UNBC-Pharm Topic 7 Adrenergics PDF

Topic 7. Autonomic Nervous System: Adrenergics NRSG-303-A1  Objectives: 1. Briefly describe the functions of the sympathetic nervous system and the specific effects of adrenergic stimulation. 2. List the various drugs classified as adrenergic agonists or sympathomimetics. 3. Discuss t...

Topic 7. Autonomic Nervous System: Adrenergics NRSG-303-A1  Objectives: 1. Briefly describe the functions of the sympathetic nervous system and the specific effects of adrenergic stimulation. 2. List the various drugs classified as adrenergic agonists or sympathomimetics. 3. Discuss the mechanisms of action, therapeutic effects, indications, adverse and toxic effects, cautions, contraindications, interactions, and available antidotes to overdosage of the adrenergic agonists or sympathomimetics. 4. List the various drugs categorized as adrenergic antagonists (blockers) or sympatholytics. 5. Discuss the mechanisms of action, therapeutic effects, indications, adverse and toxic effects, cautions, contraindications, drug interactions, dosages, routes of administration, and any antidotal management for the alpha-antagonists (blockers), nonselective beta blockers, and beta1- and beta2-blockers. 6. Develop a collaborative plan of care that includes all phases of the nursing process for patients taking adrenergic antagonists. Peripheral Nervous System Adrenergic Drugs Drugs that stimulate the sympathetic nervous system (SNS) Adrenergic agonists Also known as Sympathomimetics norepinephrine Mimic the effects of SNS epinephrine neurotransmitters (catecholamines) dopamine  Adrenergic Receptors α-Adrenergic receptors ß1-Adrenergic receptors: located primarily in the heart α1-Adrenergic receptors Located on postsynaptic effector cells ß2-Adrenergic receptors: located in smooth (the cell, muscle, or organ the nerve stimulates) muscle of the bronchioles, arterioles, and α2-Adrenergic receptors visceral organs Located on presynaptic nerve terminals (the nerve that stimulates the effector cells) Control the release of neurotransmitters ß-Adrenergic receptors  Substances that can produce a sympathomimetic response Catecholamines Endogenous epinephrine, norepinephrine, dopamine Synthetic dobutamine, phenylephrine hydrochloride Mechanism of Action Direct-acting sympathomimetic Binds directly to the receptor and causes a physiological response Indirect-acting sympathomimetic Causes release of catecholamine from storage sites (vesicles) in nerve endings Catecholamine then binds to receptors and causes a physiological response.  Stimulation of α-adrenergic receptors on smooth muscles results in: Vasoconstriction of blood vessels Relaxation of GI smooth muscles (decreased motility) Drug Effects Constriction of bladder sphincter Contraction of uterus Male ejaculation Contraction of pupillary muscles of the eye (dilated pupils)  Stimulation of ß1-adrenergic receptors on the myocardium, atrioventricular (AV) node, and sinoatrial node results in cardiac stimulation. Increased force of contraction (positive Drug Effects inotropic effect) Increased heart rate (positive chronotropic effect) Increased conduction through AV node (positive dromotropic effect)  Stimulation of ß2-adrenergic receptors on the airways results in bronchodilation (relaxation of the bronchi). Other effects of ß2-adrenergic stimulation: Drug Effects Uterine relaxation Glycogenolysis in the liver Increased renin secretion in the kidneys Relaxation of GI smooth muscles (decreased motility)  Treatment of asthma and bronchitis Bronchodilators: drugs that stimulate ß2- adrenergic receptors of bronchial smooth muscles, causing relaxation, resulting in bronchodilation Indications Common bronchodilators that are classified as predominantly β2-selective adrenergic drugs formoterol fumurate dihydrate, salbutamol, salmeterol, xinafoate, and terbutaline sulphate.  Temporary relief of conjunctival congestion (eyes) α-Adrenergic receptors Examples: epinephrine, naphazoline hydrochloride, phenylephrine hydrochloride, Indications tetrahydrozoline Reduction of intraocular pressure and dilation of pupils: treatment of open-angle glaucoma α-Adrenergic receptors Example: dipivefrin hydrochloride  Also called cardioselective sympathomimetics Used to support the heart during cardiac failure or shock; various α- and ß-receptors affected Vasoactive Exampes Sympathomimetics dobutamine (Pressors, Inotropes) dopamine midodrine epinephrine phenylephrine norepinephrine  Naturally occurring catecholamine neurotransmitter Potent dopaminergic as well as ß1- and α1-adrenergic receptor activity dopamine hydrochloride Low dosages: can dilate blood vessels in the brain, heart, kidneys, and mesentery, which increases blood flow to these areas (dopaminergic receptor activity) Higher infusion rates: improve cardiac contractility and output (ß 1- adrenergic receptor activity) Highest doses: vasoconstriction (α1-adrenergic receptor activity) epinephrine hydrochloride (Adrenalin®) Endogenous vasoactive catecholamine Acts directly on both the α- and ß-adrenergic receptors of tissues innervated by the SNS Prototypical nonselective adrenergic agonist Administered in emergency situations One of the primary vasoactive drugs used in many advanced cardiac life support protocols  Stimulates α-adrenergic receptors Causes vasoconstriction Direct-stimulating ß-adrenergic effects on the norepinephrine heart (ß1-adrenergic receptors) betartrate No stimulation to ß2-adrenergic receptors of the (Levophed®) lung Treatment of hypotension and shock Administered by continuous infusion  CNS Headache, restlessness, excitement, insomnia, euphoria α-Adrenergic Cardiovascular Adverse Effects Palpitations (dysrhythmias), tachycardia, vasoconstriction, hypertension Other Loss of appetite, dry mouth, nausea, vomiting, taste changes (rare)  CNS Mild tremors, headache, nervousness, dizziness, insomnia, euphoria ß-Adrenergic Cardiovascular Adverse Effects Chest pain, increased heart rate, palpitations (dysrhythmias), hypertension, vasoconstriction Other Sweating, nausea, vomiting, muscle cramps  Anaesthetic drugs Digoxin Interactions Tricyclic antidepressants Monoamine oxidase inhibitors (MAOIs) Antihistamines Thyroid preparations Nursing Implications Complete a comprehensive health history. Assess for allergies and asthma; take history of hypertension, cardiac dysrhythmias, and other cardiovascular disease. Assess renal, hepatic, and cardiac function before treatment. Perform baseline assessment Monitor for therapeutic effects (cardiovascular uses) Decreased edema Increased urinary output Return to normal vital signs Improved skin colour and temperature Pedal pulse intact and strong to palpation  Adrenergic Blockers Bind to adrenergic receptors but inhibit or block stimulation of the sympathetic nervous system (SNS) Have the opposite effect of adrenergic drugs Inhibit (lyse) sympathetic stimulation Also known as: Adrenergic antagonists Sympatholytics α-blockers, β-blockers, and α-β–blockers Classified by the type of adrenergic receptor they block α1- and α2-receptors β1- and β2-receptors  Cause both arterial and venous dilation, reducing peripheral vascular resistance Drug Effects and blood pressure (BP) and Used to treat hypertension Indications: Effect on receptors on prostate gland and bladder decreases resistance to α-Blockers urinary outflow, thus reducing urinary obstruction and relieving the effects of benign prostatic hyperplasia (BPH). α-Blockers: Adverse Effects Body system/adverse effects Cardiovascular: Palpitations, orthostatic hypotension, tachycardia, edema, chest pain Central nervous system: Dizziness, headache, anxiety, depression, weakness, numbness, fatigue Gastrointestinal: Nausea, vomiting, diarrhea, constipation, abdominal pain Other: Incontinence, dry mouth, pharyngitis  doxazosin, prazosin, and terazosin Block α1-adrenergic receptors Peripherally When α1-adrenergic receptors are blocked, BP is decreased. Acting α1- Dilate arteries and veins Blockers α1-Blockers also increase urinary flow rates and decrease outflow obstruction by preventing smooth muscle contractions in the bladder neck and urethra. Use: benign prostatic hyperplasia (BPH) tamsulosin (Flomax®) α-Blocker used primarily to treat BPH; exclusively indicated for male patients Contraindications: known drug allergy and concurrent use of erectile dysfunction drugs such as sildenafil Adverse effects: headache, abnormal ejaculation, rhinitis, and others  Block stimulation of β-receptors in the SNS Compete with norepinephrine and epinephrine Can be selective or nonselective Cardioselective β-blockers or β1-blocking β-Blockers drugs Nonselective β-blockers block both β1- receptors and β2-receptors. β2-Receptors are located primarily on the smooth muscles of the bronchioles and blood vessels.  β1-Receptors Located primarily on the heart β-Blockers selective for these receptors are called cardioselective β-blockers. β-Receptors β2-Receptors Located primarily on smooth muscle of bronchioles and blood vessels  Cardioselective β-blockers (β1) β-Receptors: Reduce SNS stimulation of the heart Decrease heart rate Mechanism of Prolong sinoatrial node recovery Action Slow conduction rate through the atrioventricular (AV) node Decrease myocardial contractility, thus reducing myocardial oxygen demand  Nonselective β-blockers (β1 and β2) Cause same effects on heart as do cardioselective ß-blockers β-Receptors: Constrict bronchioles, resulting in Mechanism of narrowing of airways and shortness of Action (2 of 2) breath Produce vasoconstriction of blood vessels Other effects β-Receptors: Indications Angina, MI, hypertension Decrease demand for myocardial oxygen Cardioprotective Inhibit stimulation from circulating catecholamines Dysrhythmias Glaucoma (topical use) Migraine headache Lipophilicity allows entry into central nervous system. β-Blockers: Adverse Effects Nonselective β-blockers may interfere with normal responses to hypoglycemia (tremor, tachycardia, nervousness). May mask signs and symptoms of hypoglycemia Use with caution in patients with diabetes mellitus.  acebutolol (Sectral®) atenolol (Tenormin®) bisoprolol fumerate Cardioselective esmolol (Brevibloc®) β-Blockers nebivolol (Bystolic®) metoprolol (Lopressor®)  Propranolol, Metoprolol, and Atenolol Reduction of the heart rate through β1-receptor blockade Cause reduced secretion of renin Long-term use causes reduced peripheral vascular resistance. ß-Blockers Dual Action Beta Blocker: labetalol Dual antihypertensive effects of reduction in heart rate (β1- receptor blockade) and vasodilation (α1-receptor blockade) Nursing interventions: Apical pulse and BP. Monitor for side effects (ED is common amongst male patients) decreased HR Atenolol (Tenormin®) Cardioselective β-blocker Commonly used to prevent future heart attacks in patients who have had one attack Hypertension and angina Management of thyrotoxicosis to help block the symptoms of excessive thyroid activity Available for oral use Adrenergic-Blocking Drugs: Nursing Implications Any pre-existing condition that might be Assess for allergies and perform a exacerbated by the use of these drugs thorough cardiac assessment. might be a contraindication to their use. Remember that α-blockers may precipitate hypotension (first dose effect). Remember that some β-blockers may precipitate bradycardia, hypotension, heart block, heart failure, and bronchoconstriction.  Avoid over-the-counter medications because of possible interactions. Adrenergic- Possible drug interactions may occur Blocking Drugs: with: Nursing Antacids (aluminum hydroxide type) Implications Antimuscarinics or anticholinergics Diuretics and cardiovascular drugs Neuromuscular blocking drugs Oral hypoglycemic drugs  Encourage patients to take medications Adrenergic- as prescribed. Blocking Instruct patients that these medications Drugs: should never be stopped abruptly. Nursing Inform patients to report constipation or Implications the development of urinary hesitancy or bladder distention.  Teach patients to change positions slowly to prevent or minimize postural hypotension. Adrenergic- Instruct patients to avoid caffeine (causes Blocking excessive irritability). Drugs: Instruct patients to avoid alcohol ingestion and hazardous activities until blood levels Nursing become stable. Implications Instruct patients to notify their physicians if palpitations, dyspnea, nausea, or vomiting occurs. β-Blocking Drugs: Nursing Implications Monitor for heart rate before administration Rebound hypertension or chest pain may occur if these medications are discontinued abruptly. Instruct patients to notify their physicians if they become ill and are unable to take medication. Inform patients that they may notice a decrease in tolerance for exercise (dizziness and fainting may occur with increased activity), and have patients notify their physicians if these problems occur.  Inform patients to report the following to their physicians: β-Blocking Weight gain of more than 1 kg in 24 hours Drugs: or 2.3 kg in 1 week Nursing Edema of the feet or ankles Implications Shortness of breath Excessive fatigue or weakness Syncope or dizziness Case Study ACCESS THE HANDOUT TITLED “CASE STUDY 1” AND COMPLETE IT IN YOUR ASSIGNED GROUP.  Objectives: 1. Briefly describe the functions of the sympathetic nervous system and the specific effects of adrenergic stimulation. 2. List the various drugs classified as adrenergic agonists or sympathomimetics. 3. Discuss the mechanisms of action, therapeutic effects, indications, adverse and toxic effects, cautions, contraindications, interactions, and available antidotes to overdosage of the adrenergic agonists or sympathomimetics. 4. List the various drugs categorized as adrenergic antagonists (blockers) or sympatholytics. 5. Discuss the mechanisms of action, therapeutic effects, indications, adverse and toxic effects, cautions, contraindications, drug interactions, dosages, routes of administration, and any antidotal management for the alpha-antagonists (blockers), nonselective beta blockers, and beta1- and beta2-blockers. 6. Develop a collaborative plan of care that includes all phases of the nursing process for patients taking adrenergic antagonists.