Beta blockers
Beta blockers
Definition
Beta blockers, also known as beta antagonists, are a class of drugs that were first developed for the treatment of certain heart conditions and hypertension. Later, beta blockers were also found to be useful in glaucoma, migraine, and some psychiatric disorders such as performance anxiety, tremors secondary to lithium, and movement disorders that are caused by some drugs used in the treatment of psychosis. There are a number of beta blockers approved for use in the United States, including acebutolol, bisoprolol, nadolol, proproanolol, and metoprolol, which have various trade names. Propranolol is the most commonly used in psychiatric practice.
Purpose
Beta blockers are proven effective in the treatment of performance anxiety, lithium-induced tremors, and neuroleptic-induced akathesia (a physical condition caused by certain antipsychotic drugs). Beta blockers have sometimes been used with benzodiazepines in treating alcohol withdrawal.
Description
Beta blockers act on that part of the central nervous system that controls mental alertness, lung function, heart rate, and blood vessels. Although there is more than one mechanism by which beta blockers work in anxiety states, the most beneficial result probably arises from the fact that beta blockers slow the heart to a normal rate and rhythm. Therefore, persons with performance anxiety do not experience the usual chest tightness and rapid heart rate that is associated with such acts as public speaking or acting.
Certain antipsychotic medications known as neuroleptics can cause an unwanted effect called akathesia, which is the inability to sit, stand still, or remain inactive. Patients are restless, and in severe cases, may pace constantly and forcefully and repeatedly stomp their feet. Beta blockers can sometimes treat this condition with a lower incidence of side effects than other drugs.
Recommended dosage
Propranolol is available in several different forms. Tablets are available, as are an oral solution and an injectable form. Dosage varies considerably depended on the reason for taking the drug and the age of the person. A physician will determine the appropriate dosage, although some examples are given below.
For one-time usage to treat performance anxiety, a single dose ranging from 10-40 mg taken a half hour before the performance (e.g., public speaking) is typical.
For lithium-induced tremors that cannot be controlled by reducing caffeine intake or administering the dosage of lithium at bedtime, propranolol at a dose of 20-160 mg daily can be given in two or three evenly divided doses.
For akathesia caused by antipsychotic medications, propranolol can be administered at doses of 10-30 mg three times daily.
Precautions
Because of their ability to narrow airways, beta blockers, especially propranolol, should not be taken by people with asthma and chronic obstructive pulmonary disease (COPD). If there is an urgent need to use beta blockers in persons with respiratory problems, atenolol or metoprolol are the beta blockers of choice because they are less likely to have this side effect, although even these drugs should also be used with caution. Patients with congestive heart failure, or certain cardiac conduction abnormalities such as a heart block, should also receive these drugs with caution.
Beta blockers should be used with close physician monitoring in people with diabetes, since the symptoms of low blood sugar (increased heart rate, light-headedness, and abnormal perspiration) may be not be recognized by patients.
KEY TERMS
Akathesia —Agitated or restless movement, usually affecting the legs. Movement is accompanied by a sense of discomfort and an inability to sit, stand still, or remain inactive for periods of time. Akathisia is a common side effect of some neuroleptic (antipsychotic) medications.
Benzodiazepines —A group of central nervous system depressants used to relieve anxiety or to induce sleep.
Tremor —Involuntary shaking of the hands and arms.
Side effects
Beta blockers can cause undesired decreases in blood pressure and are typically not given if blood pressure is 90/60 mm Hg or less.
Beta blockers can also cause an undesired drop in heart rate. People whose resting heart rate is less than 55 beats per minute should not take beta blockers.
Occasionally, beta blockers can cause rash, weakness, nausea, vomiting, and stomach discomfort.
Interactions
Each medication in the class of beta blockers has the potential to interact with a multitude of other medications. Anyone starting beta-blocker therapy should review the other medications they are taking with their physician and pharmacist for possible interactions. Patients should always inform all their healthcare providers, including dentists, that they are taking beta blockers.
Resources
BOOKS
Kaplan, Harold. Comprehensive Textbook of Psychiatry. Philadelphia: Lippincott Williams and Wilkins, 1995.
Kay, Jerald. Psychiatry: Behavioral Science and Clinical Essentials. Philadelphia: W. B. Saunders Company, 2000.
OTHER
National Library of Medicine. National Institutes of Health. “Beta-adrenergic Blocking Agents (systemic).” <http://www.nlm.nih.gov/medlineplus/druginfo/uspdi/202087.html>.
Ajna Hamidovic, Pharm.D.
Emily Jane Willingham, PhD