Peak effect occurs in one to one and a half hours. Ideally, this could allow a performer to play at his or her best, without the distraction or interference of excessive fight or flight symptoms. The beta receptors found in the different areas of the body are not all the same, thus different beta blockers may affect these areas differently. Thus, they can decrease blood pressure, heart rate and force of cardiac contraction, but are less likely to cause bronchoconstriction and uterine contractions. This selectivity is not absolute and depends on the dose.
Some beta blockers enter the brain better than others.
This may be why propranolol causes more central nervous system side effects, such as hallucinations, nightmares, and depression, than the beta blockers that do not cross into the brain as easily. Interestingly, the ability of beta blockers to help anxiety seems related only to their blockade of beta receptors outside of the brain. Everyone's body responds differently to beta blockers. For this reason it is important that each person experiment, under medical supervision, to find the ideal dosage for a performance situation. Similarly, it is important to take the beta blocker a few times and under different circumstances before a major performance to be sure the individual has no adverse reactions.