CHAPTER 36
Antihistamines, Decongestants,
Antitussives, and Expectorants
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc.,Fall
an affiliate
Elsevier Inc.
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Understanding the Common
Cold
 Most caused by viral infection
(rhinovirus or influenza virus)
 Virus invades tissues (mucosa) of upper
respiratory tract, causing upper respiratory
infection (URI)
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Treatment of the
Common Cold
 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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Antihistamines
 Drugs that directly compete with histamine
for specific receptor sites
 Two histamine receptors
 H1 (histamine1)
 H2 (histamine2)
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Antihistamines (cont’d)
 H1 antagonists are commonly referred to as
antihistamines
 Examples: diphenhydramine (Benadryl),
loratadine (claritin)

Antihistamines have several properties
 Antihistaminic
 Anticholinergic
 Sedative
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Antihistamines (cont’d)
 H2 blockers or H2 antagonists
 Used to reduce gastric acid in peptic ulcer disease
 Examples: cimetidine (Tagamet), ranitidine
(Zantac), famotidine (Pepcid)
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Antihistamines (cont’d)
 10% to 20% of general population is sensitive
to various environmental allergies
 Histamine-mediated disorders
 Allergic rhinitis (hay fever, mold, and dust





allergies)
Anaphylaxis
Angioedema
Drug fevers
Insect bite reactions
Urticaria (itching)
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Antihistamines:
Mechanism of Action
 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
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Antihistamines:
Mechanism of Action (cont’d)
 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
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Antihistamines:
Mechanism of Action (cont’d)
 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
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Histamine vs. Antihistamine
Effects
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
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Histamine vs. Antihistamine
Effects (cont’d)
Smooth muscle (on exocrine glands)
 Histamine effects
 Stimulate salivary, gastric, lacrimal, and
bronchial secretions
 Antihistamine effects
 Reduce salivary, gastric, lacrimal, and
bronchial secretions
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Antihistamines: Other
Effects
 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
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Antihistamines: Indications
 Management of:
 Nasal allergies
 Seasonal or perennial allergic rhinitis




(hay fever)
Allergic reactions
Motion sickness
Parkinson’s disease
Sleep disorders
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Antihistamines: Indications
(cont’d)
 Also used to relieve symptoms associated
with the common cold
Sneezing, runny nose
 Palliative treatment, not curative

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Antihistamines: Adverse Effects
 Anticholinergic (drying) effects, most
common
 Dry mouth
 Difficulty urinating
 Constipation
 Changes in vision
 Drowsiness
 Mild drowsiness to deep sleep
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Antihistamines: Two Types
 Traditional
 Nonsedating/peripherally acting
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Traditional Antihistamines
 Older
 Work both peripherally and centrally
 Have anticholinergic effects, making them
more effective than nonsedating drugs in
some cases
 Examples: diphenhydramine (Benadryl),
chlorpheniramine (Chlor-Trimeton)
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Nonsedating/Peripherally Acting
Antihistamines
 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)
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Antihistamines:
Nursing Implications
 Use with caution in increased intraocular
pressure, cardiac or renal disease,
hypertension, asthma, COPD, peptic ulcer
disease, BPH, or pregnancy
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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: Types
 Three main types are used
 Adrenergics
 Largest group
 Sympathomimetics
 Anticholinergics
 Less commonly used
 Parasympatholytics
 Corticosteroids
 Topical, intranasal steroids
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Decongestants: Types
(cont’d)
 Two dosage forms
 Oral
 Inhaled/topically applied to the nasal
membranes
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Oral Decongestants
 Prolonged decongestant effects, but
delayed onset
 Effect less potent than topical
 No rebound congestion
 Exclusively adrenergics
 Example: pseudoephedrine (Sudafed)
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Topical Nasal Decongestants
 Topical adrenergics
 Prompt onset
 Potent
 Sustained use over several days causes
rebound congestion, making the condition
worse
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Topical Nasal
Decongestants (cont’d)
 Adrenergics
 phenylephrine (Neo-Synephrine)
 Others
 Intranasal steroids
 beclomethasone dipropionate
 flunisolide (Nasalide)
 fluticasone (Flonase)
 Others
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Nasal Decongestants:
Mechanism of Action
Site of action: blood vessels surrounding nasal
sinuses
 Adrenergics
 Constrict small blood vessels that supply URI
structures
 As a result these tissues shrink, and nasal
secretions in the swollen mucous membranes
are better able to drain
 Nasal stuffiness is relieved
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Nasal Decongestants:
Mechanism of Action (cont’d)
 Nasal steroids
 Antiinflammatory effect
 Work to turn off the immune system cells
involved in the inflammatory response
 Decreased inflammation results in decreased
congestion
 Nasal stuffiness is relieved
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Nasal Decongestants:
Indications
 Relief of nasal congestion associated with
 Acute or chronic rhinitis
 Common cold
 Sinusitis
 Hay fever
 Other allergies
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Nasal Decongestants:
Adverse Effects
Adrenergics
Steroids
Nervousness
Local mucosal dryness
Insomnia
and irritation
Palpitations
Tremors
(Systemic effects caused by adrenergic
stimulation of the heart, blood vessels, and
CNS)
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Nasal Decongestants:
Nursing Implications
 Decongestants may cause hypertension,
palpitations, and CNS stimulation—avoid in
patients with these conditions
 Patients on medication therapy for
hypertension should check with their
physician before taking over-the-counter
decongestants
 Assess for drug allergies
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Nasal Decongestants:
Nursing Implications (cont’d)
 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
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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
 Used only for nonproductive coughs!
 May be used in cases where coughing is
harmful
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Antitussives:
Mechanism of Action
Opioids
 Suppress the cough reflex by direct action on the cough
center in the medulla
 Examples:
 codeine (Robitussin A-C, Dimetane-DC)
 hydrocodone
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Antitussives:
Mechanism of Action (cont’d)
Nonopioids
 Suppress the cough reflex by numbing the
stretch receptors in the respiratory tract and
preventing the cough reflex from being
stimulated
 Examples:
 benzonatate (Tessalon Perles)
 dextromethorphan (Vicks Formula 44,
Robitussin-DM)
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Antitussives: Adverse
Effects
 Benzonatate
 Dizziness, headache, sedation, nausea, and
others
 Dextromethorphan
 Dizziness, drowsiness, nausea
 Opioids
 Sedation, nausea, vomiting, lightheadedness,
constipation
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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
 Reflex stimulation
 Final result: thinner mucus that is easier to
remove
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Expectorants:
Mechanism of Action (cont’d)
 Reflex stimulation
 Drug causes irritation of the GI tract
 Loosening and thinning of respiratory tract
secretions occur in response to this irritation
 Example: guaifenesin
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Expectorants:
Mechanism of Action (cont’d)
Direct stimulation
 The secretory glands are stimulated directly to
increase their production of respiratory tract
fluids
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Expectorants: Drug Effects
 By loosening and thinning sputum and
bronchial secretions, the tendency to cough
is indirectly diminished
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Expectorants: Indications
 Used for the relief of productive coughs
associated with
 Common cold
 Bronchitis
 Laryngitis
 Pharyngitis
 Coughs caused by chronic paranasal sinusitis
 Pertussis
 Influenza
 Measles
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Expectorants:
Common Adverse Effects
 guaifenesin
 Nausea, vomiting, gastric irritation
 iodinated glycerol
 GI irritation, rash, enlarged thyroid gland
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Herbal Products: Echinacea
 Reduces symptoms of the common cold and
recovery time
 Adverse effects
 Dermatitis
 GI disturbance
 Dizziness
 Headache
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Expectorants:
Nursing Implications
 Patients taking expectorants should receive
more fluids, if permitted, to help loosen and
liquefy secretions
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