Asthma: Diagnosis and Management ____________________________________________________________
Epinephrine The first oral medication to become available for the relief of an acute asthma episode was epinephrine, a hormone produced by the sympathetic nervous system. Epinephrine was once the first choice for treating acute asthma, but it has proved to be a weak bronchodilator with quickly diminished action. Moreover, epinephrine has very potent systemic effects, causing tachycardia, high blood pressure, nervousness, headache, and in some cases, panic attacks. However, this medication may still be used intravenously or subcutaneously in severe asthma emergencies. Epinephrine can be described as nonselective; that is, the medication acts on both the lungs and the heart [9; 13]. Despite its limitations, epinephrine remains the treatment of choice for severe asthma and airway constriction related to allergy. There is agreement that self-injectable epinephrine should be prescribed for patients who have had a previous allergic reaction involving the respiratory or cardiovascular system. The patient, as well as caregivers and all members of the family, should be instructed in how to administer the injection. Parents of children who have been prescribed self- injectable epinephrine should inform school personnel about the allergy and the availability of the medication. Instructions regarding the proper use of self-injectable epinephrine should be repeated frequently to ensure proper use during emergency situations [9; 31]. Beta 2 Agonists Bronchodilators that selectively act on the lungs have largely replaced the routine use of epinephrine. These drugs are called beta 2 agonists. Beta 2 agonists stimulate the sympathetic nervous system, similar to epinephrine. However, they only act on receptors located in nerve endings inside the lungs. These medications provoke specific beta 2 receptors in the muscles encasing the bronchial tubes to reverse; when the drug stimulates these receptors, bronchial muscles relax and bronchial tubes dilate. Beta 2 agonists last longer in the body than epinephrine and result in less risk of cardiovascular side effects, making them the drugs of choice for safe, short-acting bronchodilation [9; 11; 35]. Beta 2 agonists may cause negative side effects, especially if fast- acting forms are taken too frequently for too long. Overuse can lead to poor asthma control and possibly desensitization. Inhaling more than one canister a month indicates an excessive reliance on bronchodilators to improve asthma. Patients with severe asthma may prefer a beta 2 agonist for quicker action than anti-inflammatory medications, which take days to act. However, patients may then expose themselves to potentially fatal attacks due to decreased beta 2 agonist effectiveness if the asthma flares out of control [9; 11].
equals two sprays of medication (although double doses are available). One disadvantage of the dry powder is the amount of coordination needed to load the capsule into some inhalers. This can be a problem for the young or elderly or for people with arthritis, Parkinson disease, or other diseases affecting coordination or dexterity. Furthermore, depending upon the patient’s ability to breathe in deeply, variable amounts of medication may be inhaled. Another concern involves the effect of humidity on dry powder, which may influence dose strength [9; 11]. The nebulizer is a form of inhaler that acts as a vaporizer or humidifier, delivering microdroplets of asthma medication in spray form and allowing a patient to breathe it in through a mouthpiece or face mask. Larger doses from nebulizers may increase the risk of side effects, and studies have shown MDIs to be as effective as nebulizers in delivering medication to the lungs. Nebulizers are used frequently in children as they are easier to administer and provide more accurate dosing. In the past, hospitals frequently provided medication in nebulizers to treat emergency asthma episodes, but now many facilities have converted to the use of MDIs [9; 11]. Oral Administration In addition to inhalers, many asthma medications are manu- factured as pills, granules, or liquids to be ingested orally. Oral medications benefit patients by reaching the small bronchial tubes that most inhaled medication cannot reach. Newer developments in longer-acting, timed-release oral medications adapt to the needs and lifestyles of many patients. However, the amount of medication absorbed over a given time period can vary. Some medications may take up to six times longer than others to reach peak concentrations, which means each patient may require a different dose and frequency of administration to reverse breathing problems [11; 13]. The disadvantage associated with oral medications is the sys- temic distribution. If negative or unpleasant side effects occur, they last the entire time the medication is active in the body. Depending upon the form and dose, oral medication may be more difficult for the system to balance throughout a 12- or 24-hour period than inhaled formulations [11; 13]. Bronchodilators Bronchodilators are used to address the acute symptoms of an asthma attack. They act by relaxing the muscles surround- ing airways, thereby dilating bronchial tubes. The primary categories of bronchodilators are beta 2 agonists, theophylline derivatives, and anticholinergics. Most often, bronchodila- tors are prescribed in inhaler or aerosol form. They are also available in liquid, tablet, and capsule forms, but these are generally not used due to gastrointestinal side effects. The bronchodilator inhaler is usually the first line of defense in an asthma attack [11; 13].
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MDVT1726
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