Asthma Flashcards
Pathophysiology
Symptoms of asthma result from a combination of inflammation and bronchoconstriction, so treatment must address both components
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
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
Glucocorticoids
Include budesonide and fluticasone, usually administered by inhalation, but IV and oral are also options; mechanism of action: suppress inflammation; adverse effects: minor when taken acutely, can be severe when used long-term (adrenal suppression, osteoporosis, hyperglycemia)
Leukotriene Modifiers
Suppress effects of leukotrienes, less effective than inhaled glucocorticoids; available agents: zileuton (Zyflo), zarfirlukast (Accolate), montelukast (Singulair)
Cromolyn
Used for prophylaxis, not for quick relief; supresses 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 be taking a glucocorticoid for long-term suppression of inflammation
-Principal bronchodilators are the beta2-adrengergic agonists
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
Beta2-Adrenergic Agonists: adverse effects
Inhaled preparations
-systemic effects: tachycardia, angina, and tremor
Oral preparations
-excessive dosage: angina pectoris, tachydysrhythmias; tremor
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
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: aminophylline, dyphylline
Glucocorticoid/LABA Combinations
Available combinations: fluticason/salmeterol (Advair), budesonide/formoterol (Symbicort); indicated for long term maintenance in adults and children, not recommended for initial therapy
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 of chronic asthma
Reducing impairment, reducing risk
Long term drug therapy of Chronic Asthma
Agents for long term control (eg. inhaled glucocorticoids), agents for quick relief of ongoing attacks (eg. inhaled SABAs)
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
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:
1. Oxygen to relieve hypoxemia
2. Systemic glucocorticoid to reduce airway inflammation
3. Nebulized high-dose SABA to relieve airway obstruction
4. 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 pt’s pillows, mattress, box spring with covers impermeable to allergens, washing all bedding weekly in a hot water cycle, removing carpeting or rugs, keeping indoor humidity below 50%
