Beta blockers, in addition to their sympatholytic β1 activity in the heart, influence the renin–angiotensin system at the kidneys. Beta blockers cause a decrease in renin secretion, which in turn reduces the heart oxygen demand by lowering the extracellular volume and increasing the oxygen-carrying capacity of the blood. Heart failure characteristically involves increased catecholamine activity on the heart, which is responsible for several deleterious effects, including increased oxygen demand, propagation of inflammatory mediators, and abnormal cardiac tissue remodeling, all of which decrease the efficiency of cardiac contraction and contribute to the low ejection fraction. Beta blockers counter this inappropriately high sympathetic activity, eventually leading to an improved ejection fraction, despite an initial reduction in ejection fraction. Trials have shown beta blockers reduce the absolute risk of death by 4.5% over a 13-month period. In addition to reducing the risk of mortality, the numbers of hospital visits and hospitalizations were also reduced in the trials.Therapeutic administration of beta blockers for congestive heart failure ought to begin at very low doses (1/8 of target) with a gradual escalation of the dose. The heart of the patient must adjust to decreasing stimulation by catecholamines and find a new equilibrium at a lower adrenergic drive. Anxiety
Officially, beta blockers are not approved for anxiolytic use by the U.S. Food and Drug Administration. However, many controlled trials in the past 25 years indicate beta blockers are effective in anxiety disorders, though the mechanism of action is not known.
In 1964, James Black synthesized the first clinically significant beta blockers—propranolol and pronethalol; it revolutionized the medical management of angina pectoris and is considered by many to be one of the most important contributions to clinical medicine and pharmacology of the 20th century.For the treatment of primary hypertension, meta-analyses of studies which mostly used atenolol have shown that although beta blockers are more effective than placebo in preventing stroke and total cardiovascular events, they are not as effective as diuretics, medications inhibiting the renin–angiotensin system (e.g., ACE inhibitors), or calcium channel blockers. Medical uses
Large differences exist in the pharmacology of agents within the class, thus not all beta blockers are used for all indications listed below.