Side effects of certain antibiotics, including widely used drugs like Bactrim or Cipro, may increase the risk of developing kidney stones, according to the findings of new research. 

In a study published by the Journal of the American Society of Nephrology on May 10, researchers from Children’s Hospital of Philadelphia found signs that five different types of antibiotics were associated with an increased risk of kidney stone development.

Researchers used electronic health data from 641 general practices, including medical records for 13 million children and adults from 1994 to 2013 in the United Kingdom. They matched 26,000 patients with kidney stones to 260,000 control patients to examine 12 classes of oral antibiotics and their link to the development of kidney stones, known as nephrolithiasis.

Five of the 12 classes of antibiotics were associated with increased risk of developing kidney stones. Risk was increased between 1.3 to 2.3 times depending on the type of antibiotics.

Exposure to Sulfonamides, like Bactrim; cephalosporins, like Keflex; fluoroquinolones, like Cipro and Levaquin; nitrofurantoin/methenamine, like Macrobid and Hiprex; and broad spectrum penicillin all increased the risk of developing kidney stones. The other classes of antibiotics carried no increased risk.

The increased risk of kidney stones after antibiotic use lasted for 3–5 years. Additionally, the link between antibiotic use and kidney stones was especially seen among patients who were younger. And penicillin only increased the risk of kidney stones for those under the age of 75.

Other studies have shown a link between antibiotic use and kidney stones, but this is the first study to indicate which classes of antibiotics are associated with the most risk.

Kidney stones develop from a mineral build up in the urine. Sometimes the buildup causes solid small pebbles, or “stones, to “ form. Those stones can pass through the urinary tract without a person knowing or the person can experience blood and sharp pains in the abdomen and groin as they pass.

Kidney stones can take anywhere from a few weeks to several months to form. The incidence of kidney stones has increased 70% over last 30 years, which many speculate is the result of the increase in antibiotic use and prescriptions.

In 2011, doctors in the U.S. prescribed 262 million courses of antibiotics. Researchers speculate antibiotics may change the bacterial makeup of the urinary tract, upsetting the balance of the micro biome of the gut, potentially leading to kidney stones.

While there was an increased risk with the five classes noted, researchers warned patients not to stop taking antibiotics when they are necessary.

Tags: Antibiotics, Bactrim, Cipro, Fluoroquinolone, Hiprex, Keflex, Kidney Stones, Macrobid