Fluoroquinolone use and the change in incidence of tendon ruptures in the Netherlands

Introduction: Shortly after their introduction, fluoroquinolones were assoc iated with reports of tendinitis and tendon rupture. During the past years, the number of reports has risen, possibly because of an increased use of f luoroquinolones. In this study, we describe the use of fluoroquinolones in the Dutch community and the possible public health effects of an associatio n between fluoroquinolone use and tendon ruptures. Methods: In the PHARMO drug database we identified all prescriptions for fl uoroquinolones in the period 1991-1996. The incidence of fluoroquinolone us e was expressed as the number of fluoroquinolone episodes per 1000 inhabita nts in one year, and extrapolated to the Dutch population after standardisa tion on age and gender. The annual incidence of non-traumatic tendon ruptur es in the period 1991-1996 was calculated with data from the nation-wide ho spital registry. The expected number of fluoroquinolone attributable tendon ruptures was calculated on the basis of the use of fluoroquinolones, the n umber of non-traumatic tendon ruptures and an assumed relative risk of 1.5- 10. Results: In 1996, approximately 251,000 patients experienced 318,000 episod es of fluoroquinolone use in the Netherlands. Females used more often fluor oquinolones than males, and the number of episodes increased exponentially with age. In the period 1991 through 1996, the absolute number of fluoroqui nolone episodes increased by 160%, from 122,000 to 318,000. The absolute nu mber of hospitalised tendon ruptures increased with 28%, from 768 in 1991 t o 984 in 1996. Assuming a relative risk of 1.5 to 10.0, 1 to 15 tendon rupt ures could be attributed to fluoroquinolone use in 1996. Only 7% of the obs erved increase could be attributed to the increased use of fluoroquinolones . If the total increase of hospitalised non-traumatic tendon ruptures would be attributable to the increase in fluoroquinolone use, this would mean th at the risk of non traumatic tendon ruptures to fluoroquinolones would be m ore than 250 times the risk during non-use. Conclusion: In the Netherlands, a large simultaneous increase in non-trauma tic tendon ruptures and fluoroquinolone use was observed in the period betw een 1991 to 1996. Assuming a relative risk of 1.5 to 10.0 for tendon ruptur es during fluoroquinolone use, only 0.5 to 7% of the increase in non-trauma tic tendon ruptures could be attributed to the increased fluoroquinolone us e. The increase in the incidence of non-traumatic hospitalised tendon ruptu res in the Netherlands is not likely to be explained solely by the increase d use of fluoroquinolones.