Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Chapter 76 Drugs for Asthma.

Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc.

Chapter 76

Drugs for Asthma

Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 2

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


Pathophysiology

Symptoms of asthma result from a combination of inflammation and bronchoconstriction, so treatment must address both components


Overview of Drugs for Asthma

Two main pharmacologic classes Anti-inflammatory agents

• Glucocorticoids (prednisone) Bronchodilators

• Beta2 agonists (albuterol)


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


Anti-Inflammatory Drugs

Foundation of asthma therapy Taken daily for long-term control Principal anti-inflammatory drugs are the

glucocorticoids


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



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



Adverse effects Minor when taken acutely Can be severe when used long-term (adrenal

suppression, osteoporosis, hyperglycemia, and others)


Anti-Inflammatory Drugs: Leukotriene Modifiers

Suppress effects of leukotrienes Less effective than inhaled glucocorticoids Available agents

Zileuton (Zyflo) Zafirlukast (Accolate) Montelukast (Singulair)


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


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


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



Adverse effects Inhaled preparations

• Systemic effects: tachycardia, angina, and tremor Oral preparations

• Excessive dosage: angina pectoris, tachydysrhythmias• Tremor



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


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


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.


Management of Chronic Asthma

Tests of lung function Forced expiratory volume in 1 second (FEV1) Forced vital capacity (FVC) Peak expiratory flow (PEF)



Four classes of chronic asthma Intermittent Mild persistent Moderate persistent Severe persistent



Treatment goals Reducing impairment Reducing risk



Long-term drug therapy Agents for long-term control (eg, inhaled

glucocorticoids) Agents for quick relief of ongoing attack (eg,

inhaled SABAs)



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



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


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.


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%

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Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. Chapter 76 Drugs for Asthma.

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