Painkillers are supposed to get rid of pain, and most of the time they fight inflammation. Even worse: Runners who'd taken ibuprofen right before the race showed signs of kidney disease, as well as endotoxemia - a dangerous condition in which toxins from the large intestine get into the bloodstream.So, how did this happen? Experts say if you take painkillers like ibuprofen and then exercise, your increased body temperature causes the drug to damage cells in your colon and kidneys. In fact, people who regularly exercise and take ibuprofen often have higher levels of toxemia. Bottom line: Stay safe. Lay off the ibuprofen when you exercise.