Antihistamines Decongestants Antitussives and Expectorants Understanding 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 congestion 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 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 identified Antihistamines Drugs that directly compete with histamine for specific receptor sites Two histamine receptors o H1 histamine1 allergy and colds o 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 properties o Antihistaminic o Anticholinergic very drying o Sedative Takes at least 4 weeks to appear take before they get bad H2 blockers or H2 antagonists o Used to reduce gastric acid in peptic ulcer disease o Examples cimetidine Tagamet ranitidine Zantac famotidine Pepcid nizatidine Axid Mechanism of Action o Block action of histamine at H1 receptor sites o Compete with histamine for binding at unoccupied receptors o Cannot push histamine off the receptor if already bound o The binding of H1 blockers to the histamine receptors prevents the adverse consequences of histamine stimulation Vasodilation Increased GI and respiratory secretions Increased capillary permeability o More effective in preventing the actions of histamine rather than reversing them o Should be given early in treatment before all the histamine binds to the receptors Other Effects o Skin Reduce capillary permeability wheal and flare formation itching o Anticholinergic Drying effect that reduces nasal salivary and lacrimal gland secretions runny nose tearing and itching eyes o Sedative Some antihistamines cause drowsiness Indications o Management of Nasal allergies Seasonal or perennial allergic rhinitis hay fever Allergic reactions Motion sickness Parkinson s disease because they are drying Sleep disorders o Also used to relieve symptoms associated with the common cold Sneezing runny nose Palliative treatment not curative Adverse Effects o Anticholinergic drying effects most common Dry mouth Difficulty urinating in really high dose because of the drying Constipation or Changes in vision o Drowsiness Mild drowsiness to deep sleep Traditional make you sleepy o Older o Work both peripherally and centrally o 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 Antihistamines o Developed to eliminate unwanted adverse effects mainly sedation o Work peripherally to block the actions of histamine thus fewer CNS adverse effects o Longer duration of action increases compliance Examples fexofenadine Allegra loratadine Claritin cetirizine Zyrtec All used to be prescription Nursing Implications o Gather data about the condition or allergic reaction that required treatment also assess for drug allergies o Contraindicated in the presence of acute asthma attacks and lower respiratory diseases such as pneumonia o Use with caution in increased intraocular pressure don t give to glaucoma patients cardiac or renal disease hypertension asthma COPD peptic ulcer disease BPH or pregnancy o Instruct patients to report excessive sedation confusion or hypotension o Instruct patients to avoid driving or operating heavy machinery advise against consuming alcohol or other CNS depressants o Instruct patients not to take these medications with other prescribed or over the counter medications without checking with prescriber o Best tolerated when taken with meals reduces GI upset o If dry mouth occurs teach patient to perform frequent mouth care chew gum or suck on hard candy preferably sugarless to ease discomfort o Monitor for intended therapeutic effects Histamine vs Antihistamine Effects Cardiovascular small blood vessels Histamine effects o Dilation and increased permeability allowing substances to leak into tissues Antihistamine effects o Reduce dilation of blood vessels o Reduce increased permeability of blood vessels Smooth muscle on exocrine glands Histamine effects o Stimulate salivary gastric lacrimal and bronchial secretions Antihistamine effects o Reduce salivary gastric lacrimal and bronchial secretions Immune system release of substances commonly associated with allergic reactions Histamine effects o Mast cells release histamine and other substances resulting in allergic reactions Antihistamine effects o Binds to histamine receptors thus preventing histamine from causing a response Nasal Congestion Excessive nasal secretions Inflamed and swollen nasal mucosa Primary causes o Allergies o Upper respiratory infections common cold Decongestants Types Three main types are used o Adrenergics Largest group Sympathomimetics o Anticholinergics Less commonly used o Parasympatholytics Corticosteroids Topical intranasal steroids Two dosage forms o Oral and Inhaled topically applied to the nasal membranes Oral Decongestants Prolonged decongestant effects but delayed onset Effect less potent than topical No rebound congestion occurs with nasal sprays Exclusively adrenergics Example pseudoephedrine Sudafed the best on the market Topical Nasal Decongestants Topical adrenergics o Prompt onset o Potent o Sustained use over several days causes rebound congestion making the condition worse Adrenergics