Posted by ed_uk on February 2, 2005, at 9:09:06
In reply to Re: Beta Blockers and Tachycardia » KaraS, posted by ed_uk on February 2, 2005, at 7:22:06
Beta blockers....
By convention, a beta blocker is described as being 'cardioselective' when it has a greater affinity for beta-1 receptors than beta-2 receptors. The majority of beta-1 receptors are found in the heart (not all beta-1 receptors are found in the heart however). Beta-2 receptors are present in the airways, the heart, the uterus, peripheral blood vessels etc.
Nebivolol, bisoprolol, atenolol, metoprolol, acebutolol are all beta-1 selective. They are not totally specific for beta-1 receptors however, because they also have low affinity for beta-2 receptors.
Most beta-1 selective.... nebivolol > bisoprolol > atenolol, metoprolol > acebutolol ....least beta-1 selective.
Whether or not a beta-blocker penetrates the blood brain barrier in large quantities does NOT have anything to do with its cardioselectivity (its beta-1 selectivity). Lipophilic beta-blockers such as propranolol can readily enter the brain, water soluble beta blockers such as atenolol enter the brain in small quanties only.
Ed.
poster:ed_uk
thread:448161
URL: http://www.dr-bob.org/babble/20050202/msgs/451645.html