin
Opiates
NSAIDs
Muscle relaxants
Vancomycin
Quinolones
21
Q

What is the difference between the presentations of acneiform drug reactions and acne?

A

In drug reactions the skin is not shiny - clue that it is not acne

22
Q

What are examples of drugs that cause acneiform drug reactions?

A

Glucocorticosteroids

Androgens

23
Q

What is acute generalised exanthematous pustulosis, and what drugs can it be caused by?

A
Rare pustular drug eruption
Can look like pustular psoriasis
Antibiotics
Calcium channel blockers
Anti-malarials
24
Q

What drugs can cause drug-induced bullous pemphigoid?

A

ACE-inhibitors
Penicillin
Furosemide

25
Q

What is the presentation of fixed drug eruptions?

A

Well demarcated round/ovoid plaques
Red, painful
Hands, genitalia, lips
Resolves but leaves persistence pigmentation when drug is stopped
Can also present as eczematous lesions, papule, vesicles or urticaria

26
Q

What are drugs associated with fixed drug eruptions?

A

Tetracycline, doxycycline
Paracetamol
NSIADs
Carbamazepine

27
Q

What are the different severe cutaneous adverse drug reactions?

A

Stevens-Johnson syndrome
Toxic epidermal necrolysis
Drug reaction with eosinophilia and systemic symptoms
Acute generalised exanthemous pustulosis

28
Q

How do acute phototoxic drug reactions present?

A

Skin toxicity - photosensitivity
Systemic toxicity
Photodegredation

29
Q

How do chronic phototoxic drug reactions present?

A

Pigmentation
Photoageing
Photocarcinogenesis

30
Q

What is a phototoxic drug reaction?

A

A non-immunological skin reaction arising an individual exposed to enough photo reactive drug and light of the appropriate wavelength

31
Q

What can increased sensitivity to sunlight be caused by?

A

Drugs
Immunosuppression
Lupus

32
Q

What are some patterns of skin phototoxicity?

A

Immediate prickling with delayed erythema and pigmentation
Exaggerated sunburn
Exposed telangiectasia
Delayed 3-5 days erythema and pigmentation
Increased skin fragility

33
Q

What are some drugs associated with phototoxic drug reactions?

A
Antibiotica
Thiazodes
NSAIDs
Amiodarone
Antifungals
Immunosuppressants
34
Q

What are important things to know in a history of a drug reaction?

A

Detailed description of reaction
Timing of onset of symptoms in relation to drug administration
Previous exposure to drug
When did the drug start, when was it stopped and did stopping affect symptoms
Photograph of reaction
Why was the drug being taken, underlying illness?
Comprehensive drug history

35
Q

What investigations should be done for a drug reaction?

A

History and examination usually sufficient
Phototesting for suspected phototoxic reactions
Biopsy
Patch and photo-patch tests
Skin prick test for specific drugs

36
Q

What is the management for a drug reaction?

A
Discontinue drug if possible
Use alternative
Topical corticosteroids
Anti-histamine if type 1 or symptoms of itch
Allergy bracelets