PAdrenoceptor Blockers

In most elderly patients with essential hypertension, cardiac output is low, and systemic vascular resistance is elevated. Therefore, most antihypertensive agents, including diuretics, produce a decrease in vascular resistance while sparing systemic flow and cardiac output. Traditional ^-adrenoceptor blockers (^-selective b-blockers) (Figure 8) are an exception as drugs such as atenolol and metoprolol lower arterial pressure by decreasing cardiac output and renin

Figure 8 Structures of ß-adrenoceptor and calcium channel blockers.

release while systemic vascular resistance remains unchanged. The use of ^-adrenoceptor blockers reduces the risk of cardiovascular events such as myocardial infarction and sudden death in patients with coronary artery disease. b-Adrenoceptor blockers are effective in decreasing mortality rate in patients with reduced systolic function and heart failure.64 Carvedilol, a b-adrenoceptor blocker with associated ^-adrenoceptor blocking properties is an effective antihypertensive medication where the ^-adrenergic blocking effect accounts for its vasodilatory effects in contrast to the bi-selective agents.

Early stage renal disease in hypertension is characterized by a decrease in renal blood flow and a relatively well-preserved GFR. Microproteinuria parallels the progression of renal disease, particularly in hypertensive patients with diabetes mellitus. Traditional b-adrenoceptor blockers further diminish renal blood flow and may decrease GFR.65 One of the main side effects of using b-adrenoceptor blockers is the disturbance of the lipid profile. Studies suggest that b-adrenoceptor blockers increase triglyceride levels and decrease HDL cholesterol levels. Those with intrinsic sympathomimetic activity have a lesser effect on triglycerides and HDL than those lacking intrinsic sympathetic activity.

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