Achilles tendinitis associated with fluoroquinolones

Abstract

Aims. To determine whether there is an association between use of fluoroquinolones and tendinitis in a large population under everyday circumstances. Methods. A retrospective cohort study was carried out in a dynamic population. Data came from the IPCI-database which consists of all data on consultations, morbidity, prescriptions and other interventions, as registered by GPs in a source population of approximately 250,000 persons. For this study data were collected from 41 general practices in the period from January 1st, 1995 through December 31st, 1996. All persons treated with either fluoroquinolones, amoxicillin, trimethoprim, cotrimoxazole or nitrofurantoin were followed from the first day of treatment until the outcome of interest, death, transfer to another practice, or end of the study period, whichever came first. The risk window was defined as the legend duration + 1 month. Potential cases were defined as a registration of a tendinitis or tendon rupture. Patients with a history of tendinitis or tendon rupture, preceding trauma or inadequate diagnoses were excluded on the basis of a review of the patient profiles and additional clinical data, blinded as to the exposure status. Results were adjusted for age, gender, concurrent corticosteroid exposure and number of GP visits. Results. There were 1841 users of fluoroquinolones and 9406 users of the other antibacterial drugs with an average duration of 9 and 7 days, respectively. Tendinitis or tendon rupture was registered in 97 profiles, but after review only 22 complied with the case definition. The adjusted relative risk of tendinitis to fluoroquinolones was 3.7 (95% CI: 0.9-15.1) for Achilles tendinitis and 1.3 (95% CI: 0.4-4.7) for other types of tendinitis. Achilles tendinitis to ofloxacin had a relative risk of 10.1 (95% CI: 2.2-46.0) and an excess risk of 15 cases per 100,000 exposure days. Conclusions. Although the numbers in our study are small, our results suggest that some fluoroquinolones may increase the risk of Achilles tendinitis, and that this risk increase is highest for ofloxacin.