Sometimes, a drug's effect on athletic performance depends on how it's administered. Take the beta2-agonist albuterol as an example. This well-known asthma drug works by relaxing the muscles lining the bronchial tubes, allowing more air to flow into the lungs. Athletes with asthma (believe it or not, elite athletes tend to have higher rates of asthma than people in the general population) generally use inhaled albuterol to treat their symptoms, allowing them to compete without shortness of breath [source: Kindermann].
But what about athletes who don't have asthma? Could they suck in a few shots of albuterol and increase their lung capacity? According to the research, this performance-enhancing effect simply doesn't exist. In a review article published in a 2007 issue of Sports Medicine, the authors found that, in 17 of 19 clinical trials involving non-asthmatic competitive athletes, the performance-enhancing effects of inhaled beta2-agonists could not be proved. All bets are off, however, when an athlete takes albuterol orally or by injection. When administered in this fashion, albuterol has been found to have anabolic properties, which means it can help build muscle like steroids.
Another orally ingested beta2-agonist known as clenbuterol, or clen, packs an even bigger punch than albuterol. Athletes in several sports -- cycling, swimming, baseball and soccer -- have tested positive for clenbuterol use, although many have claimed that the drug could be traced to contaminated food. While clenbuterol has historically been given to animals to produce leaner meat, it has been banned for use in meat since 1991 in the U.S. and since 1996 in the European Union.