Julian Frieden

Present state of alpha- and beta-adrenergic drugs I. The adrenergic receptor.

The cardiovascular alpha adrenergic receptors evoke vasoconstriction, the cardiovascular beta receptors evoke vasodilation and cardiac stimulation. All blood vessels have both alpha and beta receptors. In some areas, for example skin and kidney, the alpha receptors predominate. In some vascular beds, for example the nutrient vessels in skeletal muscle, beta receptors predominate. In other beds, such as coronary, visceral, and connective tissue both receptors are active. The cardiovascular effects of adrenergic agonists depend on which receptor they act on. Phenylephrine is specific for alpha receptors. Isoproterenol is specific for beta receptors. Epinephrine and norepinephrine act on both. The real value of knowing the receptor specificity of each agonist is that side effects can more easily be predicted. For example, adrenergic cardiac stimulants are antiasthmatics. Therefore, adrenergic antiasthmatics can produce excessive cardiac stimulation. For the future, agonists that are not only receptor-specific but also tissue-specific will be developed. The first of these in the United States is terbutaline. The rest of the world has in addition a similar drug, salbutamol. No one knows if this drug will be approved for use by American physicians.

Present state of alpha and beta adrenergic drugs. II. The adrenergic blocking agents.

There are selective blocking agents (antagonists) for alpha receptors and beta receptors. These blocking agents prevent the response to injected agonists and neurogenically released norepinephrine. The principal cardiovascular response to alpha blockade is postural hypotension with reflexly induced cardiac stimulation. If neurogenic vasoconstriction is present, this will be removed. The principal cardiovascular response to beta blockade is bradycardia. If fast arrhythmias are present, these will be slowed. Beta blockade tends to increase peripheral resistance. Unless circulation is previously impaired this vasoconstrictive effect is insignificant.

Present state of alpha and beta adrenergic drugs III. Beta blocking agents

The beta blocking agents are valuable drugs in cardiology. They are effective in any fast arrhythmia. Together with nitroglycerin, beta blockers are drugs of first choice in angina. As antihypertensives, they have advantages that should make them drugs of first choice. For migraine the beta blockers are equal to any other type of drug. With more study their place in treating anxiety will be clarified. And without question other uses will be found. It is difficult for this author to understand the attitude of the FDA to this class of drugs. To limit the American physician to only one drug in this large group of drugs is unheard of. Although it can be argued that propranolol is the best one, there are obvious cases where another drug would be better. For example, propranolol induces nightmares in a few patients. There is evidence to show that timolol does this less frequently. FDA delay in approval of propranolol for essential hypertension is totally incomprehensible. Other approved drugs are less effective and much more toxic. Propranolol, and the other beta blockers, are safe and effective. The adverse beta effects are easily controlled or avoided. The other adverse effects are no more frequent than with any other class of drugs, and all are reversible. It is to be hoped that science and common sense will prevail over bureaucratic indecision.

Atropine in the treatment of cardiac disease

Abstract Atropine is useful in treating acutely ill patients when bradycardia is associated with a low cardiac output or ventricular irritability. Proper administration may avert the need for pacemaker, isoproterenol, or lidocaine therapy. The drug may also be of diagnostic aid in specific cardiac conditions.