Ibuprofen linked to kidney injury in endurance runners

July 5 (UPI) -- Stanford University researchers found that people taking ibuprofen while running very long distances double their risk of acute kidney injury.

Ibuprofen is a common non-steroidal anti-inflammatory drug, or NSAID, marketed under brand names such as Advil.

Researchers at Stanford University School of Medicine along with the University of Washington, Seattle, the University of Colorado, Harvard University and Washington University in St. Louis, worked on the study, which was published July 5 in Emergency Medicine Journal.

Researchers found that nearly 75 percent of ultramarathoners, or very long distance runners, use ibuprofen while running to relieve pain.

"Running these races tends to hurt," Dr. Grant Lipman, a clinical associate professor of emergency medicine at Stanford and director of Stanford Wilderness Medicine, said in a press release. "In medical school, we were all taught to be careful of ibuprofen because it decreases blood flow to the kidneys."

The study tested the use of ibuprofen in ultramarathoners, treating 89 participants who completed the trial with either ibuprofen or a placebo during a 50-mile stretch of one of four different seven-day, 155-mile ultramarathons.

Participants were prevented from taking ibuprofen at least 12 hours before the 50-mile stretch of the races, which took place in Sri Lanka, Ecuador, China and Chile.

"The morning of this 50-mile section of the race, the participants came to the medical tent," Lipman said. "We weighed them and gave them a baggie and said to take these pills every four hours. They were given either 400 milligrams of ibuprofen or sugar pills. Nobody knew which. And instructed to take one every four hours. And they ran off."

Researchers then tested their weight, electrolyte levels and renal function 12 to 36 hours later depending on the speed of the runners.

Results showed that 39 of the 89 participants had acute kidney injury at the end of the 50-mile stretch, an 18 percent higher rate of acute kidney injury among those who took ibuprofen compared to those who took the placebo.

"Basically, for every five runners who took ibuprofen, there was one additional case of acute kidney injury. That's a pretty high rate," Lipman said.

Acute kidney injury is common in marathon runners due to the high rate of dehydration causing reduced blood flow and rhabdomyolsis, which is a breakdown of muscle tissue leading to the release of muscle fiber contents into the blood.