blockers have variable degrees of selectiv-ity for the β1-receptors. Those that are more β1 selec-tive have less influence on
bronchopulmonary and vascular β2-receptors (Table 14–3). Theoretically, a selective β1-blocker would have less of an
inhibi-tory effect on β2-receptors and, therefore, might be preferred in
patients with chronic obstructive lung disease or peripheral vascular disease.
Patients with peripheral vascular disease could potentially have a decrease in
blood flow if β2-receptors,
which dilate the arterioles, are blocked. β-Receptor blocking agents also reduce
intraocular pressure in patients with glaucoma.
also classified by the amount ofintrinsic sympathomimetic activity (ISA) they
have. Many of the β-blockers have some agonist activity; although they
would not produce effects similar to full agonists (such as epinephrine), β-blockers with
ISA may not be as beneficial as β-blockers without ISA in treating
patients with cardiovascular disease.
β-Blockers can be
further classified as thosethat are eliminated by hepatic metabolism (such as
metoprolol), those that are excreted by the kid-neys unchanged (such as
atenolol), or those that are hydrolyzed in the blood (such as esmolol).