Asthma is a disease of the airways leading into the lungs. It is characterized both by narrowing of the airways, or bronchoconstriction, and inflammation of the lining of the airways. Successful treatment of asthma involves controlling both bronchoconstriction and inflammation. Because asthma is a very heterogeneous disease, meaning it can have very different effects in consequences from one person to the next, it is important that each patient is considered on an individual basis when it comes to selecting medications.
Types of Asthma Medications
According to "Clinical Immunology, Principles and Practice," asthma medications can be classified into two different categories. Asthma "relievers," act to provide immediate relief of an acute asthma attack. "Controllers," work to decrease the inflammatory processes that lead to asthma flares.
Relievers: Short-Acting Beta-Agonists
Short-acting beta-agonists, "SABAs," are the mainstay of treating acute asthma exacerbations. These medications work by attaching to beta-adrenergic receptors along the airways, causing the airways to dilate. SABAs are typically administered effectively by a nebulizer or an inhaler plus spacer. The most common side effects of SABAs are increased heart rate, headaches, irritability, and muscle tremors.
Relievers: Anticholinergics
Another group of reliever medications is called the anticholinergic agents. These agents block airway constriction caused by the action of acetylcholine on muscarinic nerve receptors. They are most helpful when used in combination with SABAs. The main side effect is mild dry mouth. This medication can be given either by nebulizer or inhaler.
Controllers: Inhaled Steroids
Inhaled corticosteroids, "ICS," are the most effective medication for preventing asthma symptoms. Any person with asthma who develops abnormal lung function when tested between asthma flares should have ICS added to their regimen. Having daytime symptoms more than twice a week or nighttime symptoms more than twice a month is also an indication to begin ICS therapy. The dose of ICS may need to be increased significantly to achieve asthma control, and at higher doses ICS can cause skin thinning, increased bruising, and even adrenal suppression. They are given by either dry powder or metered-dose inhalers.
Controllers: Long-Acting Beta-Agonists
Long-acting beta-agonists, "LABAs," like SABAs, help to decrease smooth muscle constriction in the airways. These medicines take longer to work and last for longer than the SABAs, however, so they are used as adjunctive medications to ICS rather than reliever medications. They have similar side effects to the SABA class.
Other Controller Medications
Leukotrienes are molecules that lead to airway narrowing, secretion of mucus into the airways, and increased inflammation in the airways. Leukotriene inhibitors have been shown to be most helpful in situations where asthma is poorly controlled despite maximal use of inhaled corticosteroids.
Another preventative medication is cromolyn sodium. Nedocromil is a similar medication. These agents work by inhibiting release of mast cell contents such as histamine, which may contribute to asthma. They have shown limited efficacy in reducing symptoms in small children, but did not prevent acute attacks and were not as effective as ICS.
Theophyllines are a class of mild bronchodilating medications with an unknown mechanisms of action. They may be helpful in severe asthma by decreasing the dose of ICS needed for symptom control. Their usefulness is limited by their side effects, which include nausea, vomiting, headaches, and, at high doses, seizures or death. This drug requires close monitoring by a physician.
References
- "Clinical Immunology: Principles and Practice"; Management of the Asthmatic Patient; Susana Marinho, M.D. and Adnan Custovic, M.D., Ph.D.; 2008.
- "Nelson's Pediatrics"; Chapter 143 Childhood Asthma; Andrew H. Liu et.al.; August 2007.
- "Pediatrics"; High-Dose Albuterol by Metered-Dose Inhaler Plus a Spacer Device Versus Nebulization in Preschool Children With Recurrent Wheezing: A Double-Blind, Randomized Equivalence Trial; Dominique Ploin et. al.; August 2000.
- "Pediatric Allergy, Principles and Practice"; Chapter 33 Guidelines for Treatment of Asthma; John O. Warner, M.D.; 2003.
