On Aug. 15, 2008, North Korean Olympic sport shooter Kim Jong-Su was stripped of his three Olympic medals. His crime? Kim had failed a drug test, but not for the steroids that cost Marion Jones and other Olympians their prizes and, in most cases, their careers. Kim had instead tested positive for propranolol, a drug that is commonly prescribed for high blood pressure. Why would an athlete, much less one without high blood pressure, take such a drug? The answer is somewhat complex. Propranolol belongs to a class of pharmaceuticals known as beta blockers, drugs that lower blood pressure by blocking specific receptors in the sympathetic nervous system. These same receptors are activated in times of anxiety and fear, making them an ideal remedy for musicians, actors and others who struggle with performance anxiety.

Beta blockers can quell trembling hands, a pounding heart and the beads of sweat that may accompany a stressful situation. They do not prevent anxiety, but rather mask the physical manifestations of anxiety; thus, they cannot prevent a concert pianist from being nervous, but they can prevent her from appearing nervous.

Beta blockers have been used to treat high blood pressure since the 1960s, but it was only in the mid 1970s that their efficacy in concealing performance anxiety was explored. A British study tested the effects of these drugs on the performances of master string musicians by having them perform in as stressful a situation as possible - booking them in a prestigious concert hall, inviting the press to attend and recording all sessions.

The musicians performed four times each, twice on a placebo pill and twice on beta blockers. The results were astounding - the musicians not only exhibited less outward anxiety, but they also performed better. The improvement for the majority of the study's subjects was minor, but for some it was striking.

Therein lies the complexity of beta blockers - while some insist that the drugs level the playing field for otherwise talented individuals who suffer from often-crippling anxiety, others argue that permitting their use will inspire an "arms race" of sorts, in which competitors feel pressured to use the drugs when they would prefer not to, if only to remain competitive. When we examine the varying effects of beta blockers, however, this argument loses credibility; since beta blockers seem to produce a noticeable effect only in the most anxious, sharpshooters and violinists who do not experience performance anxiety have no incentive to take them.

So how exactly do beta blockers work? The drugs, also known as beta-adrenergic blocking agents, act on specific (beta) receptors in the sympathetic nervous system that are normally stimulated by hormone and neurotransmitter epinephrine. Epinephrine plays a role in the "fight or flight" response of the nervous system, preparing the body for action in emergency situations by boosting levels of oxygen and glucose that are sent to the brain and muscles. Epinephrine is also responsible for increasing heart rate in times of stress, and for suppressing non-emergency bodily processes, digestion in particular. The result is that the drugs inhibit the normal ephinephrine-mediated stress response, but have a minimal effect on resting subjects.

Beta blockers are currently banned in several sports, including archery and pistol shooting, both of which require steady, precise aim. In other sports, they are simply seen as preventing the effects of anxiety from interfering with an already accomplished person's performance. The question then becomes, of course, whether or not a person's ability to perform in a stressful situation is an integral part of the activity itself. That remains a matter for further debate.

Note: Although beta blockers are not officially approved for anxiolytic use by the U.S. Food and Drug Administration, they are available with a prescription from a doctor. They can also be found on certain sites online, although their legitimacy is somewhat dubious.