Summary

This document provides lecture notes on respiratory and gastrointestinal drugs. It covers various drugs, their mechanisms of action, and side effects.

Full Transcript

Respiratory and Gastrointestinal Drugs Marilyn Odom, Ph.D. Objectives 1. Match indication with drug classes. 2. List brand and generic names for prototypical drugs in each class. 3. Discuss mechanism of action for each drug class. 4. Discuss primary side effects of each drug class and include...

Respiratory and Gastrointestinal Drugs Marilyn Odom, Ph.D. Objectives 1. Match indication with drug classes. 2. List brand and generic names for prototypical drugs in each class. 3. Discuss mechanism of action for each drug class. 4. Discuss primary side effects of each drug class and include mechanism if relevant. 5. Describe the route of administration of drugs. 6. Discuss drugs of choice for specific diseases. 7. Discuss any drug interactions stressed during class. Respiratory Drugs Antitussives Suppress coughing associated with common cold Short-term use for dry cough Wet, productive coughs expectorate secretions (GOOD) Example Benzonatate (Tessalon)—anesthetic effect on respiratory mucosa Codeine—inhibits cough reflex by acting on the brainstem cough center Dextromethorphan—non-narcotic that inhibits cough reflex Diphenhydramine--antihistamine Hydrocodone Hydromorphone Primary side effect—sedation Decongestants Bind to alpha 1 receptors in blood vessels in nasal mucosa to cause vasoconstriction Administered orally or nasal spray Examples Phenylephrine (Sudafed PE) Pseudoephedrine (Chlor Trimeton; Sudafed) Oxymetazoline (Afrin) Primary side effects Elevated BP Headache Dizziness Nervousness Antihistamines Antagonists at histamine receptors Four histamine receptors in body H1—vascular, respiratory, and other tissues—allergic reactions, respiratory infections H2—GI tract—regulates gastric acid secretion H3—sleep, cognitive function, pain modulation H4—important in mediating inflammation (asthma, allergic rhinitis, etc) Antihistamines antagonize H1 Antihistamines Adverse effects Sedation Anticholinergic effects (dry mouth, dry eyes, tachycardia, urinary retention) Dizziness GI distress Hypotension First generation Diphenhydramine (Benadryl); chlorpheniramine Cross BBB Sedation and psychomotor slowing Second generation Limited crossing of BBB More selective for H1 Antihistamines Second generation antihistamines Cetirizine (Zyrtec) Desloratadine (Clarinex) Fexofenadine (Allegra) Loratadine (Claritin) Mucolytics & Expectorants Mucolytics – drugs Helps prevent thick mucus from blocking respiratory that decrease the pathways viscosity of the Used to treat pneumonia, COPD Acetylcysteine secretions Expectorants - Guaifenesin is the only expectorant approved by the FDA Facilitate the Helps prevent thick mucus from blocking respiratory production and pathways Used to treat pneumonia, COPD removal of mucus Mucoactive agents Drugs for obstructive pulmonary disease Obstructive pulmonary disease Symptoms include bronchospasm, airway inflammation, and mucous plugging Goal of medications is to prevent or reverse bronchial constriction and obstruction of the airways by using bronchodilators and anti-inflammatory agents Bronchodilators: Beta-adrenergic agonists Xanthine derivatives Anticholinergics Anti-inflammatory agents Glucocorticoids Beta-adrenergic agents Respiratory smooth muscle cells have beta-2 adrenergic receptors When they are stimulated relaxation of the bronchial smooth muscle occurs Beta-adrenergic agonists stimulate these receptors, so they cause bronchodilation to occur These drugs can be used to prevent airway obstruction in bronchospastic diseases Some of these drugs are selective and some are not Selective drugs only stimulate the beta-2 receptors Nonselective will stimulate beta-1 and beta-2 receptors Nonselective drugs will cause increased side effects – beta-1 receptors are found on the myocardium Beta-adrenergic agents They can be administered orally, subcutaneously, or by inhalation Inhalation is preferred method Less side effects because the drug is not getting into the systemic circulation Action of onset is more rapid Metered-dose inhalers are can also be used for administration If not used properly then the drug may not be properly delivered Spacers can be used to ensure adequate delivery Beta-adrenergic agents Another method of administration is using a nebulizer Device that mixes the drug with air to make a mist that is then inhaled through a mask Adverse effects Prolonged use can cause tolerance Cardiac irregularities if beta-1 receptors are stimulated Stimulation of receptors in the CNS: nervousness, restlessness, and tremor Beta-adrenergic agents Examples: Albuterol (Ventolin) Beta-2 receptor Inhaled Levalbuterol (Xopenex) Beta-2 receptor Inhaled Salmeterol (Serevent) Beta-2 receptor Inhaled Xanthine Derivatives Chemically similar compounds – theophylline, caffeine, and theobromine Theophylline is also used to treat airway obstruction because it can produce bronchodilation Debate on exactly how the bronchodilation occurs Examples: Aminophylline Dyphylline Theophylline Adverse Effects: Toxicity: therapeutic and toxic range blood levels can have some overlap. Early signs of toxicity: nausea, confusion, irritability, and restlessness Cardiac arrhythmias and fatal seizures can occur Anticholinergic drugs Lungs have extensive parasympathetic innervation from the vagus nerve Efferent fibers of the vagus nerve release acetylcholine onto respiratory smooth muscle cells which have muscarinic cholinergic receptors If these receptors are stimulated, then bronchoconstriction will occur Anticholinergic drugs block muscarinic cholinergic receptors and prevent acetylcholine induced bronchoconstriction End result is bronchodilation Often the drug of choice in treating COPD Anticholinergic drugs In COPD the increased bronchoconstriction appears to be due to increased vagal tone and acetylcholine release By reducing the effects of acetylcholine then bronchoconstriction can be better controlled Side Effects: “can’t see, can’t pee, can’t poop” Dry mouth Constipation Urinary retention Tachycardia Blurry vision confusion Glucocorticoids AKA: corticosteroids Powerful anti-inflammatory drugs Control inflammation induced bronchospasm Most effective drugs at controlling asthma Can be given via IV in acute attacks of bronchoconstriction Can also be given via inhaler or orally Adverse effects are limited when these drugs are given via inhaler and are not absorbed into the systemic circulation Patients should rinse their mouths after using these to reduce the risk of oral irritation Glucocorticoids AKA: corticosteroids Adverse Effects Osteoporosis Skin breakdown Muscle wasting Retardation of growth in children Cataracts Glaucoma Hyperglycemia Aggravation of diabetes mellitus and HTN Examples: Budesonide (Pulmicort) Cortisone (Cortone) Prednisone (Sterapred) Cromolyn sodium Helps to prevent bronchospasm in people with asthma Will NOT reverse it Must be taken before patients undertakes/or is exposed to specific activity or substance (pet) that induces attack Inhalational Can prevent allergic rhinitis associated with seasonal allergies Leukotriene inhibitors Inflammatory compounds that are used to control airway inflammation with bronchoconstrictive disease Can be combined with glucocorticoids and beta agonists to provide better management of COPD and asthma Montelukast (Singulair) Adverse Effects Rare causes of liver toxicity Asthma Disease of the respiratory system with bronchial smooth muscle spasm, airway inflammation, and mucous plugging Patients have an exaggerated bronchoconstrictor response of the airway to various stimuli Glucocorticoids are the first line of defense for long term management Many of these can now be given via inhalation so the risk of systemic side effects is very low Greatly reduce the inflammation that underlies asthma whereas bronchodilators just treat the secondary manifestations Can be combined with beta-2 agonists to provide optimal results Some medications are sold as a combination of these 2: Advair, Advair Diskus, Symbicort Asthma Short acting beta-2 agonists are the best choice for treating symptomatic asthma attacks Leukotriene inhibitors can also be used to control inflammation in asthma Summary: Inhaled glucocorticoids are the main tx for asthma Leukotriene inhibitors, beta agonists, and theophylline can be used as supplements COPD Drug therapy for COPD is directed at maintaining airway patency and preventing airflow restriction Anticholinergics are often the first drugs used Long-acting beta-2 agonists are also used to promote bronchodilation Cystic Fibrosis Pharmacological management is focused on maintaining airway patency Bronchodilators and mucolytic and/or expectorant drugs may help limit the formation of mucus plugs Systemic glucocorticoids can also be useful (prednisone) at limiting airway inflammation and improving pulmonary function Gastrointestinal GI Drugs GI tract is responsible for food digestion and the absorption of water and nutrients The acid in the gastric juices is necessary in order to activate digestive activity and controlling bacteria The gastric acid can cause severe ulceration and hemorrhage of the stomach lining if production is excessive or if normal stomach mucosa is disturbed (drugs, bacterial infections) Drugs are available to work to control or limit the gastric acid in the stomach Antacids H2 receptor blockers Proton pump inhibitors Antacids Neutralize stomach acids Many different compositions exist: Aluminum hydroxide – can cause constipation Magnesium hydroxide – can cause diarrhea Calcium carbonate Combination of the above Electrolyte imbalances can occur when used in high doses These drugs alter the gastric pH which can impact the pharmacokinetics of other drugs – medications that rely on stomach acidity to dissolve or activate the drug Antacids should NOT be taken within 2 hours of other orally administered drugs – especially antibiotics, digoxin, warfarin, iron supplements H2 receptor blockers Gastric acid secretions is regulated by many endogenous chemicals including histamines Histamine stimulates stomach cells to increase gastric acid secretion – these are called H2 receptors H2 blockers bind to the receptors without activating them This prevents the histamine activated release of gastric acid Used in the acute and long-term management of peptic ulcer and other problems such as GERD Examples: Cimetidine (Tagament) Famotidine (Pepcid) Rantidine (Zantac) H2 receptor blockers Side Effects Headache Dizziness Mild, transient GI problems – diarrhea, constipation, nausea Arthralgia, myalgias Tolerance can occur with continuous daily use – so often its recommended to take them every other day Proton pump inhibitors Inhibit the H+/K+ ATP pump that is responsible for secreting acid from gastric parietal cells into the stomach PPIs can reduce gastric secretions by 80-95% Drug of choice in long term management of those with gastric and duodenal ulcers and GERD Prescription and non-prescription forms Adverse effects: Gastric acid rebound can occur when they are discontinued after being used for a long time Long term use is associated with gastric polyps which could lead to GI tumors Affect calcium metabolism leading to decreased bone mineralization and risk of fractures Proton pump inhibitors Examples: Esomeprazole (Nexium) Lansoprazole (Prevacid) Omeprazole (Prilosec) All of these are used in the management of GERD and gastric or duodenal ulcers Other GI Drugs To treat diarrhea drugs that inhibit excessive peristalsis are used Opioid derivatives Decreased motility or constipation Commonly occurs in those who have been on bedrest is treated with laxatives Can be a problem in those with spinal cord injuries In general GI drugs are well tolerated and will not limit a patient’s participation in rehabilitation Laxatives Promotes evacuation of the bowel Cathartics promote lower GI exit and is more rapid than laxatives May be needed in patients On prolonged bed rest Spinal cord injury Types of laxatives Bulk-forming—absorb water, swell, stretches bowel, stimulates peristalsis (bran, Metamucil) Stimulants—MOA ?; Senokot, Dulcolax Hyperosmotic—draws water into intestines to increase stool fluid content and stimulate peristalsis (MOM, Miralax) Lubricants and stool softeners—facilitate entry of water into fecal mass to soften stool and promote defecation (Colace, mineral oil) Laxatives Adverse effects Nausea and cramping With prolonged use Dehydration and electrolyte abnormalities Emetics and antiemetics Emetics—induce vomiting Antiemetics-decreases N/V

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