Before signing off on that prescription for a fluoroquinolone, family physicians may wish to consider an alternative, as yet another possible side effect has surfaced for patients who take these broad-spectrum antibiotics.
According to a study(jama.jamanetwork.com) published last month in JAMA: The Journal of the American Medical Association (JAMA), patients who take fluoroquinolones are at increased risk for retinal detachment -- and its attendant threat of irreversible vision loss -- although the absolute risk for developing the condition remains small.
Study researchers used the British Columbia Linked Health Database, which includes data on about 4.5 million people, to identify a nested case-control cohort of all patients who visited an ophthalmologist in the province of British Columbia between January 2000 and December 2007. Of the 989,591 individuals that comprised this group, researchers identified 4,384 cases of retinal detachment and 43,840 corresponding controls. Patients with a physician service claim or procedure code related to endophthalmitis were excluded from the study.
- A recent study in JAMA: The Journal of the American Medical Association found that oral fluoroquinolones raise the risk of retinal detachment in current users of the drugs.
- The antibiotics previously have been found to have a destructive effect on connective tissue, which the study authors suggest could be the source of the problem.
- The authors estimate that 1,440 cases of retinal detachment diagnosed each year in the United States may be attributed to oral fluoroquinolone use.
The researchers found that the risk of retinal detachment was elevated only among current oral fluoroquinolone users, who were nearly five times more likely than controls to be diagnosed with retinal detachment. The absolute increase in the risk of a retinal detachment was 4 per 10,000 person-years (number needed to harm=2,500 computed for any use of fluoroquinolones).
According to the study report, "Cases were more likely to be male and were more likely to have myopia (or) diabetes or have received cataract surgery." Current users of the drugs averaged 4.8 days from the first fluoroquinolone prescription to retinal detachment. Ciprofloxacin contributed to the most cases of retinal detachment in the study, followed by levofloxacin and norfloxacin.
Although the authors acknowledge that the precise mechanism of retinal detachment with fluoroquinolones is unknown, "The putative mechanism behind a possible fluoroquinolone-induced retinal detachment may be through the destructive effect of the drugs on collagen and connective tissue," they note.
Notably, fluoroquinolones previously have been linked to tendon rupture, which was one of the findings that spurred this follow-up study. Given that the retina is attached to the cortical vitreous by a matrix of collagen fibers, and that fluoroquinolones "have been shown to interfere with collagen synthesis and disrupt the extracellular matrix outside the retina," the authors postulate that "damage from fluoroquinolones to collagen and connective tissue on the long bones may also translate to the same type of damage to other types of connective tissue, including that of the vitreous and vitreous cortex."
Overall, the annual incidence of retinal detachment in the United States is estimated to be 12 per 100,000 patients. Given an exposure prevalence of about 10 percent and assuming a similar risk increase in the general population, the study authors estimate the population-attributable risk to be about 4 percent. Thus, they estimate that 1,440 cases of retinal detachment diagnosed each year in the United States may be attributed to oral fluoroquinolone use.
PubMed Health: Retinal Detachment(www.ncbi.nlm.nih.gov)