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

Abstract

Almost all β-adrenergic blockers, regardless of their pharmacologic characteristics, appear to have blood pressure-lowering activity in hypertensive patients. Comparisons between nonselective β-blocking agents, such as propanolol and nadolol, with β 1-selective drugs, such as metoprolol, atenolol and acebutolol, have demonstrated close similarities in their antihypertensive effects in patients. Similarly, β blockers with and without intrinsic sympathomimetic activity (ISA) have comparable antihypertensive effects. However, β-selective agents may offer some advantages over conventional β blockers in hypertensive patients with concurrent conditions such as chronic obstructive airways disease, peripheral vascular disease, diabetes and hyperlipidemia. β 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. β 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 β blockers that do not have ISA. Thus, in a large number of clinical situations in which hypertension is found, the properties of β 1 selectivity and ISA allow β blockers to be used with greater safety. Therefore, agents possessing both of these properties may be particularly valuable.