Cardioselective Beta Blocker Use in Patients With Asthma

Beta-Adrenergic Blockade

The ß blocker propranolol was introduced in the early 1960s and was shown to be effective in the treatment of angina pectoris, hypertension, cardiac arrhythmias, and thyrotoxicosis.[8,9] Beta blockers were also shown to improve survival for patients after myocardial infarction, even for those with decreased left ventricular function. When the beneficial effects of ß-blocker therapy in patients with congestive heart failure were demonstrated more than two decades ago, such an approach was deemed counterintuitive due to the intrinsic negative inotropic effect of these agents.[10] Over the years convincing evidence of a substantial mortality benefit has been demonstrated so that ß-blocker therapy, once considered heretical, is now the standard of care for the treatment of patients with congestive heart failure. Table I summarizes the mortality benefits that have been found with ß blockers.

Currently there are many different ß blockers available with different pharmacologic properties (Table II). Cardioselective ß blockers, or ß-1 blockers, have more than 20 times more affinity for ß-1 receptors than for ß-2 receptors, whereas nonselective ß blockers have equal affinity for both receptors.[1] Intrinsic sympathomimetic activity is present to varying degrees in some ß blockers, which may result in an attenuation of their ß-blocking effects. Other ß blockers are known to have additional properties, such as a-receptor blockade or vasodilatation.

When the nonselective ß blocker propranolol was first introduced, it was used in doses as high as 240-1600 mg/d and was generally well tolerated with acute and chronic use.[8] However, occasional adverse effects were reported, including bronchospasm, heart failure, fatigue, hypoglycemia, intermittent claudication, decreased libido, and depression.[8,11] The standard lists of contraindications to ß blockers we have today are based on these early case reports that were seen with high doses of nonselective ß blockers. Because of the proven mortality benefit of ß blockers, many of the relative or absolute contraindications traditionally listed for ß blockers, including impaired left ventricular function, peripheral vascular disease, diabetes mellitus, depression, impotence, and advanced age, have been questioned and disproved.[10,12-15]

Previous PageSection 3 of 5Cardiovasc Rev Rep 24(11):564-572, 2003. © 2003 Le Jacq Communications, Inc.
This is a part of article Cardioselective Beta Blocker Use in Patients With Asthma Taken from "Erectile Disfunction Treatment" Information Blog