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Friday, September 26, 2008

Antihistamines (Clinical Nclex Pharmacology)

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Antihistamines (Clinical Pharmacology) Slideshow Transcript
Slide 1: Drugs Affecting the Respiratory System Antihistamines, Decongestants, Antitussives, and Expectorants Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 2: Understanding the Common Cold • Most caused by viral infection (rhinovirus or influenza virus—the “flu”) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 3: Understanding the Common Cold • Virus invades tissues (mucosa) of upper respiratory tract, causing upper respiratory infection (URI). • 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. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 4: Understanding the Common Cold • 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. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 5: 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. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 6: Instructors may want to use EIC Image #83: Upper Respiratory Tract Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 7: Treatment of the Common Cold • 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 viral or bacterial cause may not be easily identified. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 8: Antihistamines Drugs that directly compete with histamine for specific receptor sites. • Two histamine receptors: – H1 histamine-1 – H2 histamine-2 Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 9: Antihistamines H2 Blockers or H2 Antagonists – Used to reduce gastric acid in PUD – Examples: cimetidine (Tagamet), ranitidine (Zantac), or famotidine (Pepcid) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 10: Antihistamines H1 antagonists are commonly referred to asantihistamines • Antihistamines have several effects: – Antihistaminic – Anticholinergic – Sedative Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 11: Antihistamines: Mechanism of Action BLOCK action of histamine at the receptor sites • Compete with histamine for binding at unoccupied receptors. • CANNOT push histamine off the receptor if already bound. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 12: Antihistamines: Mechanism of Action • The binding of H1 blockers to the histamine receptors prevents the adverse consequences of histamine stimulation: – Vasodilation – Increased gastrointestinal and respiratory secretions – Increased capillary permeability Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 13: Antihistamines: Mechanism of Action • 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 Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 14: Histamine vs. Antihistamine Effects Cardiovascular (small blood vessels) • Histamine effects: – Dilation and increased permeability (allowing substances to leak into tissues) • Antihistamine effects: – Prevent dilation of blood vessels – Prevent increased permeability Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 15: Histamine vs. Antihistamine Effects Smooth Muscle (on exocrine glands) • Histamine effects: – Stimulate salivary, gastric, lacrimal, and bronchial secretions • Antihistamine effects: – Prevent salivary, gastric, lacrimal, and bronchial secretions Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 16: Histamine vs. Antihistamine Effects Immune System (Release of substances commonly associated with allergic reactions) • Histamine effects: – Mast cells release histamine and other substances, resulting in allergic reactions. • Antihistamine effect: – Binds to histamine receptors, thus preventing histamine from causing a response. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 17: Antihistamines: Other Effects Skin: • Block 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 Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 18: Antihistamines: Therapeutic Uses Management of: • Nasal allergies • Seasonal or perennial allergic rhinitis (hay fever) • Allergic reactions • Motion sickness • Sleep disorders Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 19: Antihistamines 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) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 20: Antihistamines: Therapeutic Uses Also used to relieve symptoms associated with the common cold: • Sneezing, runny nose • Palliative treatment, not curative Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 21: Antihistamines: Side effects • Anticholinergic (drying) effects, most common: – Dry mouth – Difficulty urinating – Constipation – Changes in vision • Drowsiness – (Mild drowsiness to deep sleep) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 22: Antihistamines: Two Types • Traditional or • Nonsedating/Peripherally Acting Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 23: Antihistamines: Traditional • Older • Work both peripherally and centrally • Have anticholinergic effects, making them more effective than nonsedating agents in some cases Examples: diphenhydramine (Benadryl) chlorpheniramine (Chlor-Trimeton) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 24: Antihistamines: Nonsedating/Peripherally Acting • Developed to eliminate unwanted side effects, mainly sedation • Work peripherally to block the actions of histamine; thus, fewer CNS side effects • Longer duration of action (increases compliance) Examples: fexofenadine (Allegra) loratadine (Claritin) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 25: Nursing Implications: Antihistamines • 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. • Use with caution in increased intraocular pressure, cardiac or renal disease, hypertension, asthma, COPD, peptic ulcer disease, BPH, or pregnancy. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 26: Nursing Implications: Antihistamines • Instruct patients to report excessive sedation, confusion, or hypotension. • Avoid driving or operating heavy machinery, and do not consume alcohol or other CNS depressants. • Do not take these medications with other prescribed or OTC medications without checking with prescriber. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 27: Nursing Implications: Antihistamines • 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. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 28: Decongestants Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 29: Nasal Congestion • Excessive nasal secretions • Inflamed and swollen nasal mucosa • Primary causes: – Allergies – Upper respiratory infections (common cold) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 30: Decongestants Two main types are used: • Adrenergics (largest group) • Corticosteroids Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 31: Decongestants Two dosage forms: • Oral • Inhaled/topically applied to the nasal membranes Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 32: Oral Decongestants • Prolonged decongestant effects, but delayed onset • Effect less potent than topical • No rebound congestion • Exclusively adrenergics • Examples: phenylephrine pseudoephedrine (Sudafed) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 33: Topical Nasal Decongestants • Both adrenergics and steroids • Prompt onset • Potent • Sustained use over several days causes rebound congestion, making the condition worse Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 34: Topical Nasal Decongestants • Adrenergics: ephedrine (Vicks) naphazoline (Privine) oxymetazoline (Afrin) phenylephrine (Neo Synephrine) • Intranasal Steroids: beclomethasone dipropionate (Beconase, Vancenase) flunisolide (Nasalide) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 35: 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 Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 36: Nasal Decongestants: Mechanism of Action Site of action: blood vessels surrounding nasal sinuses • Nasal steroids – Anti-inflammatory effect – Work to turn off the immune system cells involved in the inflammatory response – Decreased inflammation results in decreased congestion – Nasal stuffiness is relieved Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 37: Nasal Decongestants: Drug Effects • Shrink engorged nasal mucous membranes • Relieve nasal stuffiness Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 38: Nasal Decongestants: Therapeutic Uses Relief of nasal congestion associated with: • Acute or chronic rhinitis • Common cold • Sinusitis • Hay fever • Other allergies May also be used to reduce swelling of the nasal passage and facilitate visualization of the nasal/pharyngeal membranes before surgery or diagnostic procedures. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 39: Nasal Decongestants: Side Effects Adrenergics Steroids nervousness local mucosal dryness and irritation insomnia palpitations tremors (systemic effects due to adrenergic stimulation of the heart, blood vessels, and CNS) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 40: Nursing Implications: Nasal Decongestants • Decongestants may cause hypertension, palpitations, and CNS stimulation—avoid in patients with these conditions. • Assess for drug allergies. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 41: Nursing Implications: Decongestants • 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. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 42: Antitussives Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 43: 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 Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 44: Two Basic Types of Cough • Productive Cough – Congested, removes excessive secretions • Nonproductive Cough – Dry cough Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 45: 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 Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 46: Antitussives Drugs used to stop or reduce coughing • Opioid and nonopioid (narcotic and non-narcotic) Used only for NONPRODUCTIVE coughs! Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 47: Antitussives: Mechanism of Action Opioid • Suppress the cough reflex by direct action on the cough center in the medulla. Examples: codeine (Robitussin A-C, Dimetane-DC) hydrocodone Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 48: Antitussives: Mechanism of Action Nonopioid • Suppress the cough reflex by numbing the stretch receptors in the respiratory tract and preventing the cough reflex from being stimulated. Examples: benzonatate (Tessalon) dextromethorphan (Vicks Formula 44, Robitussin-DM) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 49: Antitussives: Therapeutic Uses • Used to stop the cough reflex when the cough is nonproductive and/or harmful Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 50: Antitussives: Side Effects Benzonatate • Dizziness, headache, sedation Dextromethorphan • Dizziness, drowsiness, nausea Opioids • Sedation, nausea, vomiting, lightheadedness, constipation Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 51: Nursing Implications: Antitussive Agents • Perform respiratory and cough assessment, and assess for allergies. • Instruct patients to avoid driving or operating heavy equipment due to possible sedation, drowsiness, or dizziness. • If taking chewable tablets or lozenges, do not drink liquids for 30 to 35 minutes afterward. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 52: Nursing Implications: Antitussive Agents • Report any of the following symptoms to the caregiver: – Cough that lasts more than a week – A persistent headache – Fever – Rash • Antitussive agents are for NONPRODUCTIVE coughs. • Monitor for intended therapeutic effects. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 53: Expectorants Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 54: Expectorants • Drugs that aid in the expectoration (removal) of mucus • Reduce the viscosity of secretions • Disintegrate and thin secretions Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 55: Expectorants: Mechanisms of Action • Direct stimulation or • Reflex stimulation Final result: thinner mucus that is easier to remove Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 56: Expectorants: Mechanism of Action Direct stimulation: • The secretory glands are stimulated directly to increase their production of respiratory tract fluids. Examples: terpin hydrate, iodine-containing products such as iodinated glycerol and potassium iodide (direct and indirect stimulation) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 57: Expectorants: Mechanism of Action Reflex stimulation: • Agent causes irritation of the GI tract. • Loosening and thinning of respiratory tract secretions occur in response to this irritation. Examples: guaifenesin, syrup of ipecac Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 58: Expectorants: Drug Effects • By loosening and thinning sputum and bronchial secretions, the tendency to cough is indirectly diminished. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 59: Expectorants: Therapeutic Uses Used for the relief of nonproductive coughs associated with: Common cold Pertussis Bronchitis Influenza Laryngitis Measles Pharyngitis Coughs caused by chronic paranasal sinusitis Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 60: Expectorants: Common Side Effects guaifenesin terpin hydrate Nausea, vomiting Gastric upset Gastric irritation (Elixir has high alcohol content) Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.

Slide 61: Nursing Implications: Expectorants • 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. Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.




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