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Cutaneous Adverse Drug Reaction 227

Cutaneous Adverse Drug Reaction
VetBooks.ir Diseases and Disorders

by erythematous maculopapules and flat
BASIC INFORMATION
confirming the diagnosis.
or raised annular or polycyclic lesions, with (53%-100%). It should not be used for
Definition minimal epidermal detachment. SJS/TEN
Development of cutaneous or mucocutaneous involves widespread erythema, blistering, and Differential Diagnosis
lesions after drug administration (topical, oral, severe epidermal detachment. • Erythroderma/exfoliative dermatitis: epith-
inhalation, or injectable). The lesions may be • Fixed reactions: well-demarcated erythe- eliotropic lymphoma
limited to the cutaneous/mucocutaneous areas matous lesions sometimes associated with • Urticaria/angioedema, maculopapular erup-
or may be part of a systemic reaction. These blistering and necrosis tions, pruritus: hypersensitivity disorders,
uncommon reactions can be predictable (phar- • Injection-site reactions: local reaction ectoparasitosis, superficial bacterial or fungal
macologic) or unpredictable (idiosyncratic). characterized by alopecia, inflammation, infection, and mast cell tumor
necrosis, or ulceration • Autoimmune skin diseases: spontaneous
Synonyms • Vasculitis: purpura, necrosis, and punctate autoimmune disease not related to drugs
Drug eruption, drug allergy ulcers, especially localized over extremities, (more common)
pressure points, and oral mucosa; may be • EM and SJS/TEN: superficial and deep
Epidemiology painful (p. 1031) infection (bacterial and fungal), urticaria,
SPECIES, AGE, SEX • Sweet and Wells syndromes: characterized by autoimmune skin diseases, burns, ulcerative
The incidence of cutaneous adverse drug a neutrophilic and eosinophilic dermatitis, stomatitis, and epitheliotropic lymphoma
reactions (CADRs) in dogs and cats with respectively. Erythema, plaques, nodules; may • Fixed reactions: contact dermatitis, hyper-
skin diseases has been reported as 2% and be painful sensitivity disorders, pyoderma, and fungal
1.6%, respectively. It is likely that many cases • Contact dermatitis: edema, erythema, infection
of CADR go unrecognized and unreported. papules, and vesicles localized in the • Injection-site reactions: traction alopecia,
area of direct contact with the offending hypersensitivity disorders, pyoderma, der-
GENETICS, BREED PREDISPOSITION drug. Secondary lesions may develop with matophytosis, alopecia areata, and neoplasia
No clear breed predisposition chronicity. • Vasculitis: urticaria, autoimmune skin
diseases, EM, SJS/TEN, disseminated
RISK FACTORS Etiology and Pathophysiology intravascular coagulation, coagulopathy,
The number of drugs administered, a concomi- • Although some drugs are more frequently frostbite, and neoplasia
tant infection suppressing the immune system, associated with drug reactions (e.g., sulfon- • Contact dermatitis: ectoparasites, hyper-
or other immunosuppressive state might increase amides), any drug might cause a CADR. sensitivity disorders, bacterial overgrowth,
the risk of developing a CADR. Metabolic or • CADR may be immediate after first adminis- superficial fungal infection
enzymatic dysfunctions may predispose to a tration, after weeks to months of administra-
CADR. tion without prior apparent reaction, or a Initial Database
few days after the drug is discontinued. • History of drug administration before onset
Clinical Presentation • The predictable (pharmacologic) reactions of skin lesions (at least 7 days before develop-
HISTORY, CHIEF COMPLAINT are related to the pharmacologic actions of ment of skin lesions if never administered
• History of drug administration the drugs and are more common. They are before)
• The chief complaint is variable because of associated with the dose, the pharmacologic • Routine dermatologic diagnostics (skin
the wide spectrum of clinical signs. side effects/toxicity, or drug interactions and scrapings, skin cytology, skin biopsy, fungal
resolve when the drugs are discontinued. culture) based on differential diagnosis
PHYSICAL EXAM FINDINGS • The unpredictable (idiosyncratic) reactions • Although a wide range of histologic patterns
Several clinical presentations have been are usually considered immunologically exists in CADR, skin biopsies can help confirm
described: mediated. They can also be associated the diagnosis or exclude differential diagnoses.
• Erythroderma/exfoliative dermatitis: localized with individual genetic differences in the
or diffuse erythema that can lead to scales, metabolism of drugs, leading to inappropriate Advanced or Confirmatory Testing
crusts, and alopecia generation or accumulation of toxic metabo- • Suspected vasculitis: rickettsial titers, if other
• Urticaria/angioedema: edematous papules lites (e.g., MDR1/ABCB1-Δ gene mutation clinical signs suggestive
and wheals or hives; variable erythema and [p. 638] in collies and other herding breeds). • Suspected systemic lupus erythematosus:
pruritus. Angioedema is usually localized to antinuclear antibody test
head and face. DIAGNOSIS • Cats: feline immunodeficiency virus (FIV)/
• Maculopapular eruptions: usually erythe- feline leukemia virus (FeLV) serology
matous, pruritic or not Diagnostic Overview
• Pruritus: localized or widespread, can lead • The key elements necessary for identifying a TREATMENT
to self-induced lesions CADR are a thorough history, including drug
• Autoimmune-like (pemphigus-like, pemphi- administration and appropriate timing for Treatment Overview
goid reactions, lupus-like reactions): clinical the development of skin eruptions; a lack of Stop the pharmacologic or immunologic reac-
presentation varies from pustules and crusts alternative explanations for the lesions; and tions causing the drug eruption.
to vesicles, bullae, and ulcers, depending on dechallenge, with resolution of skin lesions
the autoimmune dermatosis mimicked. within 1-2 weeks. Rechallenging with the Acute General Treatment
• Erythema multiforme (EM) and Stevens- suspected drug confirms the diagnosis but • Discontinue use of the offending medication
Johnson syndrome/toxic epidermal necrolysis is generally not recommended. and other chemically related medications.
(SJS/TEN): spectra of diseases manifested • A human drug scoring system has been • Supportive care as needed (e.g., fluid therapy,
by an acute reaction pattern of skin and evaluated in veterinary dermatology. It has nutritional support, analgesics, antipruritic
mucous membranes. EM is characterized variable sensitivity (0%-50%) and specificity therapy, wound care)

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