Asthma: Causes, Symptoms, and Categories

Asthma

• Persistent and present most of the time despite treatment
• Recurrent and reversible shortness of breath
• Occurs when the airways of the lungs become narrow due to:
  • Bronchospasms
  • Inflammation of the bronchial mucosa
  • Edema of the bronchial mucosa
  • Production of viscous mucus
• Symptoms:
  • Wheezing
  • Difficulty breathing
  • Coughing at night
• Four categories:
  • Intrinsic (occurring in patients with no history of allergies)
  • Extrinsic (occurring in patients exposed to a known allergen)
  • Exercise-induced
  • Drug-induced (beta blockers, NSAIDS, aspirin, and Motrin)
• Status asthmaticus: prolonged asthma attack that does not respond to typical drug therapy, may last several minutes to hours, and is a medical emergency

Chronic Obstructive Pulmonary Disease (COPD)

• Chronic obstruction of lung airflow that interferes with normal breathing
• Not fully reversible
• Chronic bronchitis and emphysema
• Key areas to watch for:
  • Long-term prevention of hospitalization
  • Decreasing inflammation
  • Opening airways

Emphysema

• Air spaces enlarge as a result of the destruction of alveolar walls
• Caused by the effect of proteolytic enzymes released from leukocytes in response to alveolar inflammation
• The surface area where gas exchange takes place is reduced, impairing effective respiration

Chronic Bronchitis

• Continuous inflammation and low-grade infection of the bronchi
• Excessive secretion of mucus and certain pathologic changes in the bronchial structure
• Often occurs as a result of prolonged exposure to bronchial irritants (smoking, cleaning supplies, pollutants, perfumes)

Bronchodilators

• Relax bronchial smooth muscle, causing dilation of the bronchi and bronchioles that are narrowed as a result of the disease process
• Three classes: beta-adrenergic agonists, anticholinergics, and xanthine derivatives

Beta-Adrenergic Agonists

• Short-acting beta agonist (SABA) inhalers:
  • Albuterol (Ventolin, ProAir)
  • Levalbuterol (Xopenex)
  • Terbutaline (Brethine)
  • Metaproterenol (Alupent)
• Long-acting beta agonist (LABA) inhalers:
  • Arformoterol (Brovana)
  • Formoterol (Foradil, Perforomist)
  • Salmeterol (Serevent)
• Used during acute phase of asthmatic attacks
• Quickly reduce airway constriction and restore normal airflow
• Agonists, or stimulators, of the adrenergic receptors in the sympathetic nervous system

Mechanism of Action and Uses

• Begins at the specific receptor stimulated
• Ends with dilation of the airways
• Activation of beta2 receptors activates cyclic adenosine monophosphate (cAMP), which relaxes smooth muscle in the airway and results in bronchial dilation and increased airflow
• Three types:
  • Nonselective adrenergics (e.g., epinephrine)
  • Nonselective beta-adrenergics (e.g., metaproterenol)
  • Selective beta2 drugs (e.g., albuterol)

Indications and Contraindications

• Albuterol, levavalbuterol:
  • Inhaled short-acting prevention of asthma episode
  • Exercise-induced
  • Inhaled short-acting treatment of bronchospasm and asthma
  • Oral long-acting long-term control of asthma
• Formoterol, salmeterol:
  • Long-term control of asthma
• Terbutaline:
  • Long-term control of asthma
• Contraindications:
  • Tachycardia
  • Angina
  • Nursing actions: dosage might need to be reduced

Adverse Effects

• Insomnia
• Restlessness
• Anorexia
• Vascular headache
• Hyperglycemia
• Tremor
• Cardiac stimulation
• Alpha and beta effects (e.g., epinephrine)
  • Cardiac stimulation
  • Tremor
  • Anginal pain
  • Vascular headache
• Beta1 and beta2 effects (e.g., metaproterenol)
  • Cardiac stimulation
  • Tremor
  • Anginal pain
  • Vascular headache
• Beta2 effects (e.g., albuterol)
  • Hypotension or hypertension
  • Vascular headache
  • Tremor

Interactions

• Use of better adrenergic blockers can negate effects of both medications
• MAOIs and tricyclic antidepressants can increase the risk of tachycardia and angina
• Sympathomimetics:
  • Monitor patients with diabetes; an increase in blood glucose levels can occur

Anticholinergics

• Select prototype medication: ipratropium
• Inhaled short-acting: tiotropium
• Inhaled long-acting: aclidinium
• Pharmacological action:
  • Block muscarinic receptors of the bronchi, resulting in bronchodilation
• Mechanism of action:
  • Acetylcholine (ACh) causes bronchial constriction and narrowing of the airways
  • Anticholinergics bind to the ACh receptors, preventing ACh from binding
  • Result: bronchoconstriction is prevented, airways dilate
• Indications:
  • Prevention of the bronchospasm associated with chronic bronchitis or emphysema
  • Not for the management of acute symptoms
• Adverse effects:
  • Dry mouth or throat
  • Nasal congestion
  • Heart palpitations
  • Gastrointestinal (GI) distress
  • Headache
  • Coughing
  • Anxiety

Xanthine Derivatives

• Plant alkaloids: caffeine, theobromine, and theophylline
• Synthetic xanthine: aminophylline and dyphylline
• Expected pharmacological action:
  • Relaxation of bronchial smooth muscle, resulting in bronchodilation
• Therapeutic uses:
  • Oral theophylline is used for long-term control of chronic asthma or COPD
• Mechanism of action:
  • Increase levels of energy-producing cAMP
  • This is done by competitively inhibiting phosphodiesterase, the enzyme that breaks down cAMP
  • Result: decreased cAMP levels, smooth muscle relaxation, bronchodilation, and increased airflow
  • Cardiovascular stimulation
• Drug effects:
  • Bronchodilation by relaxing smooth muscle in the airways
  • Relief of bronchospasm and greater airflow into and out of the lungs
  • Cardiovascular stimulation: increased force of contraction and increased heart rate, resulting in increased cardiac output and increased blood flow to the kidneys (diuretic effect)
• Indications:
  • Dilation of airways in asthma, chronic bronchitis, and emphysema
  • Mild to moderate cases of acute asthma
  • Not for management of acute asthma attack
  • Adjunct drug in the management of COPD
• Adverse effects:
  • Nausea
  • Vomiting
  • Anorexia
  • Gastroesophageal reflux during sleep
  • Sinus tachycardia
  • Extrasystole
  • Palpitations
  • Ventricular dysrhythmias
  • Transient increased urination
  • Hyperglycemia

Leukotriene Receptor Antagonists (LTRAs)

• Nonbronchodilating
• Newer class of asthma medications
• Currently available drugs:
  • Montelukast
  • Zafirlukast
  • Zileuton
• Mechanism of action:
  • Prevent leukotrienes from attaching to receptors on cells in the lungs and in circulation
  • Inflammation in the lungs is blocked, and asthma symptoms are relieved
• Drug effects:
  • By blocking leukotrienes:
    • Prevent smooth muscle contraction of the bronchial airways
    • Decrease mucus secretion
    • Prevent vascular permeability
    • Decrease neutrophil and leukocyte infiltration to the lungs, preventing inflammation
• Indications:
  • Long-term therapy of asthma in adults and children
  • Prevention of exercise-induced bronchospasm
  • Not meant for management of acute asthma attacks
• Contraindications:
  • Known drug allergy
  • Previous adverse drug reaction
  • Allergy to povidone, lactose, titanium dioxide, or cellulose derivatives is also important to note because these are inactive ingredients in these drugs
  • Use cautiously with clients who have liver dysfunction
• Adverse effects:
  • Headache
  • Nausea
  • Dizziness
  • Insomnia