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Drugs Affecting the Respiratory System
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Drugs Affecting the Respiratory System
Antihistamines, Decongestants, Antitussives, and Expectorants
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Understanding the Common Cold
Most caused by viral infection (rhinovirus or influenza virus—the “flu”)
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Understanding the Cold
Virus invades tissues (mucosa) of upper respiratory tract, causing upper respiratory infection (URI). Excessive mucus production results from the inflammatory response to this invasion. Fluid drips down the pharynx into the esophagus and lower respiratory tract, causing cold symptoms: sore throat, coughing, upset stomach.
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Irritation of nasal mucosa often triggers the sneeze reflex.
Mucosal irritation also causes release of several inflammatory and vasoactive substances, dilating small blood vessels in the nasal sinuses and causing nasal congestion.
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Involves combined use of antihistamines, nasal decongestants, antitussives, and expectorants.
Treatment is SYMPTOMATIC only, not curative. Symptomatic treatment does not eliminate the causative pathogen.
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Upper Respiratory Tract
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Treatment of the Common Cold
Difficult to identify whether cause is viral or bacterial. Treatment is “empiric therapy,” treating the most likely cause. Antivirals and antibiotics may be used, but viral or bacterial cause may not be easily identified.
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Antihistamines Drugs that directly compete with histamine for specific receptor sites. Two histamine receptors: H1 histamine H2 histamine
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Antihistamines: Mechanism of Action
The binding of H1 blockers to the histamine receptors prevents the adverse consequences of histamine stimulation: Vasodilation Increased gastrointestinal and respiratory secretions Increased capillary permeability
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Histamine vs. Antihistamine Effects
Smooth Muscle (on exocrine glands) Histamine effects: Stimulate salivary, gastric, lacrimal, and bronchial secretions Antihistamine effects: Prevent salivary, gastric, lacrimal, and bronchial secretions
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Histamine vs. Antihistamine Effects
Immune System (Release of substances commonly associated with allergic reactions) Histamine effects: Mast cells release histamine and other substances, resulting in allergic reactions. Antihistamine effect: Binds to histamine receptors, thus preventing histamine from causing a response.
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Antihistamines: Other Effects
Skin: Block capillary permeability, wheal-and-flare formation, itching Anticholinergic: Drying effect that reduces nasal, salivary, and lacrimal gland secretions (runny nose, tearing, and itching eyes) Sedative: Some antihistamines cause drowsiness
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Antihistamines: Therapeutic Uses
Management of: Nasal allergies Seasonal or perennial allergic rhinitis (hay fever) Allergic reactions Motion sickness Sleep disorders
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Antihistamines: Side effects
Anticholinergic (drying) effects, most common: Dry mouth Difficulty urinating Constipation Changes in vision Drowsiness (Mild drowsiness to deep sleep)
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Decongestants
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Nasal Congestion Excessive nasal secretions
Inflamed and swollen nasal mucosa Primary causes: Allergies Upper respiratory infections (common cold)
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Decongestants Two main types are used: Adrenergics (largest group)
Corticosteroids
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Decongestants Two dosage forms: Oral
Inhaled/topically applied to the nasal membranes
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Topical Nasal Decongestants
Adrenergics: ephedrine (Vicks) naphazoline (Privine) oxymetazoline (Afrin) phenylephrine (Neo Synephrine) Intranasal Steroids: beclomethasone dipropionate (Beconase)
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Nasal Decongestants: Therapeutic Uses
Relief of nasal congestion associated with: Acute or chronic rhinitis Common cold Sinusitis Hay fever Other allergies
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Antitussives
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Cough Physiology Respiratory secretions and foreign objects are naturally removed by the cough reflex Induces coughing and expectoration Initiated by irritation of sensory receptors in the respiratory tract
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Two Basic Types of Cough
Productive Cough Congested, removes excessive secretions Nonproductive Cough Dry cough
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Coughing Most of the time, coughing is beneficial
Removes excessive secretions Removes potentially harmful foreign substances In some situations, coughing can be harmful, such as after hernia repair surgery
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Antitussives Drugs used to stop or reduce coughing
Opioid and nonopioid (narcotic and non-narcotic) Used only for NONPRODUCTIVE coughs!
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Antitussives: Mechanism of Action
Opioid Suppress the cough reflex by direct action on the cough center in the medulla. Examples: codeine ,,,hydrocodone
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Antitussives: Mechanism of Action
Nonopioid Suppress the cough reflex by numbing the stretch receptors in the respiratory tract and preventing the cough reflex from being stimulated. Examples: benzonatate (Tessalon) dextromethorphan (Vicks Formula)
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Antitussives: Therapeutic Uses
Used to stop the cough reflex when the cough is nonproductive and/or harmful
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Antitussives: Side Effects
Dextromethorphan Dizziness, drowsiness, nausea Opioids Sedation, nausea, vomiting, lightheadedness, constipation
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Expectorants
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Expectorants Drugs that aid in the expectoration (removal) of mucus
Reduce the viscosity of secretions Disintegrate and thin secretions
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Expectorants: Mechanisms of Action
Direct stimulation or Reflex stimulation Final result: thinner mucus that is easier to remove
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Expectorants: Mechanism of Action
Direct stimulation: The secretory glands are stimulated directly to increase their production of respiratory tract fluids. Examples: iodine-containing products such as iodinated glycerol and potassium iodide (direct and indirect stimulation)
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Expectorants: Mechanism of Action
Reflex stimulation: Agent causes irritation of the GI tract. Loosening and thinning of respiratory tract secretions occur in response to this irritation. Examples: guaifenesin, syrup of ipecac
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Expectorants: Common Side Effects
guaifenesin Nausea, vomiting Gastric irritation
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Nursing Implications: Expectorants
Expectorants should be used with caution in the elderly, or those with asthma or respiratory insufficiency. Patients taking expectorants should receive more fluids, if permitted, to help loosen and liquefy secretions. Report a fever, cough, or other symptoms lasting longer than a week.
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Bronchodilators
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Bronchodilators: Xanthine Derivatives
Plant alkaloids: caffeine, theobromine, and theophylline Only theophylline is used as a bronchodilator
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Bronchodilators: Xanthine Derivatives Side Effects
Nausea, vomiting, anorexia Gastroesophageal reflux during sleep Sinus tachycardia, palpitations, ventricular dysrhythmias Transient increased urination
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