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Chapter 35 Lecture 11

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Chapter 35 Lecture 11Drugs for Common Upper Respiratory InfectionsRespiratory TractUpper respiratory tract includes: nares, nasal cavity, pharynx, and larynx.Lower respiratory tract includes: trachea, bronchi, bronchioles, alveoli, and alveolar-capillary membraneAir enters the upper resp. tract & travels to the lower tract where gas exchange takes placeRespiratory TractRespiration = the process whereby gas exchange occurs at the alveolar-capillary membrane. 3 phases:1. Ventilation - movement of air from the atmosphere through the upper & lower airways to the alveoli2. Perfusion - blood from the pulmonary circulation is adequate at the alveolar-capillary bed3. Diffusion - molecules move from area of higher concentration to lower concentration of gases - O2 passes into the capillary bed to be circulated & CO2 leaves the capillary bed & diffuses into the alveoli for vent. excretionRespiratory TractPerfusion - influenced by alveolar pressure. For gas exchange, the perfusion of each alveoli must be matched by adequate ventilation. Mucosal edema, secretions, & bronchospasms increase the resistance to airflow & dec. ventilation & diffusion of gasesBronchial Smooth Muscle - In the tracheobronchial tube is smooth muscle whose fibers spiral around the tube  contraction  constriction of airway- Parasympathetic Nervous system  releases acetylcholine  bronchoconstriction- Sympathetic Nervous system  releases epinephrine  stimulates beta-2 receptors in bronchial smooth muscle  bronchodilationDrugs for Upper respiratory InfectionsUpper Respiratory Infections (URI’s) = common cold, acute rhinitis, sinusitis, acute tonsillitis, acute laryngitis- The common cold = most expensive > $500 million spent on OTC preparationsCommon Cold & Acute Rhinitis -- Common cold caused by the rhinovirus & affects primarily the nasopharyngeal tract.- Acute rhinitis (inflammation of mucus membranes of nose) usually accompanies the common cold- Allergic rhinitis - caused by pollen or a foreign substanceDrugs for Upper Respiratory InfectionsIncubation period of a cold = 1 to 4 days before onset of symptoms & first 3 days of the cold- Home remedies = rest, chicken soup, hot toddies, Vitamins- 4 groups of drugs used to manage symptoms =antihistamins (H-1 blocker), decongestants (sympathomimetic amines), antitussives, expectorantsDrugs for Upper Respiratory Infections - AntihistaminesAntihistamines or H-1 blockers - compete w/ histamine for receptor sites  prevents a histamine response.2 types of histamine receptors - H-1 & H-2H-1 stimulation = extravascular smooth muscles (including those lining nasal cavity) are constrictedH-2 stimulation = an inc. in gastric secretions = peptic ulcer diseaseDo not confuse the 2 receptors - antihistamines decrease nasopharyngeal secretions by blocking the H-1 receptorDrugs for Upper Respiratory Infections - antihistaminesHistamines - A compound derived from an amino acid histadine. Released in response to an allergic rxn (antigen-antibody rxn) - such as inhaled pollen- When released it reacts w/ H-1 receptors = arterioles & capillaries dialate = inc. in bld flow to the area = capillaries become more permeable = outward passage of fluids into extracellular spaces= edema (congestion) = release of secretions (runny nose & watery eyes)- Large amts. of released histamine in an allergic rxn = extensive arteriolar dilation = dec. BP, skin flushed & edematous = itching, constriction & spasm of bronchioles = SOB & lg. amts. of pulmonary & gastric secretionsDrugs for Upper Respiratory Infections - AntihistaminesAstemizole (Hismanal), Cetirizine (Zertec), Loratadine (Claritin), Chlorpheniramine (Chlortrimeton), Diphenhydramine (Benadryl)Actions = competitive antagonist at the histamine receptor; some also have anticholinergic propertiesUses = Treat colds; perennial/seasonal allergic rhinitis (sneezing, runny nose); allergic activity (drying & sedation); some are also antiemeticSE = Drowsiness, dizziness, sedation, drying effectsCI = glaucoma, acute asthmaDrugs for Upper Respiratory Infections - DecongestantsNasal congestion results from dilation of nasal bld. vessels d/t infection, inflammation, or allergy.With dilation there’s transudation of fluid into tissue spaces  swelling of the nasal cavityDecongestants (sympathomimetic amines)- stimulate alpha-adrenergic receptor  vasoconstriction of capillaries w/in nasal mucosa  shrinking of the nasal mucus membranes & reduction in fluid secretion (runny nose)Drugs for Upper Respiratory Infections - DecongestantsNaphazoline HCL (Allerest), Pseudoephedrine (Actifed, Sudafed), Oxymetolazone (Afrin), Phenylpropanolamine HCL (Allerest, Dimetapp)Use - Congestion d/t common cold, hayfever, upper resp. allergies, sinusitisSE = Jittery,nervous,restless, Inc BP, inc. bld. sugarCI = Hypertension, cardiac disease, diabetesPreparations = nasal spray, tablets, capsules, or liquidFrequent use, esp. nasal spray, can result in tolerance & rebound nasal congestion - d/t irritation of nasal mucosaDrugs for Upper Respiratory Infections - Intranasal GlucocorticoidsBeclomethasone (Beconase, Vancenase, Vanceril), Budesonide (Rhinocort), Dexamethasone (Decadron)fluticasone (Flonase)- Action - steroids used to dec. inflammation locally in the nose- Use - Perennial/seasonal allergic rhinitis (sneezing, runny nose) - May be used alone or w/ antihistamines- SE - rare, but w/ continuous use dryness of the nasal mucosa may occurDrugs for Upper Respiratory Infections - AntitussivesAction - Acts on the cough control center in the medulla to suppress the cough reflexUse - Cough suppression for non-productive irritating coughs* Codeine - Narcotic analgesic to control a cough d/t the common cold or bronchitis* Dextromethorphan - nonnarcotic antitussive that suppresses the cough center in the medulla, widely used- syrup, liquid, chewable & lozenges- SE = drowsiness, sedationDrugs for Upper Respiratory infections - ExpectorantsAction - Loosens bronchial secretions so they can be eliminated w/ coughing* A nonproductive cough becomes more productive and less frequentUses - Nonproductive coughsGuaifenesin (Robitussin) = Most common* Use alone or in combo w/ other resp. drugsHydration is the best expectorantChapter 36Drugs for Acute and ChronicLower Respiratory DisordersDrugs for Lower Respiratory DisordersLung Compliance - Lung volume based on the unit of pressure in the alveoli* Determines the lung’s ability to stretch (tissue elasticity)* Determined


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