Drug hypersensitivity reactions: response patterns, drug involved, and temporal variations in a large series of patients.

BACKGROUND Drug hypersensitivity reactions (DHRs) are among the most frequent reasons for consultation in allergy departments, and are becoming more common due to increasing prevalence and case complexity.

OBJECTIVE To study the clinical characteristics, drugs involved, diagnostic methods, and temporal variation of DHRs in a large series of patients over a 6-year period.

METHODS We included all patients attending our department between 2005 and 2010. The diagnosis was performed by in vivo and/or in vitro tests (basophil activation test and specific immunoglobulin [Ig] E in serum and drug provocation testing [DPT]) when indicated.

RESULTS We evaluated 4460 patients who reported 4994 episodes (mean [SD] of 1.13 [0.36] [range, 1-3] episodes per patient). Based on clinical history, 37% of the episodes were attributed to nonsteroidal anti-inflammatory drugs (NSAIDs), 29.4% to beta-lactam antibiotics (BLs), 15% to non-BLs, and 18.4% to other drugs.Analysis of the 1683 patients (37.45%) finally confirmed as allergic showed the most frequent diagnosis to be hypersensitivity to multiple NSAIDs (47.29%), followed by immediate reactions to BLs (18.12%). There was an increase in reactions to non-BLs (from 21.2% to 31.9%; P < .03) over the study period, mainly due to an increase in allergy to quinolones (from 0.5% to 6.8%; P < .02); 44% of patients were diagnosed by clinical history, 14.6% by skin tests, 10.4% by in vitro tests, and 30.8% by DPT.

CONCLUSIONS NSAIDs were the drugs most frequently involved in DHRs and the most common diagnosis was urticaria/angioedema with cross intolerance. Reactions to emerging drugs such as quinolone derivatives and radiocontrast media are becoming more common.