Antibiotics Tied to Higher Kidney Stone Risk

 If you or your child is taking an antibiotic, new research suggests you might want to watch closely for signs that kidney stones might be developing.

"We found that five classes of commonly prescribed antibiotics were associated with an increased risk of kidney stones," explained study author Dr. Gregory Tasian.

That increased risk appeared to linger for three to five years, and pediatric patients were the most vulnerable to developing the painful condition.

The findings echoed those of prior studies, "although we did not know which specific classes of antibiotics would be associated with an increased risk of stones and which ones would not," Tasian added.

Tasian is an assistant professor of urology and epidemiology with the University of Pennsylvania Perelman School of Medicine.

The five antibiotic classes newly linked to kidney stone risk included sulfas (Bactrim, Gantanol); cephalosporins (Keflex); fluoroquinolones (Cipro); nitrofurantoin/methenamine (Macrobid, Hiprex); and broad-spectrum penicillins. No risk was observed among seven other classes of oral antibiotics.

Tasian stressed that this doesn't mean people should avoid antibiotics when they're truly needed.

"Antibiotics have saved millions of lives and are needed to prevent death and serious harm from infections," he said. "The benefits outweigh the potential harms. These results don't suggest that antibiotics should not be prescribed when indicated."

However, they do support "the judicious and appropriate use of antibiotics, and reducing inappropriate use of antibiotics," Tasian noted.

One kidney expert agreed that the proper use of the drugs is a balancing act.

"This study is another reminder that physicians have to be mindful of potential adverse effects of antibiotics and need to promote appropriate antibiotic stewardship. This is especially true since many antibiotics may be unwarranted," said Dr. Maria DeVita, training program director for nephrology at Lenox Hill Hospital in New York City.

According to the U.S. National Institute of Diabetes and Digestive and Kidney Diseases, kidney stones arise following mineral build-up in a patient's urine.

In some cases, small solid pebbles pass through the urinary tract without symptoms, while other people experience blood in the urine alongside sharp pain in the back, side, lower abdomen or groin.

Tasian noted that over the last three decades kidney stone incidence has skyrocketed by 70 percent, largely among children and adolescents.

Experts are unclear as to why. But prior research has cited a possible association with disturbances in the bacterial makeup (microbiome) of the intestinal and urinary tracts, which is often sparked by antibiotics.

And antibiotic prescriptions are increasingly common. As the researchers noted, in 2011, American doctors prescribed 262 million courses of antibiotics, with women and children forming the largest pool of recipients.

With that in mind, investigators used British health care data to isolate kidney stone cases among millions of patients treated by 641 general health care practitioners between 1994 and 2015. Roughly 26,000 kidney stone patients were identified.

The team then examined whether or not any of these patients had been prescribed any of 12 different classes of oral antibiotics in the three to 12 months leading up to their kidney stone.

This lengthy time frame was chosen because kidney stones can take weeks or even months to form.

The risk for kidney stones was greatest within three to six months following an antibiotic regimen, before ratcheting down over the ensuing three to five years.

Specifically taking sulfa antibiotics, cephalosporins, fluoroquinolones, nitrofurantoin/methenamine, and broad-spectrum penicillins were linked to a 1.3 to 2.3 times greater risk for kidney stones, the investigators noted.

But the study did not prove that these drugs caused kidney stones.

"For those five classes of antibiotics, the greatest risk was found among younger patients," said Tasian. "However, the increased risk was still significant across all ages, including for older adults with the exception of broad-spectrum penicillins, which were not associated with an increased risk of kidney stones among patients over 75 years of age.

"At this time, we do not have any ways to limit the risk associated with antibiotics," Tasian said. But he added that his work may eventually "provide additional insight into how, ultimately, we might be able to restore a healthy microbiome, or mitigate the adverse changes that exposure to certain antibiotics cause."

The findings were published online May 10 in the Journal of the American Society of Nephrology.