SKIN REACTIONS TO ANTIBACTERIAL AGENTS IN GENERAL-PRACTICE

Objectives: To quantify the risk of skin reactions to antibacterial dr ugs under everyday circumstances in a large population with automated data from general practitioners (GP). Design: A retrospective cohort s tudy in a dynamic population. Setting: Data came from the Integrated P rimary Care Information (IPCI) database. The IPCI database consists of all data on consultations, moroidity, and prescriptions and other int erventions, as registered by the GP in a source population of approxim ately 150,000 persons. Methods: The study period started on April 1, 1 994, and ended on September 30, 1995. Pill patients who were treated w ith an antibacterial drug were enrolled on the first day of starting t reatment until the end elf the study period or until the occurrence of one or more of the following diagnoses within the risk period: allerg ic reaction, rash, erythema, pruritus and urticaria, or a notification of a skin reaction in the free text. Subsequently, patient profiles w ere assessed by two authors who were blinded to exposure. The risk per iod was defined as the legend duration of the antibacterial drug plus 14 days to control for carry-over of drug effects and delay in patient presentation. Age, gender, and comedication were examined as potentia l confounders. Results: In the study period 13,679 patients received 1 9,961 prescriptions of an antibacterial drug. It concerned 5330 men (3 9.0%) and 8349 (61.0%) women with a mean age of 41 and 42 years, respe ctively. One hundred thirty-five patients developed a skin reaction in the risk period. Rash, pruritus, urticaria, and miscellaneous skin re actions were encountered in 76 (56.3%), 18 (13.3%), 19 (14.1%), and 22 (16.3%) patients, respectively. The three most frequently reported ca uses of skin reactions were combinations of trimethoprim with sulfonam ides (2.1% of users; incidence density [ID]: 2.1/1000 exposed days), f luoroquinolones (1.6% of users; TD: 1.5/1000 person days), and penicil lins (1.1% of users; ID: 1.3/1000 person days). Compared to tetracycli nes, the broad-spectrum penicillins showed an incidence density ratio (IDR) of 3.7, the combination of amoxicillin with clavulanic acid of 3 .3, the fluoroquinolones of 2.8, and the combination of trimethoprim w ith sulphonamides of 4.4. The presence of infectious mononucleosis inc reased the risk of rash in amoxicillin users with a factor of 58. Conc lusions: We found that the frequency of skin reactions to antibacteria l drugs in general practice is around 1% and highest for the combinati on of trimethoprim with sulphonamides, penicillins, and fluoroquinolon es. The outpatient incidence for skin reactions is probably lower than the incidence in hospitalized patients. Although this may be partly e xplained by negative misclassification, it is also likely that the act ual incidence is lower as some hospitalized patient groups may be more prone to develop a skin reaction. (C) 1998 Elsevier Science Inc.