Chronic Obstructive Pulmonary Disease (COPD) (cont.)

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Beta-agonists

Historically, one of the first medications used for asthma was adrenaline (epinephrine). Adrenaline has a rapid onset of action in opening the airways. It is still used in certain emergency situations for attacks of asthma. Unfortunately, adrenaline has many side effects including rapid heart rate, headache, nausea, vomiting, restlessness, and a sense of panic. Therefore, it is not used in the treatment of COPD.

Beta-2 agonists have the bronchodilating effects of adrenaline without many of its unwanted side effects. Beta-2 agonists can be administered by MDI inhalers or orally. They are called "agonists" because they activate the beta-2 receptor on the muscles surrounding the airways. Activation of beta-2 receptors relaxes the muscles surrounding the airways and opens the airways. Dilating airways helps to relieve the symptoms of dyspnea (shortness of breath). Beta-2 agonists have been shown to relieve dyspnea in many COPD patients, even among those without demonstrable reversibility in airway obstruction. The action of beta-2 agonists starts within minutes after inhalation and lasts for about 4 hours. Because of their quick onset of action, beta-2 agonists are especially helpful for patients who are acutely short of breath.

Because of their short duration of action, these medications should be used for symptoms as they develop rather than as maintenance. Evidence suggests that when these drugs are used routinely, their effectiveness is diminished. These are referred to as rescue inhalers.

Examples of beta-2 agonists include albuterol (Ventolin HFA, Proventil HFA, Proair), metaproterenol (Alupent), pirbuterol (Maxair), terbutaline (Brethaire), isoetharine (Bronkosol), and levalbuterol (Xopenex). Albuterol is a chemical that comes mixed in two forms, mirror images of itself, a left and right hand. Levalbuterol is a purer form of albuterol, the left hand component. There are some theoretical advantages to this form including possibly reduced side effects.

Side effects of beta-2 agonists include anxiety, tremor, palpitations or fast heart rate, and low blood potassium (hypokalemia).

Medically Reviewed by a Doctor on 5/13/2013

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