chapter 36 antihistamines, decongestants, antitussives, and expectorants copyright © 2014 by mosby,...
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Chapter 36
Antihistamines, Decongestants, Antitussives, and Expectorants
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Most caused by viral infection (rhinovirus or influenza virus)
Virus invades tissues (mucosa) of upper respiratory tract, causing upper respiratory infection (URI)
Understanding the Common Cold
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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
Understanding the Common Cold (cont’d)
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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
Understanding the Common Cold (cont’d)
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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
Treatment of the Common Cold
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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 a definite viral or bacterial cause may not be easily identified
Treatment of the Common Cold (cont’d)
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Classroom Response Question
The common cold is treated with empiric therapy, which means:
A.the medications cure the cold.
B.the medications only treat the symptoms.
C.herbal medications are useful to eliminate symptoms.
D.it is prevented with careful use of medications.
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Drugs that directly compete with histamine for specific receptor sites
Two histamine receptors H1 (histamine1)
H2 (histamine2)
Antihistamines
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H1 antagonists are commonly referred to as antihistamines Examples: chlorpheniramine, fexofenadine (Allegra),
loratadine (Claritin), cetirizine (Zyrtec),diphenhydramine (Benadryl)
Antihistamines have several properties Antihistaminic Anticholinergic Sedative
Antihistamines (cont’d)
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H2 blockers or H2 antagonists Used to reduce gastric acid in peptic ulcer disease Examples: cimetidine (Tagamet), ranitidine (Zantac),
famotidine (Pepcid), nizatidine (Axid)
Antihistamines (cont’d)
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Block action of histamine at H1 receptor sites Compete with histamine for binding at
unoccupied receptors Cannot push histamine off the receptor if already
bound
Antihistamines: Mechanism of Action
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The binding of H1 blockers to the histamine receptors prevents the adverse consequences of histamine stimulation Vasodilation Increased GI and respiratory secretions Increased capillary permeability
Antihistamines: Mechanism of Action (cont’d)
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More effective in preventing the actions of histamine rather than reversing them
Should be given early in treatment, before all the histamine binds to the receptors
Antihistamines: Mechanism of Action (cont’d)
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Cardiovascular (small blood vessels)Histamine effects
Dilation and increased permeability (allowing substances to leak into tissues)
Antihistamine effects Reduce dilation of blood vessels Reduce increased permeability of blood vessels
Histamine vs. Antihistamine Effects
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Smooth muscle (on exocrine glands)Histamine effects
Stimulate salivary, gastric, lacrimal, and bronchial secretions
Antihistamine effects Reduce salivary, gastric, lacrimal, and
bronchial secretions
Histamine vs. Antihistamine Effects (cont’d)
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Immune system (release of substances commonly associated with allergic reactions) Histamine effects
Mast cells release histamine and other substances, resulting in allergic reactions
Antihistamine effects Binds to histamine receptors, thus preventing
histamine from causing a response
Histamine vs. Antihistamine Effects (cont’d)
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Skin Reduce 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
Antihistamines: Other Effects
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Management of: Nasal allergies Seasonal or perennial allergic rhinitis
(hay fever) Allergic reactions Motion sickness Parkinson’s disease Sleep disorders
Antihistamines: Indications
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Also used to relieve symptoms associated with the common cold Sneezing, runny nose Palliative treatment, not curative
Antihistamines: Indications (cont’d)
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Anticholinergic (drying) effects, most common Dry mouth Difficulty urinating Constipation Changes in vision
Drowsiness Mild drowsiness to deep sleep
Antihistamines: Adverse Effects
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Classroom Response Question
Prior to administering an antihistamine to a patient, it is most important for the nurse to assess the patient for a history of which condition?
A. Chronic urticaria
B. Motion sickness
C. Urinary retention
D. Insomnia
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Traditional Nonsedating
Antihistamines: Two Types
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Developed to eliminate unwanted adverse effects, mainly sedation
Work peripherally to block the actions of histamine; thus, fewer CNS adverse effects
Longer duration of action (increases compliance) Examples: fexofenadine (Allegra),
loratadine (Claritin), cetirizine (Zyrtec)
Nonsedating/Peripherally Acting Antihistamines
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Older Work both peripherally and centrally Have anticholinergic effects, making them more
effective than nonsedating drugs in some cases Examples: diphenhydramine, brompheniramine,
chlorpheniramine, dimenhydrinate, meclizine, promethazine
Traditional Antihistamines
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Gather data about the condition or allergic reaction that required treatment; also assess for drug allergies
Contraindicated in the presence of acute asthma attacks and lower respiratory diseases, such as pneumonia
Use with caution in increased intraocular pressure, cardiac or renal disease, hypertension, asthma, COPD, peptic ulcer disease, BPH, or pregnancy
Antihistamines:Nursing Implications
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Instruct patients to report excessive sedation, confusion, or hypotension
Instruct patients to avoid driving or operating heavy machinery; advise against consuming alcohol or other CNS depressants
Instruct patients not to take these medications with other prescribed or over-the-counter medications without checking with prescriber
Antihistamines:Nursing Implications (cont’d)
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Best tolerated when taken with meals—reduces GI upset
If dry mouth occurs, teach patient to perform frequent mouth care, chew gum, or suck on hard candy (preferably sugarless) to ease discomfort
Monitor for intended therapeutic effects
Antihistamines:Nursing Implications (cont’d)
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Excessive nasal secretions Inflamed and swollen nasal mucosa Primary causes
Allergies Upper respiratory infections (common cold)
Nasal Congestion
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Three main types are used Adrenergics
• Largest group
• Sympathomimetics
Anticholinergics• Less commonly used
• Parasympatholytics
Corticosteroids• Topical, intranasal steroids
Decongestants: Types
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Two dosage forms Oral Inhaled/topically applied to the nasal membranes
Decongestants: Types (cont’d)
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Prolonged decongestant effects, but delayed onset
Effect less potent than topical No rebound congestion Exclusively adrenergics Example: pseudoephedrine (Sudafed)
Oral Decongestants
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Topical adrenergics Prompt onset Potent Sustained use over several days causes rebound
congestion, making the condition worse
Topical Nasal Decongestants
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Adrenergics phenylephrine (Neo-Synephrine)
Intranasal steroids beclomethasone dipropionate (Beconase),
budesonide (Rhinocort), flunisolide (Nasalide), fluticasone (Flonase), triamcinolone (Nasacort), ciclesonide (Omnaris)
Intranasal anticholinergic ipratropium (Atrovent)
Topical Nasal Decongestants (cont’d)
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Site of action: blood vessels surrounding nasal sinuses
Adrenergics Constrict small blood vessels that supply upper
respiratory tract structures As a result these tissues shrink, and nasal secretions
in the swollen mucous membranes are better able to drain
Nasal Decongestants:Mechanism of Action
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Nasal steroids Antiinflammatory effect Work to turn off the immune system cells involved in
the inflammatory response Decreased inflammation results in decreased
congestion
Nasal Decongestants:Mechanism of Action (cont’d)
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Shrink engorged nasal mucous membranes Relieve nasal stuffiness
Nasal Decongestants: Drug Effects
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Relief of nasal congestion associated with Acute or chronic rhinitis Common cold Sinusitis Hay fever Other allergies
Nasal Decongestants: Indications
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May also be used to reduce swelling of the nasal passage and facilitate visualization of the nasal/pharyngeal membranes before surgery or diagnostic procedures
Nasal Decongestants: Indications (cont’d)
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Adrenergics Steroids
Nervousness Local mucosal dryness
Insomnia and irritation
Palpitations
Tremors(Systemic effects caused by adrenergic stimulation
of the heart, blood vessels, and CNS)
Nasal Decongestants: Adverse Effects
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Decongestants may cause hypertension, palpitations, and CNS stimulation—avoid in patients with these conditions
Patients on medication therapy for hypertension should check with their prescriber before taking over-the-counter decongestants
Assess for drug allergies
Nasal Decongestants:Nursing Implications
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Patients should avoid caffeine and caffeine-containing products
Report a fever, cough, or other symptoms lasting longer than a week
Monitor for intended therapeutic effects
Nasal Decongestants:Nursing Implications (cont’d)
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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
Cough Physiology
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Productive cough Congested, removes excessive secretions
Nonproductive cough Dry cough
Two Basic Types of Cough
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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
Coughing
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Drugs used to stop or reduce coughing Opioid and nonopioid Used only for nonproductive coughs! May be used in cases where coughing is harmful
Antitussives
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OpioidsSuppress the cough reflex by direct action on the cough center in the medullaExamples:
codeine (Robitussin A-C, Dimetane-DC) hydrocodone
Antitussives: Mechanism of Action
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NonopioidsSuppress the cough reflex by numbing the stretch receptors in the respiratory tract and preventing the cough reflex from being stimulatedExamples:
benzonatate (Tessalon Perles) dextromethorphan (Vicks Formula 44, Robitussin-DM)
Antitussives: Mechanism of Action (cont’d)
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Used to stop the cough reflex when the cough is nonproductive and/or harmful
Antitussives: Indications
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benzonatate Dizziness, headache, sedation, nausea, and others
dextromethorphan Dizziness, drowsiness, nausea
Opioids Sedation, nausea, vomiting, lightheadedness,
constipation
Antitussives: Adverse Effects
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Perform respiratory and cough assessment, and assess for allergies
Instruct patients to avoid driving or operating heavy equipment because of possible sedation, drowsiness, or dizziness
Antitussives:Nursing Implications
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Report any of the following symptoms to the caregiver: Cough that lasts more than a week A persistent headache Fever Rash
Antitussive drugs are for nonproductive coughs Monitor for intended therapeutic effects
Antitussives:Nursing Implications (cont’d)
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Classroom Response Question
A 94-year-old patient has a severe dry cough. He has coughed so hard that the muscles in his chest are hurting. He is unsteady on his feet and slightly confused. Which drug would be the best choice for this patient’s cough?
A.benzonatate (Tessalon Perles) capsules
B.dextromethorphan (Robitussin-DM) oral solution
C.codeine cough syrup
D.guaifenesin (Mucinex)
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Drugs that aid in the expectoration (removal) of mucus
Reduce the viscosity of secretions Disintegrate and thin secretions
Example: guaifenesin (Mucinex)
Expectorants
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Reflex stimulation Direct stimulation Final result: thinner mucus that is easier to
remove
Expectorants: Mechanisms of Action
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Reflex stimulation Drug causes irritation of the GI tract Loosening and thinning of respiratory tract secretions
occur in response to this irritation
Expectorants: Mechanism of Action (cont’d)
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Direct stimulation The secretory glands are stimulated directly to
increase their production of respiratory tract fluids
Expectorants: Mechanism of Action (cont’d)
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By loosening and thinning sputum and bronchial secretions, the tendency to cough is indirectly diminished
Expectorants: Drug Effects
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Used for the relief of productive coughs associated with: Common cold Bronchitis Laryngitis Pharyngitis Coughs caused by chronic paranasal sinusitis Pertussis Influenza Measles
Expectorants: Indications
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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
Monitor for intended therapeutic effects
Expectorants:Nursing Implications
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Reduces symptoms of the common cold and recovery time
Adverse effects Dermatitis GI disturbance Dizziness Headache
Herbal Products: Echinacea
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Classroom Response Question
A patient with a tracheostomy developed pneumonia. It is very difficult for the patient to cough up the thick, dry secretions he has developed. The nurse identifies which drug as being most effective in helping this patient?
A.benzonatate (Tessalon Perles) capsules
B.dextromethorphan (Robitussin-DM) oral solution
C.codeine cough syrup
D.guaifenesin (Mucinex)
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