NURS 125 Chapter 36 Student Notes PDF

Chapter 36: Antihistamines, Decongestants, Antitussives, and Expectorants This chapter focuses on common medications used to alleviate symptoms associated with allergies, colds, and other respiratory conditions. We will delve into the mechanisms of action, clinical applications, and potential advers...

Chapter 36: Antihistamines, Decongestants, Antitussives, and Expectorants This chapter focuses on common medications used to alleviate symptoms associated with allergies, colds, and other respiratory conditions. We will delve into the mechanisms of action, clinical applications, and potential adverse effects of these drugs. KR by Katie Robinson Understanding the Common Cold Viral Infection The common cold is most commonly caused by rhinoviruses or influenza viruses. Upper Respiratory Tract These viruses invade the mucous membranes of the upper respiratory tract, causing an upper respiratory infection. Symptoms Common cold symptoms include runny nose, sore throat, cough, and sneezing. Understanding the Common Cold (Cont.) Mucus Production Common Cold Symptoms The common cold is a viral infection. Our As the mucus drips down the pharynx, it can immune system responds by releasing chemicals irritate the throat, leading to a sore throat. It can to fight the virus, leading to inflammation. also cause coughing as the body tries to clear the airways. Excessive mucus production is caused by the Some of the mucus may also drip into the inflammatory response. This mucus is thick and esophagus and lower respiratory tract, sticky, and it is designed to trap the virus and potentially causing a cough, upset stomach, and prevent it from spreading. other symptoms. Common Cold Symptoms (Cont.) Sneezing Nasal Congestion Irritation of the nasal Mucosal irritation mucosa triggers the causes the release of sneeze reflex, expelling inflammatory air and mucus from the substances, dilating nasal passages. blood vessels in the nasal sinuses and leading to congestion. Treatment of the Common Cold Symptomatic Relief Antiviral Therapy Treatment focuses on There are no effective alleviating symptoms, antiviral therapies not eliminating the available for the underlying cause. common cold. Antihistamines Nasal Decongestants Can be used to Help relieve nasal manage sneezing and congestion by runny nose, but their shrinking swollen effectiveness is nasal passages. limited. Empiric Therapy for Common Cold Difficult to Identify Cause Empiric Therapy Antivirals and Antibiotics Viral or bacterial cause of the Treatment focuses on treating May be used, but definite viral common cold can be difficult to the most likely cause, or bacterial cause may not be pinpoint. regardless of confirmation. easy to identify. Antihistamines Receptor Sites Antihistamines directly compete with histamine. Histamine Receptors Two types of histamine receptors, H1 and H2. Mechanism of Action Antihistamines block the action of histamine. Anaphylaxis: Severe Allergic Reactions Histamine Release Smooth Muscle Constriction Anaphylaxis is a severe, life- Histamine release causes the threatening allergic reaction. It constriction of smooth muscle, occurs when the body releases particularly in the stomach excessive amounts of and lungs, leading to histamine. bronchospasm. Increased Secretions Vasodilation and Edema Histamine release increases Histamine causes vasodilation body secretions, causing and increased capillary symptoms such as excessive permeability, resulting in fluid mucus production and watery leakage from blood vessels, eyes. low blood pressure, and edema. Histamine A Crucial Mediator Diverse Actions Allergic Responses Histamine is a key chemical Histamine's release can cause a Histamine is involved in allergic mediator in the body's range of symptoms such as reactions to allergens like inflammatory response to sneezing, runny nose, itchy pollen, dust mites, and insect various allergens and stimuli. eyes, and skin reactions. stings. H2 Blockers 1 1. Gastric Acid 2 2. Peptic Ulcer Reduction Disease H2 blockers are used H2 blockers are to reduce the effective for treating production of gastric peptic ulcer disease. acid. 3 3. Examples Cimetidine (Tagamet), famotidine (Pepcid), nizatidine (Axid) are some examples of H2 blockers. Antihistamines: Mechanism of Action Blocking Histamine Action Competing for Binding Antihistamines block the action of histamine at Antihistamines compete with histamine for H1 receptor sites. They competitively bind to the binding at unoccupied receptors. The receptors, preventing histamine from binding. antihistamine must be present in a higher concentration than histamine to effectively block its action. Antihistamines: Mechanism of Action (Con Histamine Receptor Binding H1 blockers prevent histamine from binding to histamine receptors, reducing the inflammatory response Block Histamine Actions These drugs effectively block the actions of histamine but do not reverse them. Early Treatment Antihistamines should be administered early in treatment to prevent histamine binding. Antihistamines: Other Effects Skin Anticholinergic Sedative Antihistamines reduce Antihistamines have Some antihistamines can capillary permeability. This anticholinergic effects that cause drowsiness. These are decreases redness and reduce nasal, salivary, and called "first-generation" swelling caused by histamine lacrimal gland secretions. This antihistamines and are often release. They also prevent lessens symptoms like runny prescribed at bedtime due to wheal-and-flare formation and nose, tearing, and itchy eyes. this effect. itching. Antihistamines: Indications Allergic Rhinitis Motion Sickness Parkinson's Disease Allergic Reactions Antihistamines are Antihistamines can Some antihistamines Antihistamines can used to treat allergic help prevent and treat may be used to help help to relieve the rhinitis, a condition motion sickness by manage the tremors symptoms of allergic that causes blocking the effects of and other symptoms of reactions, such as inflammation of the histamine in the inner Parkinson's disease. hives, itching, and nasal passages due to ear. swelling. an allergic reaction. Antihistamines: Contraindications Known Drug Allergy Narrow-Angle Glaucoma Patients should not use Antihistamines can increase antihistamines if they have a intraocular pressure, which can known allergy to the drug. worsen narrow-angle glaucoma. Cardiac Disease, Hypertension Other Contraindications Antihistamines can increase Patients with kidney disease, heart rate and blood pressure, bronchial asthma, chronic which can be dangerous for obstructive pulmonary disease patients with heart disease or (COPD), or who are using hypertension. antihistamines as sole drug therapy during acute asthmatic attacks should avoid these medications. Antihistamines: Contraindications (Cont.) 1 1. Peptic Ulcer Disease 2 2. Seizure Disorders Antihistamines can worsen Some antihistamines can symptoms of peptic ulcer lower the seizure threshold, disease, a condition where increasing the risk of the lining of the stomach or seizures in people with duodenum is damaged. epilepsy. 3 3. Benign Prostatic 4 4. Pregnancy Hyperplasia (BPH) Many antihistamines are not Certain antihistamines can recommended during worsen urinary symptoms in pregnancy, especially in the men with BPH, a condition first trimester, due to where the prostate gland potential risks to the fetus. enlarges. Antihistamines: Adverse Effects Anticholinergic Effects Drowsiness Anticholinergic effects are the most common Drowsiness is another common adverse effect of adverse effects of antihistamines. These effects antihistamines. This can range from mild can include dry mouth, difficulty urinating, drowsiness to deep sleep. constipation, and changes in vision. Antihistamines: Two Types Traditional Antihistamines Nonsedating Antihistamines These older antihistamines cross the blood-brain These newer antihistamines are less likely to cause barrier, leading to sedation and drowsiness as a drowsiness and are commonly used for long-term side effect. treatment of allergies. Nonsedating/Peripherally Acting Antihistamines Sedation Nonsedating antihistamines were developed to avoid sedation and other CNS effects. Peripheral Action These medications work peripherally to block histamine receptors, reducing central nervous system side effects. Duration of Action Longer duration of action promotes compliance, leading to more consistent symptom relief. Traditional Antihistamines Older Medications Central and Peripheral Activity Traditional antihistamines were developed and used These medications block prior to the discovery of histamine receptors in nonsedating both the central nervous antihistamines. system and peripheral tissues. Anticholinergic Effects Examples These medications also Common traditional block acetylcholine antihistamines include receptors, which can lead diphenhydramine, to side effects such as dry brompheniramine, mouth and drowsiness. chlorpheniramine, dimenhydrinate, meclizine, and promethazine. Decongestants: Types Adrenergics Anticholinergics The most common Less frequently used, decongestants, these these medications are medications are parasympatholytics. sympathomimetics. Corticosteroids Topical nasal steroids are used for longer-term relief. Oral Decongestants Duration Potency Oral decongestants Oral decongestants are have a longer duration less potent than topical of action, but their nasal decongestants. effects take longer to appear. Rebound Congestion Drug Class Oral decongestants do Oral decongestants are not cause rebound exclusively adrenergic congestion, unlike medications. topical nasal decongestants. Topical Nasal Decongestants Topical Adrenergics Mechanism of Action Relief Topical adrenergic nasal These drugs constrict blood Topical decongestants provide decongestants are a common vessels in the nasal passages, rapid onset of relief from nasal treatment for nasal congestion. reducing swelling and congestion. congestion. Topical Nasal Decongestants (Cont.) 1 1. Intranasal Steroids 2 2. Anticholinergic These are the most Intranasal effective topical nasal ipratropium is a decongestants. They newer nasal spray. It are a first-line is used to treat treatment for allergic rhinorrhea in patients rhinitis. with the common cold or allergic 3 3. Mechanism of Action rhinitis. Intranasal steroids reduce inflammation and congestion. Ipratropium blocks acetylcholine receptors in the nose. Nasal Decongestants: Mechanism of Action Site of Action Adrenergics Nasal decongestants target blood vessels Adrenergic decongestants stimulate alpha- surrounding nasal sinuses. adrenergic receptors, causing vasoconstriction. This includes the lining of the nose and sinuses. This leads to the shrinkage of swollen tissues and improved drainage. Nasal Decongestants: Mechanism of Action (Cont.) Nasal Steroids Nasal steroids are anti-inflammatory drugs. Immune System These medications reduce inflammation by inhibiting immune system cells. Decreased Congestion Steroids help to decrease congestion in the nose by reducing inflammation. Nasal Decongestants: Indications Acute Rhinitis Chronic Rhinitis Sinusitis Pre-Procedure Use Nasal decongestants These medications can Nasal decongestants Nasal decongestants are commonly used to also be helpful for are often employed to can be used to reduce relieve nasal chronic rhinitis, a alleviate sinus nasal swelling before congestion associated condition that causes congestion and procedures like surgery with acute rhinitis, also long-term nasal pressure related to or nasal endoscopy. known as the common congestion and sinusitis. cold. inflammation. Nasal Decongestants: Contraindications Drug Allergy Narrow-Angle Glaucoma Patients with a known allergy to nasal decongestants Nasal decongestants can increase intraocular should avoid them. pressure, potentially worsening glaucoma. Uncontrolled Cardiovascular Disease Other Contraindications Patients with uncontrolled cardiovascular disease Nasal decongestants are also contraindicated in should use nasal decongestants with caution. patients with diabetes, hyperthyroidism, and a history of cerebrovascular accident or transient ischemic attacks. Nasal Decongestants: Adverse Effects Nervousness Nasal decongestants can lead to nervousness, insomnia, and palpitations due to their effects on the central nervous system. Dryness Topical nasal decongestants can cause local mucosal dryness and irritation. Tremors Excessive doses can lead to systemic effects, including tremors and palpitations, due to adrenergic stimulation of the heart, blood vessels, and central nervous system. Two Basic Types of Cough Productive Cough Nonproductive Cough Productive coughs are also called wet coughs. Nonproductive coughs are also called dry They are associated with phlegm or mucus coughs. These coughs are not associated with production. Phlegm is thick and sticky. It may be phlegm or mucus production. They are often clear or discolored. irritated or scratchy. Antitussives Purpose Types Antitussives are drugs Antitussives are used to stop or reduce categorized as either coughing. opioid or nonopioid. Indications Benefit Antitussives are Antitussives can be typically used for used in cases when nonproductive coughs, coughing is harmful, when coughing is not like with certain productive or helpful. respiratory conditions. Antitussives: Mechanism of Action Opioids Non-Opioids Opioids suppress the cough reflex by acting Non-opioid antitussives, such as directly on the cough center in the medulla. dextromethorphan, work by suppressing the cough reflex in the brainstem. Codeine and hydrocodone are commonly These drugs are effective for treating prescribed opioid antitussives. nonproductive coughs and are generally well- tolerated. Antitussives: Mechanism of Action (Cont.) Nonopioids Dextromethorphan Benzonatate Dextromethorphan and Dextromethorphan works by Benzonatate works by benzonatate are common inhibiting the cough reflex numbing stretch receptors in nonopioid antitussives that pathway in the brain without the respiratory tract, work by suppressing the causing CNS depression or preventing stimulation of the cough reflex. analgesic effects. cough center. Antitussives: Adverse Effects Dizziness Antitussives can sometimes cause dizziness. Sedation Many antitussives can induce drowsiness. Nausea Nausea is a common side effect. Expectorants Drug Action Mechanism of Action Effect Expectorants are drugs that These drugs work by thinning Expectorants aid in the removal help the body remove mucus the mucus, making it easier to of mucus, reducing the from the respiratory system. cough up. symptoms of congestion. Expectorants: Mechanisms of Action 1 1. Reflex Stimulation 2 2. Direct Stimulation Some expectorants Other expectorants irritate the directly stimulate gastrointestinal tract, secretory glands in the causing a reflex respiratory tract, response that loosens increasing fluid and thins respiratory production. secretions. 3 3. Thinner Mucus The ultimate goal of expectorants is to create thinner mucus that is easier to cough up and expel from the body. Expectorants: Drug Effects Sputum Loosening Cough Reduction Expectorants help This indirect effect make thick phlegm helps reduce the need thinner and easier to to cough, easing cough up. discomfort. Improved Breathing By reducing mucus buildup in the airways, breathing becomes easier. Expectorants: Indications Productive Cough Infections Expectorants are helpful in treating They are commonly used to treat coughs that produce mucus. coughs associated with respiratory infections like the common cold or bronchitis. Inflammation Sinusitis Expectorants can also be helpful for They are used for coughs associated coughs caused by inflammation of with chronic paranasal sinusitis. the larynx or pharynx.