CHAPTER 36
Antihistamines, Decongestants,
Antitussives, and Expectorants
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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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Understanding the
Common Cold (cont’d)


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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Understanding the
Common Cold (cont’d)


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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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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Treatment of the
Common Cold (cont’d)



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
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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
Angioneurotic edema
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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Histamine vs. Antihistamine
Effects (cont’d)
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
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Antihistamines: Other Effects

Skin


Anticholinergic


Reduce capillary permeability, wheal-and-flare formation,
itching
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



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
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Antihistamines:
Nursing Implications (cont’d)



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 overthe-counter medications without checking
with prescriber
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Antihistamines:
Nursing Implications (cont’d)



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
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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:
Drug Effects


Shrink engorged nasal mucous membranes
Relieve nasal stuffiness
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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:
Indications (cont’d)

May also be used to reduce swelling of the
nasal passage and facilitate visualization of
the nasal/pharyngeal membranes before
surgery or diagnostic procedures
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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: Indications

Used to stop the cough reflex when the
cough is nonproductive and/or harmful
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Antitussives: Adverse Effects

Benzonatate


Dextromethorphan


Dizziness, headache, sedation, nausea, and
others
Dizziness, drowsiness, nausea
Opioids

Sedation, nausea, vomiting, lightheadedness,
constipation
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Antitussives:
Nursing Implications



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
Patients taking chewable tablets or lozenges
should not drink liquids for 30 to 35 minutes
afterward
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Antitussives:
Nursing Implications (cont’d)

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
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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




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
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