Drug-induced skin reactions

Cutaneous drug eruptions are one of the most common types of adverse reaction to drug therapy, with an overall incidence rate of 2–3% in hospitalised patients.1–3 Almost any medicine can induce skin reactions, and certain drug classes, such as non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics and antiepileptics, have drug eruption rates approaching 1–5%.4 Although most drug-related skin eruptions are not serious, some are severe and potentially life-threatening. Serious reactions include angio-oedema, erythroderma, Stevens–Johnson syndrome and toxic epidermal necrolysis. Drug eruptions can also occur as part of a spectrum of multiorgan involvement, for example in drug-induced systemic lupus erythematosus (see Chapter 11). As with other types of drug reaction, the pathogenesis of these eruptions may be either immunological or non-immunological. Healthcare professionals should carefully evaluate all drug-associated rashes. It is important that skin reactions are identified and documented in the patient record so that their recurrence can be avoided. This chapter describes common, serious and distinctive cutaneous reactions (excluding contact dermatitis, which may be due to any external irritant, including drugs and excipients), with guidance on diagnosis and management. A cutaneous drug reaction should be suspected in any patient who develops a rash during a course of drug therapy. The reaction may be due to any medicine the patient is currently taking or has recently been exposed to, including prescribed and over-the-counter medicines, herbal or homoeopathic preparations, vaccines or contrast media. Remember that the non-drug components of a medicine, i.e. the pharmaceutical excipients, may cause hypersensitivity reactions in some patients.