I agree with those who point out the important difference between anti-anxiety drugs and beta-blockers. Years ago I played a Brahms viola sonata with a string player who dosed herself with a load of Valium before the concert. The performance, needless to say, was a disaster.
Unlike benzodiazipines such as Valium or Xanax (the usual anti-anxiety drugs) which directly and adversely affect the brain, beta-blockers put a lid on your native epinephrine, or Adrenalin (a brand name). They do not cloud your thinking; the effect is quite subtle. But, they can also, unfortunately, put a lid on the emotional heights reached in one's performance; one must weigh the downside of nervous energy with its upside.
The dose of propanolol, the most common generic beta-blocker, varies from individual to individual, as we all seem to carry different numbers of adrenergic receptors. So, it's wise to try some out at rehearsal. 5 mg may not touch you, except as a placebo. 20 may be better. Also, the stuff inhibits the liver's reaction to hypoglycemia, so you'd best have some orange juice or something before a big concert. The brain depends on serum glucose for adequate function. Beta-blocking drugs can also give you postural hypotension, that is, make you faint if you jump up from the artist's bench too fast.
IMHO, the best way to control performance anxiety--is to perform. There is nothing better for the jitters than to give the same concert three or four times in a week.
Sorry for all the pontification. I'm a pianist who still has a day job as an anesthesiologist.