Drugs%20Affecting%20Autonomic%20Nervous%20System%201

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Drugs Affecting Autonomic Nervous System 1
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Lecture objectives

• Identify the anatomy of nervous system.
• Identify the drugs that effect ANS

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Nervous System Divisions
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Nervous System Overview

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

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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

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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

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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

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Catecholamines

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

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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

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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

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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)

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Adrenergic Receptors

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

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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.

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?-receptor types

• ?-adrenergic receptors respond particularly to
  epinephrine and to such blocking agents as
  propranolol.
• There are three known types of beta receptor,
  designated ß1, ß2 and ß3.
• ß1-Adrenergic receptors are located mainly in the
  heart.
• ß2-Adrenergic receptors are located mainly in the
  lungs, gastrointestinal tract, liver, uterus,
  vascular smooth muscle, and skeletal muscle.
• ß3-receptors are located in fat cells.

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What do the receptors do?Activation of ?
receptors leads to smooth muscle
contractionActivation of ?2 receptors leads to
smooth muscle relaxationActivation of ?1
receptors leads to smooth muscle contraction
(especially in heart)
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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)
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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)

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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

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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

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Adrenergic Agents Therapeutic Uses

• Anorexiants adjuncts to diet in the short-term
  management of obesity
• Examples benzaphetamine phentermine dextroam
  phetamine Dexedrine
• 2.Bronchodilators treatment of asthma and
  bronchitis
• Agents that stimulate beta2-adrenergic receptors
  of bronchial smooth muscles causing relaxation
• Examples
• albuterol ephedrine epinephrineisoetharine
  isoproterenol levalbuterolmetaproterenol salmete
  rol terbutaline

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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.
• Examplesepinephrine ephedrine naphazoline
  phenylephrine tetrahydrozoline

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• 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 fenoldo
  pam isoproterenol methoxamine norepinephrine pheny
  lephrine

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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)

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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

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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.

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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.

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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

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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

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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

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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

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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

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Beta Blockers Therapeutic Uses

1. Anti-anginadecreases demand for myocardial
   oxygen
2. Cardioprotectiveinhibits stimulation by
   circulating catecholamines
3. Class II antidysrhythmic
4. Antihypertensive
5. Treatment of migraine headaches
6. Glaucoma (topical use)

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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.

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• 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.

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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

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Monitor for side effects, including

1. Hypotension
2. Fatigue
3. Tachycardia (alpha blockers)
4. Lethargy
5. Bradycardia
6. Depression
7. Heart block
8. Insomnia
9. CHF
10. nightmares
11. Increased airway resistance

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• QUESTION?