Drugs Affecting Autonomic Nervous System 1

Lecture objectives Identify the anatomy of nervous system. Identify the drugs that effect ANS

Nervous System Divisions

Nervous System Overview Brain Spinal cord Nerves Functions of nervous system Regulates and coordinates all body activities Center of all mental activity, including thought, learning, and memory

Nervous System Divisions Central Nervous System (CNS) Brain Spinal Cord Processes and stores sensory and motor information Controls consciousness Peripheral Nervous System (PNS) 12 Pairs of Cranial Nerves 31 Pairs of Spinal Nerves Transmits sensory and motor impulses back and forth between CNS and rest of body

Peripheral Nervous System Somatic Nervous System (SNS) Provides voluntary control over skeletal muscle contractions Autonomic Nervous System (ANS) Provides involuntary control over smooth muscle, cardiac muscle, and glandular activity and secretions in response to the commands of the central nervous system

Autonomic Nervous System Sympathetic nerves Increase heart rate Constrict blood vessels Raise blood pressure Fight-or-flight response Parasympathetic nerves Slow heart rate Increase peristalsis of intestines Increase glandular secretions Relax sphincters

Catecholamines Substances that can produce a sympathomimetic response Endogenous: Dopamine (Dopaminergic) epinephrine & norepinephrine (Adrenegeric) 2. Synthetic: isoproterenol, dobutamine, phenylephrine

Fight or Flight Response: These catecholamine hormones facilitate immediate physical reactions These include the following: Acceleration of heart and lung action･Inhibition of stomach and intestinal action Constriction of blood vessels in many parts of the body Dilation of blood vessels for muscles Inhibition of tear glands and salivation Dilation of pupil Relaxation of bladder Inhibition of erection

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

Adrenergic Agents Drugs that stimulate the sympathetic nervous system (SNS) Also known as: adrenergic agonists or sympathomimetics Mimic the effects of the SNS neurotransmitters: norepinephrine (NE) and epinephrine (EPI)

Adrenergic Receptors Located throughout the body Are receptors for the sympathetic neurotransmitters Alpha-adrenergic receptors: respond to NE Beta-adrenergic receptors: respond to EPI

Types of -adrenergic receptor -adrenergic receptors are adrenergic receptors that respond to norepinephrine and to such blocking agents as phenoxybenzamine. They are subdivided into two types: 1, found in smooth muscle, heart, and liver, with effects including vasoconstriction, intestinal relaxation, uterine contraction and pupillary dilation, 2, found in platelets, vascular smooth muscle, nerve termini, and pancreatic islets, with effects including platelet aggregation, vasoconstriction, and inhibition of norepinephrine release and of insulin secretion.

-receptor types -adrenergic receptors respond particularly to epinephrine and to such blocking agents as propranolol. There are three known types of beta receptor, designated β1, β2 and β3. β1-Adrenergic receptors are located mainly in the heart. β2-Adrenergic receptors are located mainly in the lungs, gastrointestinal tract, liver, uterus, vascular smooth muscle, and skeletal muscle. β3-receptors are located in fat cells.

What do the receptors do What do the receptors do? Activation of  receptors leads to smooth muscle contraction Activation of 2 receptors leads to smooth muscle relaxation Activation of 1 receptors leads to smooth muscle contraction (especially in heart)

Clinical Utility of drugs which affect the adrenergic nervous system: a. Agonists of the 2 receptors are used in the treatment of asthma (relaxation of the smooth muscles of the bronchi) b. Antagonists of the 1 receptors are used in the treatment of hypertension and angina (slow heart and reduce force of contraction) c. Antagonists of the 1 receptors are known to cause lowering of the blood pressure (relaxation of smooth muscle and dilation of the blood vessels)

Drug Effects of Adrenergic Agents Stimulation of alpha-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)

Drug Effects of Adrenergic Agents Stimulation of beta2-adrenergic receptors on the airways results in: Bronchodilation (relaxation of the bronchi) Uterine relaxation Glycogenolysis in the liver

Drug Effects of Adrenergic Agents Stimulation of beta1-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) automaticity

Adrenergic Agents: Therapeutic Uses Anorexiants: adjuncts to diet in the short-term management of obesity Examples: benzaphetamine phentermine dextroamphetamine Dexedrine 2.Bronchodilators: treatment of asthma and bronchitis Agents that stimulate beta2-adrenergic receptors of bronchial smooth muscles causing relaxation Examples: albuterol ephedrine epinephrine isoetharine isoproterenol levalbuterol metaproterenol salmeterol terbutaline

Adrenergic Agents: Therapeutic Uses 3. Reduction of intraocular pressure and mydriasis (pupil dilation): treatment of open-angle glaucoma Examples: epinephrine and dipivefrin 4. Nasal decongestant: Intranasal (topical) application causes constriction of dilated arterioles and reduction of nasal blood flow, thus decreasing congestion. Examples: epinephrine ephedrine naphazoline phenylephrine tetrahydrozoline

5. Ophthalmic relieving conjunctival congestion. Examples: epinephrine naphazoline phenylephrine tetrahydrozoline 6. Vasoactive sympathomimetics also called cardio selective sympathomimetics Used to support the heart during cardiac failure or shock. Examples: dobutamine dopamine ephedrine epinephrine fenoldopam isoproterenol methoxamine norepinephrine phenylephrine

Adrenergic Agents: Side Effects Alpha-Adrenergic Effects CNS: headache, restlessness, excitement, insomnia, euphoria Cardiovascular: palpitations (dysrhythmias), tachycardia, vasoconstriction, hypertension Other: anorexia, dry mouth, nausea, vomiting, taste changes (rare)

Adrenergic Agents: Side Effects Beta-Adrenergic Effects CNS: mild tremors, headache, nervousness, dizziness Cardiovascular: increased heart rate, palpitations (dysrhythmias), fluctuations in BP Other: sweating, nausea, vomiting, muscle cramps

Adrenergic Agents: Nursing Implications Assess for allergies and history of hypertension, cardiac dysrhythmias, or other cardiovascular disease. Assess renal, hepatic, and cardiac function before treatment. Perform baseline assessment of vital signs, peripheral pulses, skin color, temperature, and capillary refill. Include postural blood pressure and pulse. Follow administration guidelines carefully.

Adrenergic Agents: Nursing Implications 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 and equipment care.

Adrenergic Agents: Nursing Implications Overuse of nasal decongestants may cause rebound nasal congestion or ulcerations. Monitor for therapeutic effects (cardiovascular uses): Decreased edema Increased urinary output Return to normal vital signs Improved skin color and temperature Increased LOC

Adrenergic Agents: Nursing Implications Monitor for therapeutic effects (asthma): Return to normal respiratory rate Improved breath sounds, fewer rales Increased air exchange Decreased cough Less dyspnea Improved blood gases Increased activity tolerance

Adrenergic-Blocking Agents Bind to adrenergic receptors, but inhibit or block stimulation of the sympathetic nervous system (SNS) Have the opposite effect of adrenergic agents Also known as adrenergic antagonists or sympatholytics

Adrenergic-Blocking Agents: Drug Effects and Therapeutic Uses Alpha-Blockers Cause both arterial and venous dilation, reducing peripheral vascular resistance and BP Used to treat hypertension Effect on receptors on prostate gland and bladder decreased resistance to urinary outflow, thus reducing urinary obstruction and relieving effects of BPH

Beta Blockers: Mechanism of Action Cardioselective (Beta1) Decreases heart rate Prolongs SA node recovery Slows conduction rate through the AV node Decreases myocardial contractility, thus decreasing myocardial oxygen demand

Beta Blockers: Therapeutic Uses Anti-angina:decreases demand for myocardial oxygen Cardioprotective:inhibits stimulation by circulating catecholamines Class II antidysrhythmic Antihypertensive Treatment of migraine headaches Glaucoma (topical use)

Adrenergic Blocking Agents: Nursing Implications Assess for allergies and history of COPD, hypotension, cardiac dysrhythmias, bradycardia, CHF, or other cardiovascular problems Remember that alpha blockers may precipitate hypotension. Remember that beta blockers may precipitate bradycardia, hypotension, heart block, CHF, and bronchoconstriction.

Encourage patients to take medications as prescribed. These medications should never be stopped abruptly. Report constipation or the development of any urinary or bladder distention. Rebound hypertension or chest pain may occur if this medication is discontinued abruptly. Patients should notify their physician if they become ill and unable to take medication. Inform patients that they may notice a decrease in their tolerance for exercise; dizziness and fainting may occur with increased activity. Notify the physician if these problems occur.

Beta Blocking Agents: Nursing Implications Patients should report the following to their physician: Weight gain of more than 2 pounds (1 kg) within a week Edema of the feet or ankles Shortness of breath Excessive fatigue or weakness Syncope or dizziness

Monitor for side effects, including: Hypotension Fatigue Tachycardia (alpha blockers) Lethargy Bradycardia Depression Heart block Insomnia CHF nightmares Increased airway resistance

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