CUTANEOUS MANIFESTATIONS OF ADVERSE DRUG REACTIONS

Abstract

The assessment of any dermatologic condition involving the skin, hair, nails, and mucous membranes that appears within 2 weeks of starting a medication should include “drug-induced” in the differential. Few diagnoses are as challenging for physicians, however, as the documentation of a drug-induced disease. This challenge is caused by the complexity in defining and classifying the many possible types of (dermatologic) reactions that drugs can produce, compounded by the availability of an ever-increasing number of over-the-counter drugs, herbal concoctions, and prescribed medications. Adverse reactions to drugs are frequent consequences of medical therapy because few, if any, medications can produce beneficial effects without at least one adverse effect. An adverse cutaneous reaction caused by a drug is any undesirable change in the structure or function of the skin, its appendages, or mucous membranes. A drug is defined as any chemical substance or combination of substances that are ingested, injected, inhaled, inserted, instilled, or topically applied to the skin or mucous membrane. Adverse reactions may result from overdose, accumulation, pharmacologic side effects, drug–drug interactions, idiosyncrasy, microbial imbalance, exacerbation of existing latent or overt disease, Jarisch-Herxheimer reaction, hypersensitivity, autoimmune-like reaction, teratogenic effect, interaction of the drug and sunlight or other light sources, or other unknown mechanisms (see Appendix at end of article).8 To summarize all of the cutaneous manifestations of adverse drug reactions would unjustly trivialize the material already available in excellent manuals and textbooks.15, 20, 63 The Drug Eruption Reference Manual is an outstanding reference book that is useful for any practitioner who evaluates potential drug eruptions. Medline searches make available the most recent reported specific-drug and specific-cutaneous reaction. This article provides a plan for the diagnosis and management of cutaneous reactions (i.e., pruritus, flushing, urticaria, erythema multiforme, generalized maculopapular rashes, and so forth) that may be referred to an allergist for evaluation to confirm or rule out a drug-induced cause. Suspected cutaneous drug reactions are of numerous clinical types and result from various pathophysiologic mechanisms, most of which are not immunologic. Although most cutaneous eruptions are not uniquely associated with a particular drug, certain eruptions have particular drugs that are commonly associated with their cause (i.e., fixed drug eruptions and tetracycline). Thus, the clinical assessment of each eruption is essential in determining the probability of a drug-induced cause.