Respiratory Pharmacology

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Prajogo Wibowo

Antihistamines, Decongestants, Antitussives, and Expectorants

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AntihistaminesDrugs that directly compete with histamine for specific receptor sitesTwo histamine receptorsH1 (histamine1)H2 (histamine2)

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Antihistamines (cont'd)H2 blockers or H2 antagonistsUsed to reduce gastric acid in PUDExamples: cimetidine (Tagamet), ranitidine (Zantac), famotidine (Pepcid)

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Antihistamines (cont'd)H1 antagonists are commonly referred to as antihistaminesAntihistamines have several propertiesAntihistaminicAnticholinergicSedative

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Antihistamines (cont'd)10% to 20% of general population is sensitive to various environmental allergiesHistamine-mediated disordersAllergic rhinitis (hay fever, mold and dust allergies)AnaphylaxisAngioneurotic edemaDrug feversInsect bite reactionsUrticaria (itching)

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Antihistamines: Mechanism of ActionBlock action of histamine at the H1 receptor sitesCompete with histamine for binding at unoccupied receptorsCannot push histamine off the receptor if already bound

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Antihistamines: Mechanism of Action (cont'd)Prevents the adverse consequences of histamine stimulationVasodilationIncreased GI and respiratory secretionsIncreased capillary permeability

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Antihistamines: Mechanism of Action (cont'd)More effective in preventing the actions of histamine rather than reversing themShould be given early in treatment, before all the histamine binds to the receptors

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Antihistamines: EffectsSkin & C-VReduce capillary permeability, wheal-and-flare formation, itching, flushing d/t vasodilationAnticholinergicDrying effect that reduces nasal, salivary, and lacrimal gland secretions (runny nose, tearing, and itching eyes)SedativeSome antihistamines cause drowsiness

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Antihistamines: IndicationsManagement of:Nasal allergiesSeasonal or perennial allergic rhinitis (hay fever)Allergic reactionsMotion sicknessSleep disorders

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Antihistamines: Indications (cont'd)Also used to relieve symptoms associated with the common coldSneezing, runny nosePalliative treatment, not curative

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Antihistamines: Side effectsAnticholinergic (drying) effects, most commonDry mouthDifficulty urinatingConstipationChanges in visionDrowsinessMild drowsiness to deep sleep

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Antihistamines: Two TypesTraditionalNonsedating/peripherally acting

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Traditional AntihistaminesOlderWork both peripherally and centrallyHave anticholinergic effects, making them more effective than nonsedating agents in some casesExamples: diphenhydramine (Benadryl); chlorpheniramine (Chlor-Trimeton)

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Nonsedating/Peripherally Acting AntihistaminesDeveloped to eliminate unwanted side effects, mainly sedationWork peripherally to block the actions of histamine; thus, fewer CNS side effectsLonger duration of action (increases compliance)Examples: fexofenadine (Allegra), loratadine (Claritin), cetirizine (Zyrtec)

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Antihistamines:Nursing ImplicationsGather data about the condition or allergic reaction that required treatment; also assess for drug allergiesContraindicated in the presence of acute asthma attacks and lower respiratory diseasesUse 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 ImplicationsInstruct patients to report excessive sedation, confusion, or hypotensionAvoid driving or operating heavy machinery, and do not consume alcohol or other CNS depressantsDo not take these medications with other prescribed or OTC medications without checking with prescriber

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Antihistamines:Nursing ImplicationsBest tolerated when taken with mealsreduces GI upsetIf dry mouth occurs, teach patient to perform frequent mouth care, chew gum, or suck on hard candy (preferably sugarless) to ease discomfortMonitor for intended therapeutic effects

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Decongestants

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Nasal CongestionExcessive nasal secretionsInflamed and swollen nasal mucosaPrimary causesAllergiesUpper respiratory infections (common cold)

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Decongestants: TypesThree main types are usedAdrenergicsLargest groupSympathomimeticsAnticholinergicsLess commonly usedParasympatholyticsCorticosteroidsTopical

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Decongestants: Types (cont'd)Two dosage formsOralInhaled/topically applied to the nasal membranes

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Oral DecongestantsProlonged decongestant effects, but delayed onsetEffect less potent than topical No rebound congestionExclusively adrenergicsExample: pseudoephedrine (Sudafed)

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Topical Nasal DecongestantsTopical adrenergicsPrompt onsetPotentSustained use over several days causes rebound congestion, making the condition worse

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Topical Nasal Decongestants (cont'd)Adrenergicsdesoxyephedrine (Vicks)phenylephrine (Neo-Synephrine)Intranasal steroidsbeclomethasone dipropionate (Beconase, Vancenase)flunisolide (Nasalide)fluticasone (Flonase)

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Nasal Decongestants: Drug EffectsShrink engorged nasal mucous membranesRelieve nasal stuffiness

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Nasal Decongestants: IndicationsRelief of nasal congestion associated with:Acute or chronic rhinitisCommon coldSinusitisHay feverOther 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: Side EffectsAdrenergicsSteroidsNervousnessLocal mucosal drynessInsomnia and irritationPalpitationsTremors(systemic effects due to adrenergic stimulation of the heart, blood vessels, and CNS)

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Nasal Decongestants:Nursing ImplicationsDecongestants may cause hypertension, palpitations, and CNS stimulationavoid in patients with these conditionsPatients on medication therapy for hypertension should check with their physician before taking OTC decongestantsAssess for drug allergies

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Nasal Decongestants:Nursing ImplicationsPatients should avoid caffeine and caffeine-containing productsReport a fever, cough, or other symptoms lasting longer than a weekMonitor for intended therapeutic effects

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Antitussives

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Cough PhysiologyCough reflexInduces coughing and expectorationInitiated by irritation of sensory receptors in the respiratory tract

To remove secretions or foreign objects

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Two Basic Types of Cough Productive coughCongested, removes excessive secretionsNonproductive coughDry cough

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CoughingMost of the time, coughing is beneficialRemoves excessive secretionsRemoves potentially harmful foreign substancesIn some situations, coughing can be harmful, such as after hernia repair surgery

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Antitussives: DefinitionDrugs used to stop or reduce coughingOpioid and nonopioid (narcotic and nonnarcotic)Used only for nonproductive coughs!

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Antitussives: Mechanism of ActionOpioidsSuppress the cough reflex by acting on the cough center in the medullaExamples:codeine (Robitussin A-C, Dimetane-DC)hydrocodone

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Antitussives: Mechanism of Action (cont'd)NonopioidsSuppress the cough reflex by preventing the cough reflex from being stimulatedExamples:benzonatate (Tessalon Perles)dextromethorphan (Vicks Formula 44, Robitussin-DM)

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Antitussives: IndicationsUsed to stop the cough reflex when the cough is nonproductive and/or harmful

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Antitussives: Side EffectsBenzonatateDizziness, headache, sedation, nausea, and othersDextromethorphanDizziness, drowsiness, nauseaOpioidsSedation, nausea, vomiting, lightheadedness, constipation

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Antitussive Agents:Nursing ImplicationsPerform respiratory and cough assessment, and assess for allergiesInstruct patients to avoid driving or operating heavy equipment due to possible sedation, drowsiness, or dizzinessIf taking chewable tablets or lozenges, do not drink liquids for 30 to 35 minutes afterward

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Antitussive Agents:Nursing ImplicationsReport any of the following symptoms to the caregiverCough that lasts more than a weekA persistent headacheFever RashAntitussive agents are for nonproductive coughsMonitor for intended therapeutic effects

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Expectorants

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Expectorants: DefinitionDrugs that aid in the expectoration (removal) of mucusReduce the viscosity of secretionsDisintegrate and thin secretions

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Expectorants: Mechanisms of ActionDirect stimulationReflex stimulation

Final result: thinner mucus that is easier to remove

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Expectorants: Mechanism of Action (cont'd)Reflex stimulationAgent causes irritation of the GI tractLoosening and thinning of respiratory tract secretions occur in response to this irritationExample: guaifenesin

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Expectorants: Mechanism of Action (cont'd)Direct stimulationThe secretory glands are stimulated directly to increase their production of respiratory tract fluidsExamples: iodine-containing products such as iodinated glycerol and potassium iodide

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Expectorants: Drug EffectsBy loosening and thinning sputum and bronchial secretions, the tendency to cough is indirectly diminished

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Expectorants: Common Side EffectsguaifenesinNausea, vomiting, gastric irritationiodinated glycerolGI irritation, rash, enlarged thyroid glandpotassium iodideIodism, nausea, vomiting, taste perversion

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Expectorants:Nursing ImplicationsExpectorants should be used with caution in the elderly or those with asthma or respiratory insufficiencyPatients taking expectorants should receive more fluids, if permitted, to help loosen and liquefy secretionsReport a fever, cough, or other symptoms lasting longer than a weekMonitor for intended therapeutic effects

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