Beta-agonist: A bronchodilator medicine that opens the airways by relaxing the muscles around the airways that may tighten during an asthma attack or in COPD (chronic obstructive pulmonary disease). Beta-agonists can be administered by inhalers or orally. They are called “agonists” because they activate the beta-2 receptor on the muscles surrounding the airways. Activation of beta-2 receptors relaxes the muscles surrounding the airways and opens the airways. Dilating airways helps to relieve the symptoms of dyspnea (shortness of breath). Beta-2 agonists have been shown to relieve dyspnea in many asthma and COPD patients. The action of beta-2 agonists starts within minutes after inhalation and lasts for about 4 hours. Because of their quick onset of action, beta-2 agonists are especially helpful for patients who are acutely short of breath but, because of their short duration of action, several doses of beta-agonists are often necessary each day. The side effects of beta-2 agonists include anxiety, tremor, palpitations or fast heart rate, and low blood potassium.
Examples of beta-2 agonists include albuterol (Ventolin, Proventil), metaproterenol (Alupent), pirbuterol (Maxair), terbutaline (Brethaire), isoetharine (Bronkosol), and Levalbuterol (Xopenex). Beta-2 agonists with a slower onset of action but a longer period of activity such as salmeterol xinafoate (Serevent) are now available. Salmeterol has a duration of action of twelve hours and need only be taken twice a day.
Beta-secretase: An enzyme that appears to be directly involved in the early development of Alzheimer’s disease. Beta-secretase is a protease (an enzyme that catalyses the splitting of interior peptide bonds in a protein). Beta-secretase acts by trimming off a protein protruding from a brain cell. This small snip is thought to be the first step […]
- Betel nut
Betel nut: The nut of the Areca palm tree and an ingredient of betel nut quid, an addictive mix chewed in some Pacific and Asian cultures. Its use is associated with aggressive oral cancers affecting especially the inner lining of the cheeks and lips are the primary tumor sites. Other sites include the tongue, lower […]
- Beverly Hills diet
Beverly Hills diet: The Beverly Hills diet is a weight loss plan based upon the premise that eating certain fruits leads to chemical reactions in the body that enhance weight loss. Only fruit is consumed for the first period (usually 10 days) on this diet, and then carbohydrates (on day 11) and protein (on day […]
Bezoar: A clump or wad of swallowed food or hair. Bezoars can block the digestive system, especially the exit of the stomach. A bezoar composed of hair is called a trichobezoar. A bezoar composed of vegetable materials is called a phytobezoar. A bezoar composed of hair and food is called a trichophytobezoar.
BCG: An effective immunization against tuberculosis. BCG stands for Bacille Calmette Guerin. BCG is a weakened (attenuated) version of a bacteria called Mycobacterium bovis which is closely related to Mycobacterium tuberculosis, the agent responsible for tuberculosis. Camille Guerin (1872-1961) and Albert Calmette (1863-1933) produced the BCG strain of the bacteria at the Pasteur Institute in […]