Asthma is caused by inflammation of the airways (windpipes). This inflammation triggers bronchospasm, or contraction of the muscles which line the airways. The inflammation can also trigger swelling and mucus production. These phenomena (bronchospasm, swelling, and mucus production) all contribute to narrowing of the airways which causes wheezing and shortness of breath as it becomes harder and harder to get air out of the lungs. For most patients, getting air into the lungs is not nearly as difficult as getting out of the lungs.
A number of medications are available to treat asthma and some of these medications have their main effect on bronchospasm whereas others have their main effect on inflammation, swelling, and mucus production. Although some patients with milder asthma may require only one drug from one of these classes, patients with moderate or severe asthma generally require more than one drug from more than one class.
There are three types of medications which have their main effect on bronchospasm: the methylxanthines, beta agonists, and anticholinergics.
The methylxanthines include drugs such as theophylline (a pill form) and aminophylline (an intravenous form). These drugs are structurally somewhat similar to caffeine and can have similar side effects including jitteriness and a sensation that the heart is racing. These drugs are fairly weak bronchodilators, that is they have only a mild effect on relieving bronchospasm. The long acting pill forms of theophylline (such as Theo-Dur, Slo-Bid, or Uniphyl) are most commonly prescribed for asthma. Methylxanthines have become less popular for asthma as newer and more powerful bronchodilators have been developed.
The main category of bronchodilators is the beta agonists. These drugs can be given by inhalation, pill, or injection. In general, when asthma drugs can be given by inhalation, they are less likely to have side effects on the other parts of the body (such as jitteriness or palpitations). However, some patients find using inhalers extremely difficult and therefore prefer the pill forms of some of these drugs. When given by inhalation, beta agonists can be given by a metered dose inhaler or by a nebulizer. The most common beta agonist is albuterol which is available generically (least expensive) or under the brand names Proventil and Ventolin. Albuterol is available by nebulizer, metered dose inhaler, and pill. Other beta agonists which are given by inhalation include pirbuterol (Maxair), metaproterenol (Metaprel), terbutaline (Breath Air), and bitolterol mesylate (Tornalate). Primatene mist contains epinephrine which is an older medication that is more likely to have side effects than albuterol or other beta agonists and is generally is not recommended for most patients with asthma. The beta agonists all differ in terms of their likelihood of causing side effects on the heart (such as palpitations or abnormally fast heart rhythms). A long acting beta agonist, Salmeterol (Serevent) and fometerol (Foradil), have an advantage of lasting up to 12 hours whereas the other beta agonists generally last only 3 to 6 hours; however, salmeterol has been linked to higher death rates when used without a steroid inhaler.
The third type of bronchodilator is the anticholinergic group of which only ipratropium (Atrovent) and tiotropium (Spiriva) are currently commercially available. They act differently from the beta agonists and can be given along with them. In general, anticholinergics seem to be more effective than beta agonists for patients with emphysema and chronic bronchitis but the beta agonists appear to be more effective in patients with asthma. There can be a tremendous amount of individual variation, however, and it is often difficult to predict which drug is preferable in any given patient. A combined preparation, Combivent, contains both albuterol and Atrovent.
Within the category of drugs which cause reduction in inflammation and mucus production, there are a number of medications including steroids, leukotriene inhibitors, and cromolyn/nedocromil.
Steroids are the most powerful inflammation inhibitors and are available by the inhaled route (see Web file on inhaled steroids), the oral route (see Web file on taking oral corticosteroids), and the intravenous route. As with the beta agonists, side effects can be minimized by taking these drugs by inhalation so that the medicine gets only to the lungs where it is needed. Often by taking the inhaled steroids, patients will have a reduction in their bronchospasm and will need fewer bronchodilator medications. Similarly, if you are taking very frequent bronchodilators ( more than four times per day) that is a sign that you need more medicine to reduce the inflammation which is driving the bronchospasm. Inhaled steroids are marketed as the steroid alone or in combination with a long acting beta agonist.
The leukotriene inhibitors are the newest group of drugs to reduce inflammation and are available in pill forms (Zyflo, Accolate, and Singulair). These drugs inhibit leukotrienes which are one component of inflammation that causes asthma. These drugs will work in approximately three-quarters of patients with asthma but will no have effect in approximately one-quarter. These medications have very few side effects and can often allow a patient to discontinue other asthma medications, including inhaled steroids. For other patients, a reduction in the amount of inhaled steroids necessary to control inflammation can be achieved. Since the leukotriene inhibitors are only available by pill form, some patients find this to be easier to use than the inhaled steroids.
The third group of drugs used to control inflammation includes cromolyn (Intal) and nedocromil (Tilade). These drugs are given by inhalation and are generally less powerful than the inhaled steroids. They are most likely to work in younger patients, such as children and adolescents. However, some adults can have quite good responses to Intal or Tilade. These have the advantage of almost no side effects in most cases.
These drugs are combined in a four step approach to managing asthma, depending on the individual patient's severity. For patients with mild/intermittent asthma, a short acting beta agonist (such as albuterol) is generally the only medication necessary. This is used on an as needed basis for quick relief rather than on a scheduled basis in this group of patients.
For patients with mild/persistent asthma, step 2 medications are employed which consists of an antiinflammatory drug. In adults, this is usually an inhaled low dose corticosteroid. Alternative drugs for patients who are not able to tolerate inhaled corticosteroids include either a leukotriene inhibitor,or cromolyn/nedocromil. A short acting beta agonist, is still used on an as needed basis.
For patients with moderate/persistent asthma, step 3 medications are employed. This consists of an inhaled corticosteroid and a long acting bronchodilator (either inhaled Servent, a long acting beta agonist tablet, or a long acting theophylline compound). The short acting beta agonists are continued to be used on an as needed basis.
For patients with the most difficult asthma, those with severe/persistent symptoms, step 4 medications are employed. This consists of the inhaled corticosteroids, the long acting bronchodilators, and oral corticosteroids. Short acting beta agonists are continued to be used on an as needed basis.
All patients requiring Step 2, 3, or 4 medications should have asthma education (as can be provided by programs such as the comprehensive asthma clinic at the Ohio State University Medical Center and such as the American Lung Association). Additionally, patients with asthma of this severity should have a home peak flow meter to assist in their asthma management (see Web file on using your peak flow meter). All patients with asthma should take measures to control environmental conditions which can trigger their asthma (see Web file on environmental control of asthma).
Asthma is very common and at sometime will affect nearly 15% of the American population. Fortunately, for most patients, asthma is mild but in some patients, asthma can be much more severe and even life threatening. With proper care, your asthma can be controlled and permit you to have unrestricted physical activities and freedom from daily symptoms.
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