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U of A NURS 3313 - Antihistamines, Decongestants, Antitussives, and Expectorants Hanna

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Antihistamines, Decongestants, Antitussives, and ExpectorantsUnderstanding the Common Cold- Most caused by viral infection (rhinovirus or influenza virus)- There are 40,000 viruses that cause the common cold - Virus invades tissues (mucosa) of upper respiratory tract, causing upper respiratory infection (URI)- Swollen nasal membranes, swollen lymph glands, etc…- 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 – post nasal drainage, upset stomach- 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 congestionTreatment 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- 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 identifiedAntihistamines- Drugs that directly compete with histamine for specific receptor sites- Two histamine receptorso H1 (histamine1) – allergy and coldso H2 (histamine2) – GI tracts - H1 antagonists are commonly referred to as antihistamines o Examples: chlorpheniramine, fexofenadine (Allegra), loratadine (Claritin), cetirizine (Zyrtec), diphenhydramine (Benadryl) - Antihistamines have several propertieso Antihistaminico Anticholinergic – very drying!o Sedative- Takes at least 4 weeks to appear, take before they get bad- H2 blockers or H2 antagonistso Used to reduce gastric acid in peptic ulcer diseaseo Examples: cimetidine (Tagamet), ranitidine (Zantac), famotidine (Pepcid), nizatidine (Axid)- Mechanism of Actiono Block action of histamine at H1 receptor siteso Compete with histamine for binding at unoccupied receptorso Cannot push histamine off the receptor if already boundo The binding of H1 blockers to the histamine receptors prevents the adverse consequences of histamine stimulation Vasodilation Increased GI and respiratory secretions Increased capillary permeabilityo More effective in preventing the actions of histamine rather than reversing themo Should be given early in treatment, before all the histamine binds to the receptors- Other Effectso Skin – Reduce capillary permeability, wheal-and-flare formation, itchingo Anticholinergic – Drying effect that reduces nasal, salivary, and lacrimal gland secretions (runny nose, tearing, and itching eyes)o Sedative – Some antihistamines cause drowsiness- Indicationso Management of: Nasal allergies Seasonal or perennial allergic rhinitis (hay fever) Allergic reactions Motion sickness Parkinson’s disease – because they are drying  Sleep disorderso Also used to relieve symptoms associated with the common cold Sneezing, runny nose Palliative treatment, not curative- Adverse Effectso Anticholinergic (drying) effects, most common Dry mouth, Difficulty urinating – in really high dose because of the drying, Constipation, or Changes in visiono Drowsiness – Mild drowsiness to deep sleep- Traditional – make you sleepy o Oldero Work both peripherally and centrallyo Have anticholinergic effects, making them more effective than nonsedating drugs in some cases Examples: diphenhydramine (benadryl), brompheniramine, chlorpheniramine, dimenhydrinate, meclizine, promethazine (Phenergan)- All are drying! Don’t give to patients with COPD or emphysema - Nonsedating/Peripherally Acting Antihistamineso Developed to eliminate unwanted adverse effects, mainly sedationo Work peripherally to block the actions of histamine; thus, fewer CNS adverse effectso Longer duration of action (increases compliance) Examples: fexofenadine (Allegra), loratadine (Claritin), cetirizine (Zyrtec)- All used to be prescription - Nursing Implicationso Gather data about the condition or allergic reaction that required treatment; also assess for drug allergieso Contraindicated in the presence of acute asthma attacks and lower respiratory diseases, such as pneumoniao Use with caution in increased intraocular pressure (don’t give to glaucoma patients), cardiac orrenal disease, hypertension, asthma, COPD, peptic ulcer disease, BPH, or pregnancyo Instruct patients to report excessive sedation, confusion, or hypotensiono Instruct patients to avoid driving or operating heavy machinery; advise against consuming alcohol or other CNS depressantso Instruct patients not to take these medications with other prescribed or over-the-counter medications without checking with prescribero Best tolerated when taken with meals—reduces GI upseto If dry mouth occurs, teach patient to perform frequent mouth care, chew gum, or suck on hard candy (preferably sugarless) to ease discomforto Monitor for intended therapeutic effectsHistamine vs. Antihistamine EffectsCardiovascular (small blood vessels)- Histamine effectso Dilation and increased permeability (allowing substances to leak into tissues)- Antihistamine effectso Reduce dilation of blood vessels o Reduce increased permeability of blood vesselsSmooth muscle (on exocrine glands)- Histamine effectso Stimulate salivary, gastric, lacrimal, and bronchial secretions- Antihistamine effectso Reduce salivary, gastric, lacrimal, and bronchial secretionsImmune system (release of substances commonly associated with allergic reactions)- Histamine effectso Mast cells release histamine and other substances, resulting in allergic reactions- Antihistamine effectso Binds to histamine receptors, thus preventing histamine from causing a responseNasal Congestion- Excessive nasal secretions- Inflamed and swollen nasal mucosa- Primary causeso Allergieso Upper respiratory infections (common cold)Decongestants: Types- Three main types are usedo Adrenergics Largest group Sympathomimeticso Anticholinergics – Less commonly usedo Parasympatholytics Corticosteroids Topical, intranasal steroids- Two dosage formso Oral and Inhaled/topically applied to the nasal membranesOral Decongestants- Prolonged decongestant effects, but delayed onset- Effect less potent than topical - No rebound congestion – occurs with nasal


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U of A NURS 3313 - Antihistamines, Decongestants, Antitussives, and Expectorants Hanna

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