Drug hypersensitivity

Adverse drug reactions (ADRs) are everyday occurrences in both in- and outpatient practice settings. Based on a recent meta-analysis, the overall incidence of ADRs in hospitalized patients was 15.1%, with nearly half of these reactions being serious in nature [1]. The incidence of fatal ADRs was found to be 0.32%, a figure that the authors estimated translates to 106,000 deaths annually in United States hospitals [1]. Although there are less data on the incidence of ADRs in the outpatient setting, two recent studies found that between 17% and 25% of ambulatory primary care clinic patients reported ADRs, and more than half of these were considered serious [2,3]. Allergic drug reactions are ADRs that are known (or presumed) to be mediated by an immunologic mechanism. They are thought to account for approximately 6% to 10% of all ADRs [4]. Because of space limitations, this review does not address the entire spectrum of drug hypersensitivity disorders (Box 1). Instead, the discussion focuses on the most clinically relevant reactions: to penicillins and other beta-lactam antibiotics, sulfonamides, aspirin/nonsteroidal anti-inflammatory drugs (NSAIDs), and local anesthetics. For a more comprehensive review of drug hypersensitivity, the reader is referred to two recent texts [5,6].