Fluoroquinolones, a type of antibiotic, could endanger vascular health.
Howevery, they have been flagged as bringing potentially dangerous side effects.
So, in 2016, the Food and Drug Administration (FDA) "approved safety labeling changes [...] to enhance warnings about their association with disabling and potentially permanent side effects and to limit their use."
Recent longitudinal studies linked the use of these antibiotics with a significantly increased risk of aortic disease, which is a vascular condition wherein the aorta — the body's main blood-carrying vessel — is affected.
Aortic disease is characterized either by aneurism (when the artery dilates) or dissection (when it ruptures), and both of these events can be life-threatening.
A new study — led by researchers from the Karolinska Institutet in Stockholm, Lund University (both of which are in Sweden), and the Statens Serum Institut in Copenhagen, Denmark — has now confirmed some of these worrying associations.
However, lead researcher Björn Pasternak — from the Department of Medicine at the Karolinska Institutet — says that there's a ray of hope amid the general doom and gloom.
"Our results confirm the findings in the previous studies but suggest that the increased risk is not as pronounced as indicated by those studies."
The findings have been published in The BMJ.
Fluoroquinolones more than double risk
The researchers worked with data sourced from national health registers — the National Prescribed Drug Register, National Patient Register, Statistics Sweden, and Swedish Cause of Death Register — submitted between July 2006 and December 2013.
They compared the risk of aortic disease in 360,088 people treated with fluoroquinolones with the risk of developing this condition among an equal number of participants treated with a different type of antibiotic: amoxicillin.
The researchers' analysis revealed a 66 percent higher risk of developing aortic aneurism or dissection among people who had been administered fluoroquinolone antibiotics.
"This increase," the authors write, "corresponded to an absolute difference of 82 [...] cases of aortic aneurysm or dissection per 1 million treatment episodes [over a] 60-day risk period."
They admit that — similarly to previous studies — the new research was of an observational nature, and therefore it was unable to establish that fluoroquinolones caused aortic disease.
Yet Pasternak argues that the study's size and strong methodology mean that its results provide the most credible evidence unearthed to this point.
"Although the absolute risk increase was relatively small," the researchers explain, "the study's findings should be interpreted in the context of the widespread use of fluoroquinolones."
An underlying mechanism behind the link between fluoroquinolone use and aortic disease may be that these antibiotics "turn on" the activity of certain enzymes that can harm the integrity of internal tissue.
"One of the factors involved in the development of aortic disease is increased activity in tissue-degrading enzymes known as matrix metalloproteinases," explains Pasternak.
"We know that fluoroquinolones induce the activity of these enzymes," he adds, "which is also thought to underlie the more well-known adverse effect of tendon pain and rupture."
Further studies should aim to clarify whether particular types of fluoroquinolone antibiotic are more harmful to vascular health than others. Also, more focus should be placed on understanding the biological mechanisms at play, the researchers conclude.