Drug reactions and the skin Flashcards
Drug reactions are immunologically/non-immunologically mediated?
Non-immunologically mediated
Typical presentation
Patient who takes medication and develops a sudden symmetric skin eruption which usually resolves when the causative drug is withdrawn
Who is most susceptible?
Extremes of age
Females
Patients with other associated diseases
Patients who have suffered from drug reactions before
Common drugs which cause a skin reaction
NSAIDs
B-lactam compounds
Exanthematous drug eruptions
Most common
Mild, self limiting
Which type of hypersensitivity reaction is an exanthematous drug eruption?
Type IV
Exanthematous drug eruptions - morphology
Flat Erythematous macules/patches with patches Varies in size, usually widespread Can become confluent Symmetrical distribution
Exanthematous drug eruptions - symptoms
Itch, fever
Exanthematous drug eruptions - mucosal involvement is usually present/absent ?
Absent
Exanthematous drug eruptions - onset
4-21 days after taking first dose
Exanthematous drug eruptions - causative drugs
penicillins sulphonamide antibiotics erythromycin streptomycin allopurinol carbamazepine NSAIDs phenytonin chloramphenicol
Which type of hypersensitivity reaction is an urticarial drug eruption?
Type I
Urticarial drug eruption - morphology
Raised
Itchy rash
Urticarial drug eruption - onset
Up to 3 weeks after first exposure / minutes on re-challenge testing
Urticarial drug eruption - causative drugs
b-lactam antibiotics aspirin opiates NSAIDs vancomycin quinolones
Pustular/bullous drug eruptions - AGEP
Acute Generalised Exanthematous Pustulosis
Rare, severe
Pustular/bullous drug eruptions - AGEP morphology
Superficial pustules (small blisters filled with fluid)
Red rash
Usually starts on face/armpits/groin
Pustular/bullous drug eruptions - AGEP causative drugs
CCB
Tetracyclines
Anti-malarials
Pustular/bullous drug eruptions - Acne causative drugs
Glucocorticoids Androgens Lithium Isoniaside Phenytonin
Pustular/bullous drug eruptions - Bullous pemphigoid morphology
Severe itch with large fluid filled blisters which can rupture to cause crusted erosions
Pustular/bullous drug eruptions - bulls pemphigoid causative drugs
ACE inhibitors
Penicillin
Furosemide
Fixed drug eruptions - morphology
Well demarcated oval plaques
May have central blisters
Red, painful
Fixed drug eruptions - areas commonly affected
Mucosal surfaces such as lips, hands, genitalia
Fixed drug eruptions - causative drugs
Paracetamol NSAIDs Tetracycline Doxycycline Carbamazepine
Phototoxic drug eruptions
Lots of prescribed drugs absorb light which can make many patients light sensitive.
Can occur indoors through window glass (UVA)
Phototoxic drug eruptions - acute presentation
Skin toxicity
Photodegradation
Phototoxic drug eruptions - chronic presentation
Pigmentation
Photo ageing
Phototoxic drug eruptions - chlorpromazine, amiodarone
Immediate prickling with delayed erythema
Phototoxic drug eruptions - quinine, thiazides
Exaggerated sunburn
Phototoxic drug eruptions - calcium channel antagonists
Telangiectasia
Phototoxic drug eruptions - amiodarone
Increased skin fragility
Management of a drug eruption
Ideally stop the drug and use an alternative
Topical steroids
Anti-histamines
