How Asthma Medicines Work
Bronchodilators quickly help “open” up the constricted bronchial passages, giving the person a sense of relief. Albuterol, Xopenex, Ventolin and Proventil are all bronchodilators. They are commonly given with an metered dose inhaler, or a nebulizer. They can also be given as oral or intravenous forms. Theophylline and Alupent are examples of oral bronchodilators.
Bronchodilators can make people feel a little “racy” or “hyper”–like a strong cup of coffee. It is very important that people with asthma don’t overuse bronchodilators. Because of their effect on the autonomic nervous system, if excessive doses are given, a person can feel as though they’re “speeding” and the heart can be overstimulated, causing arrhythmias. While taking bronchodilators, a person should avoid excessive caffeine and over-the-counter decongestants that contain pseudoephedrine . When an asthmatic person has strong hay fever symptoms, he or she can take antihistamines or decongestants, but some antihistamines are more compatible with asthma needs than others (example: plain benadryl or the prescription antihistamine Zyrtec, instead of an over-the-counter combination product.)
An inhaler should not be used more than every four hours. Also, if a person feels as though they’re tightening up from an air irritant such as cigarette smoke at a party, it’s very important for them to get away from the irritant–otherwise they’re just opening up their bronchial tree more and breathing in even more of the triggering substance. This can cause the asthma attack to snowball. Still feeling tight after using the bronchodilator means the asthmatic has to add on another medicine, an anti-inflammatory.
This class of medicine helps “calm” the storm that’s beginning to brew. In response to a viral infection or allergen, an array of immune cells (T cells, macrophages, eosinophils, basophils, etc) are “called into action” along the bronchial lining. They cause the release of histamine and other inflammatory substances that flood the mucous membranes. It is thought that asthmatic people have a different profile of T cells and other immune response cells that leads to a more exaggerated response. Their bronchial passages become swollen, boggy, plus constricted as underlying smooth muscles tighten up. The immune cells send out a bugle call for even response cells, that leads to even more congestion.
Steroids have their calming effect by suppressing some branches of the immune response. When given early in an asthma attack, they can prevent the attack from escalating. They also help prevent microscopic scar formation along the respiratory lining. Inflammation can cause a component of the lining, called the basement membrane, to become thickened. This phenomena is called airway remodeling and can cause decreased lung function in the future. It also sets the stage for more airway compromise during asthma attacks in the future. Why airway remodeling occurs more in some people than others is unknown. However, it is thought that including inhaled steroids in the treatment of young children with asthma makes it more likely that they will outgrow their asthma, or have less severe forms of the disease.
Parents often worry that inhaled steroids have side effects. High dose steroids do have a wide array of possible uses (delayed growth, cataracts, immunodeficiency). However, the inhaled forms used for asthmatic purposes are a small fraction of the doses used for autoimmune and other diseases. They have been used safely on asthmatic children in many countries for many years. When used in the context of asthma, the benefits far outweigh the risks. After a child has an asthma attack, immune response cells can remain along the lining for weeks. If the child gets another cough/cold, those cells can be rapidly activated – causing another asthma attack. That’s why inhaled steroids are usually continued for weeks after an episode, and for some children, through the winter.
This is a new class of medicines that address one of the players in the cascade of events that underly an asthma attack. Leukotriene modifiers block the actions of a substance, Leukotriene B4, which is part of what is called the late phase response. Like histamine, it promotes bronchial congestion and wheezing several days after the asthma kicked in. Like the preventative medicines (Intal), leukotriene inhibitors (Accolate, Singulair) are used on a day-to-day basis as a preventative measure during periods of the year when a person’s asthma is very active. For people with few episodes who don’t feel the need for long-term medicines, the leukotriene inhibitors can be helpful in the 10 days after an attack starts. It is during this time that the bronchial tree is more “jumpy” and easily irritated.
This class of medicines decreases the release of histamine along the bronchial tree. When an allergen or vital infection irritates the bronchial tree, cells called eosinophils are activated. They release microscopic packets of histamine. This histamine causes swelling, congestion, and a flood of mucous. Intal works by tightening the cell membranes of the eosinophils, making it harder for the histamine to be released. Should the person be exposed to an allergen or viral infection, the asthma episode can be less intense. A commonly used histamine stabilizer is called Intal. It doesn’t have an immediate effect and it takes a couple of weeks for the eosinophil membranes to be tightened. Intal is a preventive medicine, and taken on a day-to-day basis thoughout the allergy season or through the fall/winter season when colds and coughs prevail.