Athletes often take pain relievers to help cope with pain after intense exercise, including a condition called delayed-onset muscle soreness. But NSAIDs haven't been shown to help with that problem, Warden said. Instead, runners should try gentle exercise, such as using a stationary bike or running in water, he said. Sprinting and normal running should be avoided.
Ibuprofen (Advil and Motrin) and another NSAID, naproxen (Aleve), are recommended for pain relief and reducing fever. Best tolerated when taken on a full stomach -- rare during a marathon -- they work by stopping the body's production of a substance that causes pain, fever and inflammation.
But that substance, prostaglandin, is also important for the synthesis of collagen, Warden said. "Collagen is the main structural material of all muscles, bones and tendons," he said. "That's what gives [them] strength. The drugs can reduce how much collagen you form in response to exercise."
Acetaminophen has a weaker anti-inflammatory effect than the NSAIDs and is often classified as an analgesic, or pain reliever. The drug changes the way the body senses pain and has a cooling effect, according to the National Institutes of Health.
Both types of medicines have risks and potential side effects, especially when misused. (Experts are less concerned about aspirin, also an NSAID, but say it's best to avoid routinely taking any kind of painkiller before running.)
With the exception of aspirin, NSAIDs can increase the risk of heart attack and stroke, and taking them while dehydrated can cause gastrointestinal pains and overwhelm the kidneys.
"There's absolutely a role for anti-inflammatories like Motrin, Advil and Aleve, but you have to understand when they're necessary and when you should take them, said Dr. George Chiampas, medical director for the Chicago Marathon. "And more is definitely not better."
Taking too much acetaminophen -- a common mistake because it's often found in combination products -- can cause liver damage. Last year, Tylenol's manufacturer lowered the recommended daily maximum dose of Extra Strength Tylenol from eight 500 mg tablets to six to reduce the risk of an accidental overdose.
Soreness is one of the least welcome side effects of exercise, but the pain is a signal that some tissue irritation or damage has occurred, said Warden. Masking that pain can lead to a more serious injury.
By the same token, inflammation is a natural part of the healing process and speeds up tissue repair. A chemical release at the injured site attracts cells that will clean up the area and heal it, said Warden.
The inflammation response often is overzealous, Warden said, and drugs can be used to control it. "But once the inflammatory signs are gone, you don't need anti-inflammatories," he said.