Drug Eruptions Flashcards
What are examples of a cutaneous manifestation of type 1 hypersensitivity?
Urticaria
Eczema
Psoriasis
What are examples of a cutaneous manifestation of type 2 hypersensitivity?
Pemphigus and pemphigoid
What are examples of a cutaneous manifestation of type 3 hypersensitivity?
Purpura, rash
What are examples of a cutaneous manifestation of type 4 hypersensitivity?
Erythema, rash
Is a drug-induced type 4 hypersensitivity reaction dose-dependent (and what does that mean)?
No - it can’t be helped by taking a smaller dose of the drug causing the reaction
What are the different types of clinical presentation of a drug-induced reaction?
Exanthemous/maculopapular Urticarial Papulo-squamous/pustular/bullous Pigmentation Itch/pain Photosensitivity
When should you consider a drug-induced reaction?
Any patient taking medication who suddenly develops a symmetrical skin eruption
Usually resolves when the drug is withdrawn
What are patient risk factors for a drug-induced reaction?
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
What are drug risk factors for a drug-induced reaction?
Drug biochemistry - beta-lactam compounds, NSAIDs, high molecular weight
Route of administration
Dose
Kinetics/half-life
What factors should be considered when trying to identify which drug is causing a reaction in a patient on multiple drugs?
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
What is the most common type of drug reaction?
Exanthematous
What are exanethmatous drug reactions?
Type 4 hypersensitivity - delayed
Mild and self-limiting
Idiosyncratic
How do exanthematous drug reactions present?
Widespread symmetrically distributed rash
Pruritis is common
Mild fever is common
Mucus membranes usually spared
When are exanthematous drug reactions usually onset?
4-21 days after first taking drug
What are indicators pf a potentially severe and life-threatening exanthematous drug reaction?
Involvement of mucous membranes and face Widespread confluent erythema Fever Skin pain Blisters, purpura, necrosis Lymphadenopathy, arthralgia Shortness of breath, wheezing
What are some drugs associated with exanthematous drug reactions?
Penicillins NSAIDs Sulphonamides Erythromycin Allopurinol
What are urticarial drug reactions?
Usually type 1 hypersensitivity reactions - allergy
Produce urticaria, may be associated with angioedema or anaphylaxis
What are the two ways drugs can cause an urticarial reaction?
After re-challenge with drug
Direct release of inflammatory mediators from mast cells on first exposure
What are examples of drugs that produce an urticarial reaction after re-challenge with drug?
Beta-lactams
Carbamazepine
What are examples of drugs that produce an urticarial reaction due to direct release of inflammatory mediators from mast cells on first exposure
Aspirin Opiates NSAIDs Muscle relaxants Vancomycin Quinolones
What is the difference between the presentations of acneiform drug reactions and acne?
In drug reactions the skin is not shiny - clue that it is not acne
What are examples of drugs that cause acneiform drug reactions?
Glucocorticosteroids
Androgens
What is acute generalised exanthematous pustulosis, and what drugs can it be caused by?
Rare pustular drug eruption Can look like pustular psoriasis Antibiotics Calcium channel blockers Anti-malarials
What drugs can cause drug-induced bullous pemphigoid?
ACE-inhibitors
Penicillin
Furosemide
What is the presentation of fixed drug eruptions?
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
What are drugs associated with fixed drug eruptions?
Tetracycline, doxycycline
Paracetamol
NSIADs
Carbamazepine
What are the different severe cutaneous adverse drug reactions?
Stevens-Johnson syndrome
Toxic epidermal necrolysis
Drug reaction with eosinophilia and systemic symptoms
Acute generalised exanthemous pustulosis
How do acute phototoxic drug reactions present?
Skin toxicity - photosensitivity
Systemic toxicity
Photodegredation
How do chronic phototoxic drug reactions present?
Pigmentation
Photoageing
Photocarcinogenesis
What is a phototoxic drug reaction?
A non-immunological skin reaction arising an individual exposed to enough photo reactive drug and light of the appropriate wavelength
What can increased sensitivity to sunlight be caused by?
Drugs
Immunosuppression
Lupus
What are some patterns of skin phototoxicity?
Immediate prickling with delayed erythema and pigmentation
Exaggerated sunburn
Exposed telangiectasia
Delayed 3-5 days erythema and pigmentation
Increased skin fragility
What are some drugs associated with phototoxic drug reactions?
Antibiotica Thiazodes NSAIDs Amiodarone Antifungals Immunosuppressants
What are important things to know in a history of a drug reaction?
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
What investigations should be done for a drug reaction?
History and examination usually sufficient
Phototesting for suspected phototoxic reactions
Biopsy
Patch and photo-patch tests
Skin prick test for specific drugs
What is the management for a drug reaction?
Discontinue drug if possible Use alternative Topical corticosteroids Anti-histamine if type 1 or symptoms of itch Allergy bracelets
