cutaneous drug eruptions

Question 1

what are they?

Answer 1

side effects of skin - account for 30% of drug reactions

Question 2

what is the issue with them?

Answer 2

they mimic other skin diseases and are becoming more common due to increase in drug usage and polypharmacy

Question 3

2 types of cutaneous drug reactions

Answer 3

immunological reactions

non-immunological

Question 4

what is the presentation of immunological reactions

Answer 4

allergic, not dose-dependent 
Type 1 = anaphylaxis, urticaria 
Type 2 = cytotoxic reactions (pemphigus and pemphigoid)
Type 3 = purpura rash 
Type 4 = rash, erythema

Question 5

what is the presentation of non-immunological reactions

Answer 5

Mostly exanthematous, morbilliform, maculopapular 
Occasionally is urticaria
Also can be papulosquamous, pustular, 
bullous, pigmentation, 
itch,
pain,
photosensitivity 
CONSIDER any patient taking medication who suddenly develops a SYMMETRICAL skin eruption

Question 6

How do you identify the problematic drug when the patient is on multiple drugs?

Answer 6

1. Identify drug that is known to be the most likely to cause an eruption
2. Time the interval between exposure and development of the skin reaction
3. Look at history of previous exposure to the same drug

Question 7

what is a exanthematous drug eruption?

Answer 7

most common type of drug eruption - 90%

Question 8

How does exanthematous drug eruption present?

Answer 8

Widespread symmetrically distributed rash, distinctive [idiosyncratic], type IV reaction
Usually nothing on mucous membranes
Onset is 4-21 days after first taking drug
Usually mild and self-limiting
Itch and mild fever are common
Can progress to a severe, life-threatening reaction

Question 9

what are the indicators an exanthematous drug eruption will be severe?

Answer 9

involvement of face and mucous membrane, 
facial erythema and oedema, 
widespread confluent erythema, 
fever >38.5°C, 
skin pain, 
blisters, 
purpura, 
necrosis, 
lymphadenopathy, 
arthralgia, 
SOB, wheezing

Question 10

What drugs are associated with exanthematous drug eruptions?

Answer 10

penicillins 
sulphonamides 
erythromycin 
streptomycin 
allopurinol 
anti-epileptics 
NSAIDs 
chloramphenicol

Question 11

what is a urticarial drug eruption?

Answer 11

usually a type 1 reaction after re-challenge with drug
OR
direct release of inflammatory mediators from mast cells on first exposure i.e. NO hypersensitivity reaction

Question 12

how does a urticarial drug eruption present?

Answer 12

can be associated with angioedema or anaphylaxis

Question 13

what is a pustular/bullous drug eruption?

Answer 13

linear IgA disease

ranges from mild to severe

Question 14

what drugs can cause drug-induced bullous pemphigoid?

Answer 14

Gliptins
penicillin
furosemide

Question 15

What is acneiform and what drugs can cause it?

Answer 15

steroid acne 
caused by 
androgens
lithium 
isoniazid 
phenytoin

Question 16

What is AGEP and what drugs cause it?

Answer 16

acute generalised exanthematous pustulosis

it's very rare 
caused by 
antibiotics 
CCBs
anti-malaria drugs

Question 17

what is a fixed drug eruption?

Answer 17

a well demarcated round/ovoid plaque

Question 18

how does a fixed drug eruption present?

Answer 18

Can present as eczematous lesions, papules, vesicles or urticaria
Residues with PERSISTENT pigmentation when the drug is stopped
On hands, genitals, hips, sometimes oral mucosa
Can reoccur at same site on re-exposure to drug
Red and painful

Question 19

what drugs can cause a fixed drug eruption?

Answer 19

tetracycline
doxycycline
NSAIDs
caramazepine

Question 20

name 4 severe drug reactions which have cutaneous and systemic symptoms

Answer 20

Stevens-Johnson syndrome (SJS )
toxic epidermal necrolysis (TEN)
Drug reaction with eosinophilia and systemic syndrome (DRESS)
Acute generalised exanthematous pustulosis (AGEP)

Question 21

What is a phototoxic drug reaction?

Answer 21

a non-immunological reaction that happens when someone is exposed to enough phot-reactive drug and light of the appropriate wavelengths (usually UVA/visible light)

Question 22

what causes a phototoxic drug reaction?

Answer 22

drugs
immunosuppression/lupus
all can cause an increased sensitivity to sunlight

Question 23

How does an acute phototoxic reaction present?

Answer 23

skin toxicity

• phototoxicity
• systemic toxicity
• photo-degradation

Question 24

how does chronic phototoxic reaction present?

Answer 24

pigmentation
photoageing
photocarcinogeneis

Question 25

what is skin phototoxicity?

Answer 25

Immediate prickling with delayed erythema and pigmentation e.g. chlorpromazine, amiodarone
Delayed [3-5 days] erythema and pigmentation e.g. psoralens
Exaggerated sunburn e.g. thiazides, quinine [anti-malarial drug]
Increased skin fragility e.g. tetracycline, amiodarone
Telangiectasia e.g. CCBs

Question 26

How do you investigate drug skin eruptions?

Answer 26

history and physical examination usually enough 
Additional tests:
phototesting 
biopsies 
patch and photo-patch testing 
skin prick/intradermal tests

Question 27

When is skin testing noe indicated for drug eruptions

Answer 27

serum sickness reactions e.g. type III

severe cutaneous drug interactions - they can potentially trigger SJS, TEN and DRESS

Question 28

How is a drug eruption managed?

Answer 28

Discontinue drug if possible, try and use an alternative
- Usually resolves when drug is withdrawn, but there are exceptions to this rule:
- If drug cross reacts with a similar class of drugs
- Depending on half-life of drug and the ability of the drug to be retained/accumulate in tissues
Topical corticosteroids
Antihistamines if type I or there is itch
Allergy bracelets

Question 29

Who is more likely to have a drug reaction?

Answer 29

more likely to suffer a severe cutaneous reaction

Question 30

What are the most common drugs for causing drug reactions?

Answer 30

doxycycline
amiodarone
chlorpromazine
quinine