Beta-agonists are used to relax the muscles that surround the bronchial airways. These muscles become constricted because of contact with irritants. Beta-agonists are made from adrenaline. This is a natural hormone which causes a rapid surge in energy when you are frightened, startled or excited. Inhaling the drug directly into the lung’s airways reduces the risk of side effects in the rest of the body.
Still, these inhaled medicines have side effects in some individuals even when taken as directed. Some of these are just annoying while others can be serious. Annoying side effects can include shaking, trembling, anxiety, nervousness, headache, insomnia, increased heart rate and dizziness. More severe side effects can include asthma attacks, chest pain and serious heart rhythm problems. Other serious side effects are changes in the electrical activity of the heart, low potassium and seizures. Fortunately, most patients on these medicines do
not have any of these problems.
The Duration of Beta-Agonists Varies from 1 to 24 Hours Depending on the Drug
Early treatments for lung disease relied on beta-agonists such as adrenaline. These were found to be quite effective. However, because their benefit was short-acting (less than an hour), scientists developed beta-agonists with longer and longer duration.
Rescue drugs, such as albuterol, have a quick onset of symptom relief. You may require a rescue bronchodilator from time to time. You may need one during periods of physical exertion. Or you may need one if you come in contact with high levels of irritants or pollutants. Albuterol starts working within 5 minutes, and lasts 4-6 hours.
The long-acting beta-agonists (LABAs) last for 12 hours or more. LABAs should never be used as rescue medicines. Using long-acting bronchodilators on a routine basis can help keep an open airway through the day and night. These have also been shown to reduce the number of exacerbations. It is expected that beta-agonists with durations in the 24-hour range will be coming soon.
Some recent studies suggest that LABAs may carry major risks for asthma patients. Therefore, guidelines suggest that LABAs only be given to asthma patients who continue to struggle after using inhaled corticosteroids. This LABA risk has not been seen in COPD.
Commonly Used Beta-Agonists
|U.S. trade name||Generic name||Inhaler (mcg)||Nebulizer (mg)||Duration of action|
|Short-acting Ventolin, Proventil, ProAir, Combivent||albuterol / salbutamol||100||2.5||3-6 hours|
|Long-Acting Servent, Advair||salmeterol salmeterol +||50|
|Foradil Perforomist Symbicort||formoterol formoterol +||12||0.02
|12 hours or more|
A mg (milligram) is 1,000 times greater than a mcg (microgram)