Download - Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Chapter 76 Drugs for Asthma
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Asthma
Chronic inflammatory disorder of the airway Characteristic signs and symptoms
Sense of breathlessness Tightening of the chest Wheezing Dyspnea Cough
Cause: immune-mediated airway inflammation
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Pathophysiology
Symptoms of asthma result from a combination of inflammation and bronchoconstriction, so treatment must address both components
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Overview of Drugs for Asthma
Two main pharmacologic classes Anti-inflammatory agents
• Glucocorticoids (prednisone) Bronchodilators
• Beta2 agonists (albuterol)
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Inhalation Drug Therapy
Three obvious advantages Therapeutic effects are enhanced Systemic effects are minimized Relief of acute attacks is rapid
Three types Metered-dose inhalers (MDIs) Dry-powder inhalers (DPIs) Nebulizers
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Anti-Inflammatory Drugs
Foundation of asthma therapy Taken daily for long-term control Principal anti-inflammatory drugs are the
glucocorticoids
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Anti-Inflammatory Drugs: Glucocorticoids
Include budesonide and fluticasone Considered the most effective anti-asthma drugs
available Reduce bronchial hyperreactivity Also decrease airway mucus production and
increase the number of bronchial beta2 receptors as well as their responsiveness to beta2 agonists.
Usually administered by inhalation, but IV and oral are also options
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Anti-Inflammatory Drugs: Glucocorticoids
Mechanism of action = Suppress inflammation Decreased synthesis and release of inflammatory
mediators Decreased infiltration and activity of inflammatory
cells Decreased edema of the airway mucosa
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Anti-Inflammatory Drugs: Glucocorticoids
Adverse effects Minor when taken acutely Can be severe when used long-term (adrenal
suppression, osteoporosis, hyperglycemia, and others)
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Anti-Inflammatory Drugs: Leukotriene Modifiers
Suppress effects of leukotrienes Less effective than inhaled glucocorticoids Available agents
Zileuton (Zyflo) Zafirlukast (Accolate) Montelukast (Singulair)
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Anti-Inflammatory Drugs: Cromolyn
Used for prophylaxis, not for quick relief Suppresses inflammation; not a
bronchodilator Route—inhalation
Nebulizer MDI
Adverse effects Safest of all antiasthma medications Cough Bronchospasm
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Bronchodilators
Provide symptomatic relief but do not alter the underlying disease process (inflammation)
In almost all cases, patient taking a bronchodilator should also be taking a glucocorticoid for long-term suppression of inflammation
Principal bronchodilators are the beta2-adrenergic agonists
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Bronchodilators: Beta2-Adrenergic Agonists
Include albuterol, salmeterol, terbutaline Most effective drugs for relief of acute
bronchospasm and prevention of exercise-induced bronchospasm
Use in asthma: both quick relief and long-term control
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Bronchodilators: Beta2-Adrenergic Agonists
Adverse effects Inhaled preparations
• Systemic effects: tachycardia, angina, and tremor Oral preparations
• Excessive dosage: angina pectoris, tachydysrhythmias• Tremor
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Bronchodilators: Beta2-Adrenergic Agonists
Mechanism of action Activate beta2 receptors in smooth muscle of lung,
promoting bronchodilation and thereby relieving bronchospasm
Also suppress histamine release in lung and increase ciliary motility
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Bronchodilators: Methylxanthines
Theophylline Benefits derive primarily from bronchodilation Narrow therapeutic index Plasma level 10 to 20 mcg/mL Toxicity is related to theophylline levels
Other methylxanthines include aminophylline and dyphylline
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Glucocorticoid/LABA Combinations
Available combinations Fluticasone/salmeterol (Advair) Budesonide/formoterol (Symbicort)
Indicated for long-term maintenance in adults and children
Not recommended for initial therapy
LABA = long-acting beta2 agonist.
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Management of Chronic Asthma
Tests of lung function Forced expiratory volume in 1 second (FEV1) Forced vital capacity (FVC) Peak expiratory flow (PEF)
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Management of Chronic Asthma
Four classes of chronic asthma Intermittent Mild persistent Moderate persistent Severe persistent
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Management of Chronic Asthma
Treatment goals Reducing impairment Reducing risk
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Management of Chronic Asthma
Long-term drug therapy Agents for long-term control (eg, inhaled
glucocorticoids) Agents for quick relief of ongoing attack (eg,
inhaled SABAs)
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Management of Chronic Asthma
Stepwise therapy Step chosen for initial therapy is based on
pretreatment classification of asthma severity Moving up or down a step is based on ongoing
assessment of asthma control
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Management of Chronic Asthma
Important to reduce exposure to allergens and triggers
Sources of allergens: house dust mites, pets, cockroaches, mold
Factors that can exacerbate asthma: tobacco smoke, wood smoke, household sprays
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Drugs for Acute Severe Exacerbations
Requires immediate attention Goal is to relieve airway obstruction and
hypoxemia, and normalize lung function as quickly as possible.
Initial therapy consists of• Giving oxygen to relieve hypoxemia• Giving a systemic glucocorticoid to reduce airway
inflammation• Giving a nebulized high-dose SABA to relieve airflow
obstruction• Giving nebulized ipratropium to further reduce airflow
obstruction.
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Reducing Exposure to Allergens and Triggers
Measures to control or avoid dust mites and their feces include Encasing the patient’s pillow, mattress, and box
spring with covers that are impermeable to allergens
Washing all bedding and stuffed animals weekly in a hot-water wash cycle (130 °F)
Removing carpeting or rugs from the bedroom Avoiding sleeping or lying on upholstered furniture Keeping indoor humidity below 50%