Beta blockers are classified according to the receptors they block.
Non-selective or non-specific beta blockers
First generation beta blockers such as propranolol (and the others listed below) are non-selective or nonspecific. That means they block both beta1 and beta2 receptors and so affect the heart, lungs, vascular smooth muscles, kidneys, GI, etc.
- Propranolol,
- nadolol,
- timolol maleate,
- penbutolol sulfate,
- sotalol hydrochloride, and
- pindolol
Selective or Cardioselective beta blockers
Second generation beta blockers such as Metroprolol and the following block only Beta1 receptors and so mostly affect the heart and cause a reduction in cardiac output:
- Metoprolol (Lopressor, Toprol XL),
- Bisoprolol
- Atenolol
- acebutolol,
- esmolol,
- betaxolol,
Cardioselective beta blockers without intrinsic sympathomimetic activity (ISA) include atenolol, metoprolol, bisoprolol, and practolol. Those
Cardioselective beta blockers with intrinsic sympathomimetic activity (ISA) include celiprolol, acebutolol, and xamoterol. Also, pindolol, penbutolol. Beta-blockers with ISA mimic the effects of epinephrine and norepinephrine and can cause an increase in blood pressure and heart rate. Beta-blockers with ISA don’t reduce the resting cardiac output and heart rate as effectively as Beta-blockers without ISA.
Blockers of both Alpha and Beta- Receptors
Carvedilol selectively antagonizes alpha-1 adrenergic receptors; antagonizes beta-1 and beta-2 adrenergic receptors nonselectively. That is, Carvedilol is a selective alpha and non-selective beta blocker.
Labetalol selectively antagonizes alpha-1 adrenergic receptors; antagonizes beta-1 and beta-2 adrenergic receptors nonselectively. That is, labetalol is a selective alpha and non-selective beta blocker.
Labetalol and carvedilol work exactly the same way!
References
AFP. 2003 Mar 1;67(5):1112-1113.
Epocrates