A Look At Beta Blockers

By Michael D. Shaw June 19, 2017

 

Beta-adrenoceptor antagonists—aka beta blockers—are drugs that bind to beta-adrenoceptors and thereby block the binding of norepinephrine and epinephrine to these receptors. Epinephrine, more familiarly known as “adrenaline,” increases cardiac output, and raises blood glucose levels. The hormone is released during periods of stress, as part of the “fight or flight” response. Among other things, the heart rate and blood pressure will increase.

Norepinephrine, in contrast with epinephrine (produced and stored primarily in the adrenal glands), is mostly stored and released in the neurons of the sympathetic nervous system—with a small presence in adrenal tissue. As such, norepinephrine is best thought of as a neurotransmitter, with some functionality as a hormone.

For those keeping score at home, there are three types of beta receptors, known—oddly enough—as beta₁, beta₂, and beta₃. For this article, we are primarily concerned with beta₁ (as found in the heart) and beta₂ (as found in vascular smooth muscle).

First generation beta blockers (propranolol et al.) are non-selective, and will block both beta₁ and beta₂ receptors, affecting numerous organs and muscle tissues. Second generation drugs (metoprolol et al.) block only beta₁ receptors, affecting mostly the heart.

If you’re wondering about that other stress hormone—cortisol—the use of pharmaceutical drugs to lower its release, in the absence of disease, is a lot more dicey. On the other hand, natural solutions, such as eliminating caffeine, are readily available.

Simply put, beta blockers cause the heart to beat more slowly and with less force, thereby reducing blood pressure. In addition, beta blockers dilate blood vessels, to improve blood flow. More than that, they have an anti-stress/anxiolytic effect. As such, they have long been recommended for stage fright.
The linked NY Times piece has a number of interesting takes on the matter…

“Before propranolol, I saw a lot of musicians using alcohol or Valium,” said Mitchell Kahn, director of the Miller Health Care Institute for the Performing Arts, describing 25 years of work with the Metropolitan Opera orchestra and other groups. “I believe beta blockers are far more beneficial than deleterious and have no qualms about prescribing them.”

“If you have to take a drug to do your job, then go get another job,” said Sara Sant’Ambrogio, who plays cello in the Eroica Trio. And, some observers claim that chemically-assisted performances can be “soulless and inauthentic.”

Beyond the anxiety and hypertension indications, beta blockers are used to treat angina pectoris, cardiac arrythmias, glaucoma, migraine headaches, and certain types of tremors. Several beta blockers are included in the WHO Model List of Essential Medicines. A further honor is that one of the recipients of the Nobel Prize in Physiology or Medicine for 1988 was the late Sir James W. Black. Note that the Nobel is seldom awarded in conjunction with a specific pharmaceutical therapy.
Black “realized the great pharmaco-therapeutic potential of receptor-blocking drugs and developed in 1964 the first clinically useful beta-receptor-blocking drug, propranolol. This type of drug is now being used in the treatment of coronary heart disease (angina pectoris, myocardial infarction) and hypertension.”

Here is a listing of side effects for beta blockers (many people who take beta blockers won’t have any side effects):

Common

• Fatigue
• Cold hands or feet
• Weight gain

Less Common

• Shortness of breath
• Trouble sleeping
• Depression

Special notes apply to asthmatics, in that beta blockers may trigger attacks. For diabetics, owing to the effect of lowering the heart rate, hypoglycemia (which can increase the heart rate) may be hidden.
This column takes its shots at Big Pharma, but this time salutes the industry for such products as beta blockers.