Clinical significance of beta 1-selectivity and intrinsic sympathomimetic activity in a beta-adrenergic blocking drug.

Almost all beta-adrenergic blockers, regardless of their pharmacologic characteristics, appear to have blood pressure-lowering activity in hypertensive patients. Comparisons between nonselective beta-blocking agents, such as propranolol and nadolol, with beta 1-selective drugs, such as metoprolol, atenolol and acebutolol, have demonstrated close similarities in their antihypertensive effects in patients. Similarly, beta blockers with and without intrinsic sympathomimetic activity (ISA) have comparable antihypertensive effects. However, beta-selective agents may offer some advantages over conventional beta blockers in hypertensive patients with concurrent conditions such as chronic obstructive airways disease, peripheral vascular disease, diabetes and hyperlipidemia. Beta 1-selective drugs are also preferred in diabetic patients receiving hypoglycemic agents because they do not interfere with glycogenolysis. Agents lacking ISA, such as propranolol, acutely increase peripheral resistance. beta blockers with ISA usually lower resistance. ISA may also minimize the bradycardia frequently found in elderly patients. Agents with ISA may protect against the decrease in high density lipoprotein cholesterol and the modest increase in triglycerides noted with some beta blockers that do not have ISA. Thus, in a large number of clinical situations in which hypertension is found, the properties of beta 1 selectivity and ISA allow beta blockers to be used with greater safety. Therefore, agents possessing both of these properties may be particularly valuable.