A new study finds that the common practice of taking ibuprofen for pain relief while competing in ultramarathons causes a large increase in acute kidney injury.
As a result, according to the study by researchers at Stanford University School of Medicine and several other institutions, people who take the painkiller ibuprofen while running very long distances double their risk of acute kidney injury.
As many as 75 percent of ultramarathoners use the nonsteroidal anti-inflammatory drug, or NSAID, in this fashion, noted Grant Lipman, clinical associate professor of emergency medicine at Stanford and lead author of the study published online last week in Emergency Medical Journal.
While most cases of acute kidney injury appear to resolve spontaneously, Lipman said, the condition has the potential to progress to renal failure.
Hypothesizing that ibuprofen would not result in an increased rate of acute kidney injury compared to placebo, Lipman and his colleagues conducted the first randomized, placebo-controlled, double-blinded study to test the use of ibuprofen in ultramarathoners.
The 89 participants who completed the trial were randomized to take either ibuprofen or a placebo during a 50-mile, or 80-kilometer, section of one of four different seven-day, 155-mile, or nearly 250-kilometer, ultramarathons. They were required to refrain from taking ibuprofen at least 12 hours prior to the 50-mile section of the race. They ran in ultramarathons either in China, Chile, Ecuador or Sri Lanka. They ran through wilderness terrain with few roads and varying topography, and they carried all their personal items for the duration of the race, including all their gear, food and clothing.
"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."
Twelve- to 36-hours later, depending on the speed of the runners, the participants were met by the researchers at the medical tent. There, they were weighed and their electrolyte levels and renal functioning were measured.
Forty-seven percent of the participants took ibuprofen, and 53 percent took the placebo.
Results showed that about 39 of the 89 participants had acute kidney injury at the end of the 50-mile section of the race. There was an 18 percent higher rate of kidney injury among those who took the drug compared to those who didn't, the study found.
Lipman called this an impressive difference. "Basically, for every five runners who took ibuprofen, there was one additional case of acute kidney injury. That's a pretty high rate," he was quoted as saying in a news release from Stanford.
Ultramarathon races have increased in popularity in recent years. The number of races worldwide reached 1,357 in 2015, with over 70,000 runners finishing these races every year. This study should cause endurance athletes and distance runners pause before taking ibuprofen while competing, Lipman said, but does not infer that the average athlete would necessarily face similar effects from taking the drug.
"Running these races tends to hurt," said Lipman, who has served as the medical director of RacingThePlanet ultramarathon events, which are held in various parts of the world, including China, Antarctica and Chile. Having seen firsthand how common it is for runners to take ibuprofen before, during and after these races to relieve pain and reduce joint swelling, Lipman has now switched to using acetaminophen, such as Tylenol, for pain relief and taking ice baths after racing.