An adverse drug reaction is any nontherapeutic deleterious effect due to a prescribed or over-the-counter medication or vaccine. Drug eruptions can mimic almost any dermatosis. Such reactions may be allergic (immunologic) or nonallergic (toxic). Allergic drug reactions are not dose dependent. They are classified as one of four types of immunologic reactions:
Type I: classic immediate hypersensitivity (urticaria, angioedema, anaphylaxis)
Type III: immune complex (vasculitis, serum sickness, urticaria, angioedema)
Type IV: delayed hypersensitivity (contact dermatitis, exanthematous reactions, photoallergic reactions)
Nonallergic drug eruptions are more common than allergic-type eruptions; they may be dose related, idiosyncratic, localized cutaneous, or systemic. Localized cutaneous eruptions are most often secondary to topical medications such as benzoyl peroxide or topical retinoids. Systemic reactions include symptoms of vertigo secondary to high-dose minocycline. Drug reaction with eosinophilia and systemic symptoms (DRESS syndrome) and acute generalized exanthematous pustulosis (AGEP) are examples of nonallergic idiosyncratic reactions.
Allergic drug eruptions are most often due to antimicrobial agents, nonsteroidal anti-inflammatory drugs (NSAIDs), cytokines, biologics, chemotherapeutic agents, and psychotropic agents. Allergic drug reactions typically result in urticaria, angioedema, and/or potentially fatal anaphylaxis.
The spectrum of adverse cutaneous drug reactions varies widely and includes alopecia due to chemotherapeutic drugs and beta blockers, bullous reactions secondary to furosemide, pigmentary alterations due to antimalarials, thrombocytopenia and necrosis from heparin, and contact dermatitis due to topical neomycin.
In this Chapter…