copyright © 2002, 1998, elsevier science (usa). all rights reserved....

Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Antihistamines,Antihistamines,Decongestants,Decongestants,

Antitussives,Antitussives,andand

ExpectorantsExpectorants

D-D-Drugs Affecting theDrugs Affecting theRespiratory SystemRespiratory System


Understanding the Common ColdUnderstanding the Common Cold

• Most caused by viral infection Most caused by viral infection (rhinovirus or influenza virus—the “flu”)(rhinovirus or influenza virus—the “flu”)



• Virus invades tissues (mucosa) of upper Virus invades tissues (mucosa) of upper respiratory tract, causing upper respiratory respiratory tract, causing upper respiratory infection (URI).infection (URI).

• Excessive mucus production results from the Excessive mucus production results from the inflammatory response to this invasion.inflammatory response to this invasion.

• Fluid drips down the pharynx into the Fluid drips down the pharynx into the esophagus and lower respiratory tract, esophagus and lower respiratory tract, causing cold symptoms: sore throat, causing cold symptoms: sore throat, coughing, upset stomach.coughing, upset stomach.



• Irritation of nasal mucosa often triggers the Irritation of nasal mucosa often triggers the sneeze reflex.sneeze reflex.

• Mucosal irritation also causes release of Mucosal irritation also causes release of several inflammatory and vasoactive several inflammatory and vasoactive substances, dilating small blood vessels in substances, dilating small blood vessels in the nasal sinuses and causing nasal the nasal sinuses and causing nasal congestion.congestion.


Treatment of the Common ColdTreatment of the Common Cold

• Involves combined use of antihistamines, Involves combined use of antihistamines, nasal decongestants, antitussives, and nasal decongestants, antitussives, and expectorants.expectorants.

• Treatment is SYMPTOMATIC only, not Treatment is SYMPTOMATIC only, not curative.curative.

• Symptomatic treatment does not eliminate the Symptomatic treatment does not eliminate the causative pathogen.causative pathogen.


Upper Respiratory TractUpper Respiratory Tract


Treatment of the Common ColdTreatment of the Common Cold

• Difficult to identify whether cause is viral or Difficult to identify whether cause is viral or bacterial.bacterial.

• Treatment is “empiric therapy,” treating the Treatment is “empiric therapy,” treating the most likely cause.most likely cause.

• Antivirals and antibiotics may be used, but Antivirals and antibiotics may be used, but viral or bacterial cause may not be easily viral or bacterial cause may not be easily identified.identified.


AntihistaminesAntihistamines

Drugs that directly compete with histamine Drugs that directly compete with histamine for specific receptor sites.for specific receptor sites.•Two histamine receptors:Two histamine receptors:

– HH11 histamine-1 histamine-1– HH22 histamine-2 histamine-2



HH22 Blockers or H Blockers or H22 Antagonists Antagonists– Used to reduce gastric acid in PUDUsed to reduce gastric acid in PUD– Examples: Examples: cimetidine (Tagamet), cimetidine (Tagamet),

ranitidine (Zantac), or ranitidine (Zantac), or famotidine (Pepcid)famotidine (Pepcid)



HH11 antagonists are commonly referred antagonists are commonly referred to asantihistaminesto asantihistamines

•Antihistamines have several effectsAntihistamines have several effects::– AntihistaminicAntihistaminic– AnticholinergicAnticholinergic– SedativeSedative


Antihistamines: Mechanism of ActionAntihistamines: Mechanism of Action

BLOCK action of histamine at the receptor sitesBLOCK action of histamine at the receptor sites•Compete with histamine for binding at unoccupied Compete with histamine for binding at unoccupied

receptors.receptors.•CANNOT push histamine off the receptor if already CANNOT push histamine off the receptor if already

bound.bound.



• The binding of HThe binding of H11 blockers to the histamine blockers to the histamine receptors prevents the adverse receptors prevents the adverse consequences of histamine stimulation:consequences of histamine stimulation:– VasodilationVasodilation– Increased gastrointestinal and respiratory Increased gastrointestinal and respiratory

secretionssecretions– Increased capillary permeabilityIncreased capillary permeability



• More effective in preventing the actions of More effective in preventing the actions of histamine rather than reversing themhistamine rather than reversing them

• Should be given early in treatment, before Should be given early in treatment, before all the histamine binds to the receptorsall the histamine binds to the receptors


Histamine vs. Antihistamine EffectsHistamine vs. Antihistamine Effects

Cardiovascular (small blood vessels)Cardiovascular (small blood vessels)•Histamine effects:Histamine effects:– Dilation and increased permeability Dilation and increased permeability

(allowing substances to leak into tissues)(allowing substances to leak into tissues)•Antihistamine effects:Antihistamine effects:– Prevent dilation of blood vessels Prevent dilation of blood vessels – Prevent increased permeabilityPrevent increased permeability



Smooth Muscle (on exocrine glands)Smooth Muscle (on exocrine glands)•Histamine effects:Histamine effects:– Stimulate salivary, gastric, lacrimal, and Stimulate salivary, gastric, lacrimal, and

bronchial secretionsbronchial secretions•Antihistamine effects:Antihistamine effects:– Prevent salivary, gastric, lacrimal, and Prevent salivary, gastric, lacrimal, and

bronchial secretionsbronchial secretions



Immune System Immune System (Release of substances commonly (Release of substances commonly associated associated with allergic reactions)with allergic reactions)•Histamine effects:Histamine effects:– Mast cells release histamine and other Mast cells release histamine and other

substances, resulting in allergic reactions.substances, resulting in allergic reactions.•Antihistamine effect:Antihistamine effect:– Binds to histamine receptors, thus preventing Binds to histamine receptors, thus preventing

histamine from causing a response.histamine from causing a response.


Antihistamines: Other EffectsAntihistamines: Other Effects

Skin:Skin:•Block capillary permeability, wheal-and-flare Block capillary permeability, wheal-and-flare formation, itchingformation, itching

Anticholinergic:Anticholinergic:•Drying effect that reduces nasal, salivary, and lacrimal Drying effect that reduces nasal, salivary, and lacrimal gland secretions (runny nose, tearing, and itching gland secretions (runny nose, tearing, and itching eyes)eyes)

Sedative:Sedative:•Some antihistamines cause drowsinessSome antihistamines cause drowsiness


Antihistamines: Therapeutic UsesAntihistamines: Therapeutic Uses

Management of:Management of:• Nasal allergiesNasal allergies

• Seasonal or perennial allergic rhinitis Seasonal or perennial allergic rhinitis (hay fever)(hay fever)

• Allergic reactionsAllergic reactions

• Motion sicknessMotion sickness

• Sleep disordersSleep disorders



10 to 20% of general population is sensitive 10 to 20% of general population is sensitive to various environmental allergies.to various environmental allergies.•Histamine-mediated disorders:Histamine-mediated disorders:– Allergic rhinitis Allergic rhinitis

(hay fever, mold and dust allergies)(hay fever, mold and dust allergies)– AnaphylaxisAnaphylaxis– Angioneurotic edemaAngioneurotic edema– Drug feversDrug fevers– Insect bite reactionsInsect bite reactions– Urticaria (itching)Urticaria (itching)


Antihistamines: Therapeutic UsesAntihistamines: Therapeutic Uses

Also used to relieve symptoms associated Also used to relieve symptoms associated with with the common cold:the common cold:

•Sneezing, runny noseSneezing, runny nose•Palliative treatment, not curativePalliative treatment, not curative


Antihistamines: Side effectsAntihistamines: Side effects

• Anticholinergic (drying) effects, most common:Anticholinergic (drying) effects, most common:– Dry mouthDry mouth– Difficulty urinatingDifficulty urinating– ConstipationConstipation– Changes in visionChanges in vision

• DrowsinessDrowsiness– (Mild drowsiness to deep sleep)(Mild drowsiness to deep sleep)


Antihistamines: Two TypesAntihistamines: Two Types

•Traditional Traditional or or

•Nonsedating/Peripherally ActingNonsedating/Peripherally Acting


Antihistamines:Antihistamines:

TraditionalTraditional•OlderOlder•Work both peripherally and centrallyWork both peripherally and centrally•Have anticholinergic effects, making them more Have anticholinergic effects, making them more

effective than nonsedating agents in some caseseffective than nonsedating agents in some cases

Examples:Examples: diphenhydramine (Benadryl)diphenhydramine (Benadryl)chlorpheniramine (Chlor-Trimeton)chlorpheniramine (Chlor-Trimeton)


Antihistamines:Antihistamines:

Nonsedating/Peripherally ActingNonsedating/Peripherally Acting•Developed to eliminate unwanted side effects, Developed to eliminate unwanted side effects,

mainly sedationmainly sedation•Work peripherally to block the actions of histamine; Work peripherally to block the actions of histamine;

thus, fewer CNS side effectsthus, fewer CNS side effects•Longer duration of action (increases compliance)Longer duration of action (increases compliance)

Examples:Examples: fexofenadine (Allegra)fexofenadine (Allegra)loratadine (Claritin)loratadine (Claritin)


: Antihistamines: Antihistamines

• Gather data about the condition or allergic reaction Gather data about the condition or allergic reaction that required treatment; also, assess for drug that required treatment; also, assess for drug allergies.allergies.

• Contraindicated in the presence of acute asthma Contraindicated in the presence of acute asthma attacks and lower respiratory diseases.attacks and lower respiratory diseases.

• Use with caution in increased intraocular pressure, Use with caution in increased intraocular pressure, cardiac or renal disease, hypertension, asthma, cardiac or renal disease, hypertension, asthma, COPD, peptic ulcer disease, BPH, or pregnancy.COPD, peptic ulcer disease, BPH, or pregnancy.



• Instruct patients to report excessive sedation, Instruct patients to report excessive sedation, confusion, or hypotension.confusion, or hypotension.

• Avoid driving or operating heavy machinery, Avoid driving or operating heavy machinery, and do not consume alcohol or other CNS and do not consume alcohol or other CNS depressants.depressants.

• Do not take these medications with other Do not take these medications with other prescribed or OTC medications without prescribed or OTC medications without checking with prescriber.checking with prescriber.



• Best tolerated when taken with meals—Best tolerated when taken with meals—reduces GI upset.reduces GI upset.

• If dry mouth occurs, teach patient to perform If dry mouth occurs, teach patient to perform frequent mouth care, chew gum, or suck on frequent mouth care, chew gum, or suck on hard candy (preferably sugarless) to ease hard candy (preferably sugarless) to ease discomfort.discomfort.

• Monitor for intended therapeutic effects.Monitor for intended therapeutic effects.


DecongestantsDecongestants


Nasal CongestionNasal Congestion

•Excessive nasal secretionsExcessive nasal secretions• Inflamed and swollen nasal mucosaInflamed and swollen nasal mucosa

•Primary causes:Primary causes:– AllergiesAllergies– Upper respiratory infections (common cold)Upper respiratory infections (common cold)



Two main types are used:Two main types are used:•Adrenergics (largest group)Adrenergics (largest group)•CorticosteroidsCorticosteroids



Two dosage forms:Two dosage forms:•OralOral• Inhaled/topically applied to the nasal membranesInhaled/topically applied to the nasal membranes


Oral DecongestantsOral Decongestants

• Prolonged decongestant effects, Prolonged decongestant effects, but delayed onsetbut delayed onset

• Effect less potent than topical Effect less potent than topical • No rebound congestionNo rebound congestion• Exclusively adrenergicsExclusively adrenergics• Examples:Examples: phenylephrine phenylephrine

pseudoephedrine (Sudafed)pseudoephedrine (Sudafed)


Topical Nasal DecongestantsTopical Nasal Decongestants

• Both adrenergics and steroidsBoth adrenergics and steroids• Prompt onsetPrompt onset• PotentPotent• Sustained use over several days causes Sustained use over several days causes

rebound congestion, making the condition rebound congestion, making the condition worseworse


Topical Nasal DecongestantsTopical Nasal Decongestants

• Adrenergics:Adrenergics:ephedrine (Vicks)ephedrine (Vicks) naphazoline (Privine)naphazoline (Privine)oxymetazoline (Afrin)oxymetazoline (Afrin) phenylephrine phenylephrine

(Neo Synephrine)(Neo Synephrine)

• Intranasal Steroids:Intranasal Steroids:beclomethasone dipropionate beclomethasone dipropionate (Beconase, Vancenase)(Beconase, Vancenase)flunisolide (Nasalide)flunisolide (Nasalide)


Nasal Decongestants: Nasal Decongestants: Mechanism of ActionMechanism of Action

Site of action: blood vessels surrounding Site of action: blood vessels surrounding nasal nasal sinusessinuses•AdrenergicsAdrenergics– Constrict small blood vessels that supply Constrict small blood vessels that supply

URI structuresURI structures– As a result, these tissues shrink and nasal As a result, these tissues shrink and nasal

secretions in the swollen mucous membranes secretions in the swollen mucous membranes are are better able to drainbetter able to drain

– Nasal stuffiness is relievedNasal stuffiness is relieved


Nasal Decongestants: Nasal Decongestants: Mechanism of ActionMechanism of Action

Site of action: blood vessels surrounding Site of action: blood vessels surrounding nasal nasal sinusessinuses•Nasal steroidsNasal steroids– Anti-inflammatory effectAnti-inflammatory effect– Work to turn off the immune system cells Work to turn off the immune system cells

involved in the inflammatory responseinvolved in the inflammatory response– Decreased inflammation results in decreased Decreased inflammation results in decreased

congestioncongestion– Nasal stuffiness is relievedNasal stuffiness is relieved


Nasal Decongestants: Drug EffectsNasal Decongestants: Drug Effects

• Shrink engorged nasal mucous membranesShrink engorged nasal mucous membranes• Relieve nasal stuffinessRelieve nasal stuffiness


Nasal Decongestants: Nasal Decongestants: Therapeutic UsesTherapeutic Uses

Relief of nasal congestion associated with:Relief of nasal congestion associated with:•Acute or chronic rhinitisAcute or chronic rhinitis•Common coldCommon cold•SinusitisSinusitis•Hay feverHay fever•Other allergiesOther allergies

May also be used to reduce swelling of the nasal passage and May also be used to reduce swelling of the nasal passage and facilitate visualization of the nasal/pharyngeal membranes before facilitate visualization of the nasal/pharyngeal membranes before surgery or diagnostic procedures.surgery or diagnostic procedures.


Nasal Decongestants: Side EffectsNasal Decongestants: Side Effects

AdrenergicsAdrenergics SteroidsSteroidsnervousnessnervousness local mucosal dryness local mucosal dryness and and irritationirritation

insomniainsomnia

palpitationspalpitations

tremorstremors

(systemic effects due to adrenergic stimulation of (systemic effects due to adrenergic stimulation of the heart, blood vessels, and CNS)the heart, blood vessels, and CNS)


: : Nasal DecongestantsNasal Decongestants

• Decongestants may cause hypertension, Decongestants may cause hypertension, palpitations, and CNS stimulation—avoid in palpitations, and CNS stimulation—avoid in patients with these conditions.patients with these conditions.

• Assess for drug allergies.Assess for drug allergies.


: Decongestants: Decongestants

• Patients should avoid caffeine and caffeine-Patients should avoid caffeine and caffeine-containing products.containing products.

• Report a fever, cough, or other symptoms Report a fever, cough, or other symptoms lasting longer than a week.lasting longer than a week.



AntitussivesAntitussives


Cough PhysiologyCough Physiology

Respiratory secretions and foreign objects are Respiratory secretions and foreign objects are naturally removed by the naturally removed by the •cough reflexcough reflex– Induces coughing and expectorationInduces coughing and expectoration– Initiated by irritation of sensory receptors in the Initiated by irritation of sensory receptors in the

respiratory tractrespiratory tract


Two Basic Types of Cough Two Basic Types of Cough

• Productive CoughProductive Cough– Congested, removes excessive secretionsCongested, removes excessive secretions

• Nonproductive CoughNonproductive Cough– Dry coughDry cough


CoughingCoughing

Most of the time, coughing is beneficialMost of the time, coughing is beneficial•Removes excessive secretionsRemoves excessive secretions•Removes potentially harmful foreign substancesRemoves potentially harmful foreign substances

In some situations, coughing can be harmful, In some situations, coughing can be harmful, such as after hernia repair surgerysuch as after hernia repair surgery


AntitussivesAntitussives

Drugs used to stop or reduce coughingDrugs used to stop or reduce coughing•Opioid and nonopioid Opioid and nonopioid (narcotic (narcotic and non-narcotic)and non-narcotic)

Used only for NONPRODUCTIVE coughs!Used only for NONPRODUCTIVE coughs!


Antitussives: Mechanism of ActionAntitussives: Mechanism of Action

OpioidOpioid•Suppress the cough reflex by direct action on the Suppress the cough reflex by direct action on the cough center in the medulla.cough center in the medulla.

Examples:Examples: codeine (Robitussin A-C, codeine (Robitussin A-C, Dimetane-Dimetane-DC) DC) hydrocodonehydrocodone


Antitussives: Mechanism of ActionAntitussives: Mechanism of Action

NonopioidNonopioid•Suppress the cough reflex by numbing the stretch Suppress the cough reflex by numbing the stretch receptors in the respiratory tract and preventing the receptors in the respiratory tract and preventing the cough reflex from being stimulated.cough reflex from being stimulated.

Examples:Examples: benzonatate (Tessalon)benzonatate (Tessalon)dextromethorphan (Vicks Formula 44,dextromethorphan (Vicks Formula 44,Robitussin-DM)Robitussin-DM)


Antitussives: Therapeutic UsesAntitussives: Therapeutic Uses

• Used to stop the cough reflex when the cough Used to stop the cough reflex when the cough is nonproductive and/or harmfulis nonproductive and/or harmful


Antitussives: Side EffectsAntitussives: Side Effects

BenzonatateBenzonatate•Dizziness, headache, sedationDizziness, headache, sedation

DextromethorphanDextromethorphan•Dizziness, drowsiness, nauseaDizziness, drowsiness, nausea

OpioidsOpioids•Sedation, nausea, vomiting, lightheadedness, Sedation, nausea, vomiting, lightheadedness, constipationconstipation


: : Antitussive AgentsAntitussive Agents

• Perform respiratory and cough assessment, Perform respiratory and cough assessment, and assess for allergies.and assess for allergies.

• Instruct patients to avoid driving or operating Instruct patients to avoid driving or operating heavy equipment due to possible sedation, heavy equipment due to possible sedation, drowsiness, or dizziness.drowsiness, or dizziness.

• If taking chewable tablets or lozenges, If taking chewable tablets or lozenges, do not drink liquids for 30 to 35 minutes do not drink liquids for 30 to 35 minutes afterward.afterward.


: : Antitussive AgentsAntitussive Agents

• Report any of the following symptoms to the Report any of the following symptoms to the caregiver:caregiver:– Cough that lasts more than a weekCough that lasts more than a week– A persistent headacheA persistent headache– Fever Fever – RashRash

• Antitussive agents are for NONPRODUCTIVE Antitussive agents are for NONPRODUCTIVE coughs.coughs.




• Drugs that aid in the expectoration Drugs that aid in the expectoration (removal) of mucus(removal) of mucus

• Reduce the viscosity of secretionsReduce the viscosity of secretions• Disintegrate and thin secretionsDisintegrate and thin secretions


Expectorants: Mechanisms of ActionExpectorants: Mechanisms of Action

•Direct stimulation Direct stimulation oror•Reflex stimulationReflex stimulation

Final result: thinner mucus that is easier to removeFinal result: thinner mucus that is easier to remove


Expectorants: Mechanism of ActionExpectorants: Mechanism of Action

Direct stimulation:Direct stimulation:•The secretory glands are stimulated directly to The secretory glands are stimulated directly to increase their production of respiratory tract fluids.increase their production of respiratory tract fluids.

Examples: terpin hydrate, iodine-containing Examples: terpin hydrate, iodine-containing products such as iodinated glycerol and products such as iodinated glycerol and

potassium iodide (direct and indirect potassium iodide (direct and indirect stimulation)stimulation)


Expectorants: Mechanism of ActionExpectorants: Mechanism of Action

Reflex stimulation:Reflex stimulation:•Agent causes irritation of the GI tract.Agent causes irritation of the GI tract.•Loosening and thinning of respiratory tract secretions Loosening and thinning of respiratory tract secretions occur in response to this irritation.occur in response to this irritation.

Examples: guaifenesin, syrup of ipecacExamples: guaifenesin, syrup of ipecac


Expectorants: Drug EffectsExpectorants: Drug Effects

• By loosening and thinning sputum and By loosening and thinning sputum and bronchial secretions, the tendency to cough is bronchial secretions, the tendency to cough is indirectly diminished.indirectly diminished.


Expectorants: Therapeutic UsesExpectorants: Therapeutic Uses

Used for the relief of nonproductive coughs Used for the relief of nonproductive coughs associated with:associated with:

Common coldCommon cold PertussisPertussis

BronchitisBronchitis InfluenzaInfluenza

LaryngitisLaryngitis MeaslesMeasles

PharyngitisPharyngitis

Coughs caused by chronic paranasal sinusitisCoughs caused by chronic paranasal sinusitis


Expectorants: Common Side EffectsExpectorants: Common Side Effects

guaifenesinguaifenesin terpin hydrateterpin hydrateNausea, vomitingNausea, vomiting Gastric upsetGastric upset

Gastric irritationGastric irritation (Elixir has high alcohol (Elixir has high alcohol content)content)

copyright © 2002, 1998, elsevier science (usa). all rights reserved....

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