This type of medication quickly opens the airways by relaxing the bronchial muscles. Bronchodilators are the fastest-acting treatment for asthma attacks. Bronchodilators can be taken by mouth (in tablet or capsule form); however, inhaled sprays ("inhalers") are usually preferable because oral forms take longer to act and may also produce more side effects.
Bronchodilators can be used as a preventive measure before exposure to triggers known to cause asthma attacks, such as exercise or cold air. In addition to helping prevent an attack or reducing the severity of an attack that does occur, bronchodilators can improve a person's ability to tolerate such exposures.
The three types of bronchodilators are beta2 agonists, anticholinergics, and methylxanthine derivatives. These drugs all work to keep airways open, but each does so in a different way. A person with asthma may therefore need more than one type of bronchodilator.
Beta2 agonists. These are the most commonly used type of bronchodilator; they work the fastest and keep the airways open for many hours. The short-acting beta2 drugs—albuterol (Proventil, Ventolin) and levalbuterol (Xopenex)—begin to act in about 10 minutes and last for four to six hours. Long-acting beta2 agonists—salmeterol (Serevent)and formoterol (Foradil)—act within 15 to 30 minutes and continue to work for up to 12 hours. However, when used to treat asthma, these drugs must be used in combination with a controller medication to reduce the risk of serious, potentially fatal, adverse events.
Anticholinergics. If symptoms do not improve adequately, one option is to add either the anticholinergic ipratropium (Atrovent), which takes effect in 15 to 30 minutes and lasts four to six hours, or tiotropium powder inhaler (Spiriva HandiHaler), inhaling one capsule every 24 hours. Combivent and DuoNeb, which are combinations of the beta2 agonist albuterol and the anticholinergic ipratropium, also are available. It is important to bear in mind that, when used excessively, beta2 agonists can cause tremors and heart palpitations and can become less effective.
Methylxanthine derivatives. People who cannot tolerate beta2 agonists or anticholinergics or who experience asthma symptoms at night may benefit from one of the extended-release oral forms of the methylxanthine derivative theophylline (Theo-24, Uniphyl). Side effects of theophylline include nausea and insomnia.