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CHAPTER 17 Adrenergic Drugs Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Adrenergic Drugs: Definition Drugs that stimulate the sympathetic nervous system (SNS) Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Adrenergic Drugs: Definition (cont’d) Also known as: Adrenergic agonists Sympathomimetics Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Characteristics Mimic the effects of the SNS neurotransmitters: norepinephrine (NE) epinephrine (EPI) dopamine Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Adrenergic Receptors Located throughout the body Are receptors for the sympathetic neurotransmitters (alpha)-adrenergic receptors (beta)-adrenergic receptors Dopaminergic receptors: respond only to dopamine Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. -Adrenergic Receptors Divided into 1 and 2 receptors Differentiated by their location on nerves Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. 1-Adrenergic Receptors Located on postsynaptic effector cells (the cell, muscle, or organ that the nerve stimulates) Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. 2-Adrenergic Receptors Located on presynaptic nerve terminals (the nerve that stimulates the effector cells) Control the release of neurotransmitters Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Predominant -Adrenergic Agonist Responses Vasoconstriction CNS stimulation Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. -Adrenergic Receptors All are located on postsynaptic effector cells 1-adrenergic receptors—located primarily in the heart 2-adrenergic receptors—located in smooth muscle of the bronchioles, arterioles, and visceral organs Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. -Adrenergic Agonist Response Results in: Bronchial, GI, and uterine smooth muscle relaxation Glycogenolysis Cardiac stimulation Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Dopaminergic Receptors An additional adrenergic receptor Stimulated by dopamine Causes dilation of the following blood vessels, resulting in increased blood flow Renal Mesenteric Coronary Cerebral Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Responses to Stimulation Location Receptor Response Cardiac muscle 1 2 1 AV Node 1 SA Node 1 Constriction Dilation Increased contractility Increased heart rate Increased heart rate Cardiovascular: Blood vessels Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Responses to Stimulation (cont’d) Location Receptor Response Gastrointestinal: Muscle 2 Sphincters 1 Decreased motility Constriction Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Responses to Stimulation (cont’d) Location Genitourinary: Bladder sphincter Penis Uterus Receptor Response 1 Constriction 1 1 2 Ejaculation Contraction Relaxation Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Responses to Stimulation (cont’d) Location Receptor Response Respiratory: Bronchial muscles 2 Dilation Liver 2 Glycogenolysis Pupils 1 Dilation Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Catecholamines Substances that can produce a sympathomimetic response Endogenous epinephrine, norepinephrine, dopamine Synthetic dobutamine, phenylephrine Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mechanism of Action Direct-acting sympathomimetic Binds directly to the receptor and causes a physiologic response Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mechanism of Action (cont’d) Indirect-acting sympathomimetic Causes the release of catecholamine from the storage sites (vesicles) in the nerve endings The catecholamine then binds to the receptors and causes a physiologic response Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mechanism of Action (cont’d) Mixed-acting sympathomimetic Directly stimulates the receptor by binding to it and Indirectly stimulates the receptor by causing the release of stored neurotransmitters from the vesicles in the nerve endings Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Drug Effects Stimulation of -adrenergic receptors on smooth muscles results in: Vasoconstriction of blood vessels Relaxation of GI smooth muscles Contraction of the uterus and bladder Male ejaculation Decreased insulin release Contraction of the ciliary muscles of the eye (dilated pupils) Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Drug Effects (cont’d) Stimulation of 1-adrenergic receptors on the myocardium, AV node, and SA node results in cardiac stimulation Increased force of contraction (positive inotropic effect) Increased heart rate (positive chronotropic effect) Increased conduction through the AV node (positive dromotropic effect) Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Drug Effects (cont’d) Stimulation of 2-adrenergic receptors on the airways results in: Bronchodilation (relaxation of the bronchi) Other effects of 2-adrenergic stimulation: Uterine relaxation Glycogenolysis in the liver Increased renin secretion in the kidneys Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Indications Bronchodilators: treatment of asthma and bronchitis Drugs that stimulate 2-adrenergic receptors of bronchial smooth muscles, causing relaxation, resulting in bronchodilation Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. 2-Adrenergic Drugs Examples: albuterol epinephrine levalbuterol metaproterenol Others ephedrine isoetharine salmeterol terbutaline* * Used to stop premature labor—causes relaxation of uterine smooth muscle Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Indications (cont’d) Reduction of intraocular pressure and causes mydriasis (pupil dilation): treatment of openangle glaucoma or 2 receptors, or both – Examples: epinephrine and dipivefrin Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Indications (cont’d) Temporary relief of conjunctival congestion (eyes) -adrenergic receptors Examples: – epinephrine – phenylephrine – naphazoline – tetrahydrozoline Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Indications (cont’d) Nasal decongestant Intranasal (topical) application causes constriction of dilated arterioles and reduction of nasal blood flow, thus decreasing congestion 1-adrenergic stimulation Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Topical Nasal Decongestants Examples: naphazoline tetrahydrozoline epinephrine ephedrine phenylephrine Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Vasoactive Sympathomimetics (Pressors, Inotropes) Also called cardioselective sympathomimetics Used to support the heart during cardiac failure or shock; various and receptors affected Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Vasoactive Sympathomimetics (Pressors, Inotropes) (cont’d) Examples: dobutamine ephedrine fenoldopam methoxamine Others dopamine epinephrine phenylephrine norepinephrine Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. -Adrenergic Adverse Effects CNS Headache, restlessness, excitement, insomnia, euphoria Cardiovascular Palpitations (dysrhythmias), tachycardia, vasoconstriction, hypertension Other Loss of appetite, dry mouth, nausea, vomiting, taste changes (rare) Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. -Adrenergic Adverse Effects CNS Mild tremors, headache, nervousness, dizziness Cardiovascular Increased heart rate, palpitations (dysrhythmias), fluctuations in BP Other Sweating, nausea, vomiting, muscle cramps Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Interactions Anesthetic drugs Tricyclic antidepressants MAOIs Antihistamines Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Interactions (cont’d) Thyroid preparations Antihypertensives Will directly antagonize another adrenergic drug, resulting in reduced effects Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications Assess for allergies and history of hypertension, cardiac dysrhythmias, or other cardiovascular disease Assess renal, hepatic, and cardiac function before treatment Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d) Perform baseline assessment of vital signs, peripheral pulses, skin color, temperature, and capillary refill; include postural blood pressure and pulse Follow administration guidelines carefully Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d) Intravenous administration Check IV site often for infiltration Use clear IV solutions Use an infusion pump Infuse drug slowly to avoid dangerous cardiovascular effects Monitor cardiac rhythm Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d) With chronic lung disease: Instruct patients to avoid factors that exacerbate their condition Encourage fluid intake (up to 3000 mL per day) if permitted Educate about proper dosing, use of equipment (MDI, spacer, nebulizer), and equipment care Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d) Salmeterol is indicated for prevention of bronchospasms, not management of acute symptoms Overuse of nasal decongestants may cause rebound nasal congestion or ulcerations Avoid OTC or other medications because of possible interactions Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d) Administering two adrenergic drugs together may precipitate severe cardiovascular effects such as tachycardia or hypertension Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d) Monitor for therapeutic effects: (cardiovascular uses) Decreased edema Increased urinary output Return to normal vital signs Improved skin color and temperature Increased LOC Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc. Nursing Implications (cont’d) Monitor for therapeutic effects (asthma): Return to normal respiratory rate Improved breath sounds, fewer crackles Increased air exchange Decreased cough Less dyspnea Improved blood gases Increased activity tolerance Mosby items and derived items © 2007, 2005, 2002 by Mosby, Inc., an affiliate of Elsevier Inc.
