Treatment of Asthma - Part I
by Warren P. Silberstein, M.D.
The main categories of medications used to treat asthma are anti-inflammatory drugs, since asthma is an inflammatory disease of the airways, and bronchodilators which help to relieve the constriction of the airways which cause the acute symptoms of asthma. In the management of asthma these medications are divided into maintenance drugs - those medicines which are taken chronically to control and prevent asthma symptoms, and rescue drugs - those medications which are used to relieve acute symptoms.
All of the rescue medications are rapidly acting bronchodilators, drugs which reduce the constriction of the smooth muscles of the bronchial tree quickly thereby opening the airways and providing almost immediate symptomatic relief of wheezing. The main differences between them are the degree of cardiac (heart) stimulation, duration of action, and the mode of administration. This list reviews the major medications in use today in the U.S.A. but is by no means a complete listing of all rescue medications. The main rescue medications in other countries may differ, but the principles are the same. For mild asthmatics who have only occasional symptoms treatment with rescue medications may be sufficient, but since these medications do not reduce the inflammation that causes the airway constriction or the increased mucus production, asthmatics who have more frequent, persistent, or severe symptoms require maintenance medications as well.
- Albuterol (Proventil, Ventolin) - available as a syrup, tablet, spray, and nebulizer solution. These medications work by stimulating receptors on the smooth muscles lining the bronchial tree causing these muscles to relax. Syrup and tablets must be absorbed into the system before they can reach the place where they work. Sprays are much more effective at relieving acute symptoms because when they are inhaled they go right to where they are needed and begin to work immediately. Because the medication is going directly to where it is needed less medication needs to enter the body to get results than with pills or syrup. The use of sprays may be limited in children because of the need to learn the skills necessary for proper inhalation of the medication. There are devices (spacers) which can aid in the delivery of sprays. The effectiveness of sprays may also be limited by an asthmatic's ability to hold the spray in his lungs if he is coughing too much and the inability of the spray to get down into the small airways during a severe asthma attack. A nebulizer delivers the medication on a fine mist over a period of 10 to 15 minutes. This makes it more suitable for use with infants because there are no skills to learn in order for the infant to inhale the medication. The nebulizer is also more effective for treating acute attacks than the spray. Inhalations (nebulizer and spray) provide 4 to 6 hours of bronchodilation and may be repeated every 4 hours as necessary; however, patients who require frequent or prolonged treatment with rescue medications also require maintenance medications for better control and prevention of symptoms. We will talk more about spacers, nebulizers, and the proper use of these medications in the next two weeks when we talk about the Management of Asthma.
The main side effects of albuterol are a result of its stimulant properties. It can cause rapid heart rate, palpitations, tremors, shakiness, nervousness, hyperactivity, irritability, and insomnia. Surprisingly, any inhaled medication including bronchodilators like albuterol can provoke wheezing by irritating the airways.
- Metaproterenol (Alupent, Metaprel) - available as a syrup, tablet, spray, and nebulizer solution. The mechanism of action and side effects are the same as albuterol. Patients who experience excessive side effects from one of these medications may tolerate the other.
- Pirbuterol (Maxair) - available as a spray. Similar to albuterol and metaproterenol.
- Terbutaline (Brethaire, Brethine, Bricanyl) - available as spray, tablets, and injection. Similar to all above. The injectable form can be used to relieve bronchospasm in emergency situations.
- Isoetharine (Bronkosol, Bronkometer) - available as spray and nebulizer solution. The mechanism of action and side effects are similar to all of the above; however, isoetherine is more cardiac stimulant than the newer medications previously discussed. In addition, its duration of action is not as prolonged but its frequency of use is limited by its side effects. Some severe chronic asthmatics may respond better to isoetharine than the other medications.
- Isoproterenol (Isuprel) - available as spray, tablets, and nebulizer solution - Similar to isoetharine. Isoproterenol is a potent bronchodilator which may be used intravenously with careful monitoring in extreme situations.
- Epinephrine bitartrate (Primatene) - available as a spray (Primatene tablets are a different formulation). The mechanism of action is similar to all the sprays above. Like isoetharine, it is more cardiac stimulant and does not have as prolonged bronchodilator effect as albuterol and similar sprays. Primatene is a popular medication because it provides rapid relief of symptoms, is available without a prescription, and has been advertised on TV for years. I think asthmatics would be better served by having their care supervised by a physician and using the newer prescription sprays which provide more prolonged relief with fewer side effects. In addition, as we will discuss in the next two weeks when we talk about the Management of Asthma, rescue medications are sufficient treatment for asthmatics who have only occasional symptoms, but patients with severe, chronic, or recurrent symptoms require appropriate maintenance medications which are only available through a physician.
- Epinephrine or Adrenaline - two names for the same thing. Available as an injectable. the mechanism of action and side effects are similar to isoetharine and isoproterenol. The advantage of injectables is that they can be used to provide quick relief to asthmatics who are having such severe bronchospasm that inhalation is not effective. Epinephrine is available in an auto-injector (Epi-pen and Epi-pen Jr.) which can be used for self administration for acute allergic reactions and acute asthma. Such use is intended to relieve acute symptoms to allow time to seek medical care and is not a substitute for such care.
Next article in series: Maintenance Medicines
For more information about asthma medications check the following Web sites:
Asthma Medications for Kids - brought to you by the American Lung Association
With summer coming you might also want to check the information from the American Lung Association about Asthma Camps and Summer Camp Tips For Children With Asthma.
Asthma Tutorial - Bronchodilators