(Reuters Health) - Ultramarathoners who manage race day pain with ibuprofen are a bit more likely to develop kidney injuries than their competitors who don’t use the drug, a small experiment suggests.

The difference in the odds of kidney damage wasn’t big enough to be statistically meaningful, and at least some of the added risk may be associated with dehydration, researchers report in the Emergency Medicine Journal. But it’s possible one in every 5.5 ultramarathoners using ibuprofen, in a family of medicines known as nonsteroidal anti-inflammatory drugs (NSAIDs), might experience acute kidney injuries, researchers conclude.

“In endurance events, there are multiple factors at play that may cause acute kidney injury,” said lead study author Dr. Grant Lipman of Stanford University School of Medicine in California.

“There is dehydration, which decreases renal blood flow, and also the breakdown of muscle fibers which can clog the kidneys’ filtering mechanism and lead to renal failure,” Lipman said by email. “The concern is that the hit of NSAID-induced decreased renal blood blow may add to the ‘perfect storm’ of events.”

In acute kidney injury, the kidneys are no longer able to filter waste products from blood. The condition is common in endurance runners, the study team writes in the Emergency Medicine Journal, and in most cases it resolves by itself.

For the study, researchers randomly assigned 89 elite athletes to take either 400 milligrams of ibuprofen or a dummy pill known as a placebo every four hours during a 50-mile foot race. At the end of the race, researchers measured creatinine in the runners’ blood to detect kidney injury.

Overall, 22 runners taking ibuprofen, or 52 percent, developed acute kidney injury, compared with 16 athletes, or 34 percent, with the placebo.

While that suggests kidney damage might be about twice as likely with ibuprofen than without it, the difference wasn’t big enough to rule out the possibility that it was due to chance.

Other studies have linked NSAIDs to an increased risk of acute kidney disease in healthy people who aren’t athletes. For every 100,000 NSAID users, one will develop kidney problems, previous research suggests, translating into upwards of 2.5 million cases annually.

Because endurance athletes have more risk of kidney damage than other individuals, the risks of NSAIDs may outweigh the benefits, the study authors conclude.

Ultramarathoners should use NSAIDs with caution, said Dr. Elliott Antman, a researcher at Harvard Medical School in Boston who wasn’t involved in the study.

“The basic message is avoid NSIADs if possible,” Antman said by telephone. “If you have to take them, take the smallest dose required to relieve whatever discomfort develops and take it for the shortest possible period of time.”

Another option is acetaminophen, a pain reliever that’s processed by the liver, not the kidneys, said Dr. Karen M. Sutton, a researcher at Yale University School of Medicine in New Haven, Connecticut, who wasn’t involved in the study.

Good hydration is also key, Sutton said by email.

“Ultramarathoners who are faster or suffer greater water weight loss during the run have a higher incidence of acute kidney injury,” Sutton said. “It would be important to stay very well hydrated during the run if one does take NSAIDs.”

Even some people who aren’t endurance athletes may eventually experience severe kidney damage from routine, long-term use of NSAIDs, noted Dr. Liffert Vogt, a researcher at the University of Amsterdam in the Netherlands who wasn’t involved in the study.

“The findings of this study are not only relevant for ultramarathon runners,” Vogt said by email.

“The study shows that anyone who is at risk for dehydration, for instance a senior in a nursing home during a hot summer, may suffer from a much higher risk for kidney failure when using NSAIDs,” Vogt added. “The same is true when someone gets dehydrated by a stomach flu with diarrhea and also uses NSAIDS.”

SOURCE: bit.ly/2umgXJ6 Emergency Medicine Journal, online July 5, 2017.