In the United States, a physician can prescribe medications for uses not approved by the Food and Drug Administration, so long as there is scientific literature to support the use. Usually the pharmaceutical company involved will only research and develop a few uses to submit to the FDA to get the medication approved for marketing. Once the medication wins FDA approval, the pharmaceutical company is only allowed to advertise it for FDA-approved uses. Beta blockers are not FDA approved for use in anxiety or stage fright, but these medications can be prescribed for this purpose because there is scientific literature to support this use. Only your physician can tell you whether beta blockers are safe for you.
Beta blockers can significantly worsen some medical conditions.
As a general rule, beta blockers should not be used in asthmatic people. Beta blockers can worsen congestive heart failure, Raynaud's syndrome, and diabetes. Musicians who take beta blockers often do so in small doses and only on special occasions, so they may experience no side effects at all from their use. But beta blockers, when used on a regular basis, can cause physical dependence. Physical dependence is when the body becomes accustomed to having a medication in the body, thus over time, more medication is required to achieve the same effect.