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Adrenergic blockers



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  • 1. Drugs Affecting The Autonomic Nervous System Adrenergic Agents and Adrenergic-Blocking Agents
  • 2. Adrenergic Agents
    • Drugs that stimulate the sympathetic nervous system (SNS)
  • 3. Adrenergic Agents
    • Also known as
    • adrenergic agonists or sympathomimetics
  • 4. Adrenergic Agents
    • Mimic the effects of the SNS neurotransmitters:
    • norepinephrine (NE) and epinephrine (EPI)
  • 5. Adrenergic Receptors
    • Located throughout the body
    • Are receptors for the sympathetic neurotransmitters
    • Alpha-adrenergic receptors: respond to NE
    • Beta-adrenergic receptors: respond to EPI
  • 6. Alpha-Adrenergic Receptors
    • Divided into alpha1 and alpha 2 receptors
    • Differentiated by their location on nerves
  • 7. Alpha 1 -Adrenergic Receptors
    • Located on postsynaptic effector cells (the cell, muscle, or organ that the nerve stimulates)
  • 8. Alpha 2 -Adrenergic Receptors
    • Located on presynaptic nerve terminals (the nerve that stimulates the effector cells)
    • Control the release of neurotransmitters
  • 9. The predominant alpha-adrenergic agonist responses are:
    • Vasoconstriction and CNS stimulation
  • 10. Beta-Adrenergic Receptors
    • All are located on postsynaptic effector cells
    • Beta 1 -adrenergic receptors—located primarily in the heart
    • Beta 2 -adrenergic receptors—located in smooth muscle of the bronchioles, arterioles, and visceral organs
  • 11. The beta-adrenergic agonist response results in:
    • Bronchial, GI, and uterine smooth muscle relaxation
    • Glycogenolysis
    • Cardiac stimulation
  • 12. 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
  • 13. Adrenergic Receptor Responses to Stimulation
    • Blood vessels alpha 1 and beta 2 Constriction / dilation
    • Cardiac muscle beta 1 Increased contractility
    • AV Node beta 1 Increased heart rate
    • SA Node beta 1 Increased heart rate
  • 14. Adrenergic Receptor Responses to Stimulation
    • Muscle beta 2 Decreased motility
    • Sphincters alpha 1 Constriction
  • 15. Adrenergic Receptor Responses to Stimulation
    • Bladder alpha 1 Constriction sphincter
    • Penis alpha 1 Ejaculation
    • Uterus alpha 1 and beta 2 Contraction/ relaxation
  • 16. Adrenergic Receptor Responses to Stimulation
    • Bronchial beta 2 Dilation/relaxation muscles
  • 17. Catecholamines
    • Substances that can produce a sympathomimetic response
    • Endogenous:
    • epinephrine, norepinephrine,dopamine
    • Synthetic:
    • isoproterenol, dobutamine, phenylephrine
  • 18. Adrenergic Agents Mechanism of Action
    • Direct-acting sympathomimetic:
    • Binds directly to the receptor and causes a physiologic response
  • 19. Adrenergic Agents Mechanism of Action
    • 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
  • 20. Adrenergic Agents Mechanism of Action
    • 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
  • 21. 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)
  • 22. Drug Effects of Adrenergic Agents
    • Stimulation of beta 2 -adrenergic receptors on the airways results in:
    • Bronchodilation (relaxation of the bronchi)
    • Uterine relaxation
    • Glycogenolysis in the liver
  • 23. 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)
  • 24. Adrenergic Agents: Therapeutic Uses
    • Anorexiants: adjuncts to diet in the short-term management of obesity
    • Examples: benzphetamine phentermine dextroamphetamine Dexedrine
  • 25. Adrenergic Agents: Therapeutic Uses
    • Bronchodilators: treatment of asthma and bronchitis
    • Agents that stimulate beta 2 -adrenergic receptors of bronchial smooth muscles causing relaxation
    • Examples:
    • albuterol ephedrine epinephrine isoetharine isoproterenol levalbuterol metaproterenol salmeterol terbutaline
    • These agents may also affect uterine and vascular smooth muscles.
  • 26. Adrenergic Agents: Therapeutic Uses
    • Reduction of intraocular pressure and mydriasis (pupil dilation): treatment of open-angle glaucoma
    • Examples: epinephrine and dipivefrin
  • 27. Adrenergic Agents: Therapeutic Uses
    • 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
  • 28. Adrenergic Agents: Therapeutic Uses
    • Ophthalmic
    • Topical application to the eye surface affects the vasculature of the eye, stimulating alpha receptors on small arterioles, thus relieving conjunctival congestion.
    • Examples: epinephrine naphazoline phenylephrine tetrahydrozoline
  • 29. Adrenergic Agents: Therapeutic Uses
    • Vasoactive sympathomimetics (pressors, inotropes), also called cardioselective sympathomimetics
    • Used to support the heart during cardiac failure or shock.
    • Examples:
    • dobutamine dopamine ephedrine epinephrine fenoldopam isoproterenol methoxamine norepinephrine phenylephrine
  • 30. 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)
  • 31. 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
  • 32. Adrenergic Agents: Interactions
    • Anesthetic agents
    • Tricyclic antidepressants
    • MAOIs
    • Antihistamines
    • Thyroid preparations
    • Antihypertensives
    • Will directly antagonize another adrenergic agent, resulting in reduced effects
  • 33. 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.
  • 34. Adrenergic Agents: Nursing Implications
    • IV administration:
    • Check IV site often for infiltration
    • Use clear IV solutions
    • Use an infusion device/IV pump
    • Infuse agent slowly to avoid dangerous cardiovascular effects
    • Monitor cardiac rhythm
  • 35. 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.
    • Salmeterol is indicated for PREVENTION of bronchospasms, not management of acute symptoms.
  • 36. Adrenergic Agents: Nursing Implications
    • Overuse of nasal decongestants may cause rebound nasal congestion or ulcerations.
    • Avoid OTC or other medications because of possible interactions.
    • Administering two adrenergic agents together may precipitate severe cardiovascular effects such as tachycardia or hypertension.
    • Inform patients taking inhaled isoproterenol that their sputum or saliva may turn pink.
  • 37. Adrenergic Agents: Nursing Implications
    • Monitor for therapeutic effects (cardiovascular uses):
    • Decreased edema
    • Increased urinary output
    • Return to normal vital signs
    • Improved skin color and temperature
    • Increased LOC
  • 38. 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
  • 39. Adrenergic-Blocking Agents
    • Bind to adrenergic receptors, but inhibit or block stimulation of the sympathetic nervous system (SNS)
  • 40. Adrenergic Blocking Agents
    • Have the opposite effect of adrenergic agents
    • Also known as
      • adrenergic antagonists or sympatholytics
  • 41. Adrenergic Blocking Agents
    • Sympatholytics inhibit—or LYSE—sympathetic neurotransmitters (norepinephrine and epinephrine)
  • 42. Adrenergic Blocking Agents
    • Classified by the type of adrenergic receptor they block
    • Alpha 1 and alpha 2 receptors
    • Beta 1 and beta 2 receptors
  • 43. Adrenergic-Blocking Agents: Drug Effects and Therapeutic Uses
    • Ergot Alkaloids (Alpha-Blockers)
    • Constrict dilated arteries going to the brain (carotid arteries)
    • Used to treat vascular headaches (migraines)
    • Stimulate uterine contractions by inducing vasoconstriction
    • Used to control postpartum bleeding
  • 44. 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
  • 45. Adrenergic-Blocking Agents: Drug Effects and Therapeutic Uses
    • Alpha-Blockers
    • Phentolamine
      • Quickly reverses the potent vasoconstrictive effects of extravasated vasopressors such as norepinephrine or epinephrine.
      • Restores blood flow and prevents tissue necrosis.
  • 46. Adrenergic-Blocking Agents: Side Effects
    • Alpha Blockers
    • Body System Side/Adverse Effects
    • Cardiovascular Palpitations, orthostatic hypotension, tachycardia, edema, dysrhythmias, chest pain
    • CNS Dizziness, headache, drowsiness, anxiety, depression, vertigo, weakness, numbness, fatigue
  • 47. Adrenergic-Blocking Agents: Side Effects
    • Alpha Blockers
    • Body System Side/Adverse Effects
    • Gastrointestinal Nausea, vomiting, diarrhea, constipation, abdominal pain
    • Other Incontinence, nose bleeding, tinnitus, dry mouth, pharyngitis, rhinitis
  • 48. Beta Blockers
    • Block stimulation of beta receptors in the SNS
    • Compete with norepinephrine and epinephrine
    • Selective and nonselective beta blockers
  • 49. Beta Receptors
    • Beta 1 Receptors
    • Located primarily on the heart
    • Beta blockers selective for these receptors are called cardioselective beta blockers
  • 50. Beta Receptors
    • Beta 2 Receptors
    • Located primarily on smooth muscles of bronchioles and blood vessels
  • 51. Nonspecific Beta Blockers
    • Beta blockers that block both beta 1 and beta 2 receptors
  • 52. 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
  • 53. Beta Blockers: Mechanism of Action
    • Nonspecific (Beta 1 and Beta 2 )
    • Effects on heart: Same as cardioselective
    • Bronchioles: Constriction, resulting in narrowing of airways and shortness of breath
    • Blood vessels: Vasoconstriction
  • 54. Beta Blockers: Therapeutic Uses
    • Anti-angina: decreases demand for myocardial oxygen
    • Cardioprotective: inhibits stimulation by circulating catecholamines
    • Class II antidysrhythmic
  • 55. Beta Blockers: Therapeutic Uses
    • Antihypertensive
    • Treatment of migraine headaches
    • Glaucoma (topical use)
  • 56. Beta Blockers: Side Effects
    • Body System Side/Adverse Effects
    • Blood Agranulocytosis, thrombocytopenia
    • Cardiovascular AV block, bradycardia, congestive heart failure, peripheral vascular insufficiency
    • CNS Dizziness, mental depression, lethargy, hallucinations
  • 57. Adrenergic-Blocking Agents: Side Effects
    • Beta Blockers
    • Body System Side/Adverse Effects
    • Gastrointestinal Nausea, dry mouth, vomiting, diarrhea, cramps, ischemic colitis
    • Other Impotence, rash, alopecia, bronchospasms
  • 58. Adrenergic Blocking Agents: Nursing Implications
    • Assess for allergies and history of COPD, hypotension, cardiac dysrhythmias, bradycardia, CHF, or other cardiovascular problems
      • Any preexisting condition that might be exacerbated by the use of these agents might be a CONTRAINDICATION to their use.
  • 59. Adrenergic Blocking Agents: Nursing Implications
    • Remember that alpha blockers may precipitate hypotension.
    • Remember that beta blockers may precipitate bradycardia, hypotension, heart block, CHF, and bronchoconstriction.
  • 60. Adrenergic Blocking Agents: Nursing Implications
    • Avoid OTC medications because of possible interactions.
    • Possible drug interactions may occur with:
      • Antacids (aluminum hydroxide type)
      • Antimuscarinics/anticholinergics
      • Diuretics and cardiovascular drugs
      • Neuromuscular blocking agents
      • Oral hypoglycemic agents
  • 61. Adrenergic Blocking Agents: Nursing Implications
    • Encourage patients to take medications as prescribed.
    • These medications should never be stopped abruptly.
    • Report constipation or the development of any urinary hesitancy or bladder distention.
  • 62. Adrenergic Blocking Agents: Nursing Implications
    • Teach patients to change positions slowly to prevent or minimize postural hypotension.
    • Avoid caffeine (excessive irritability).
    • Avoid alcohol ingestion and hazardous activities until blood levels become stable.
    • Patients should notify their physician if palpitations, dyspnea, nausea, or vomiting occur.
  • 63. Beta Blocking Agents: Nursing Implications
    • 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.
  • 64. 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
  • 65. Adrenergic Blocking Agents: Nursing Implications
    • Monitor for side effects, including:
    • Hypotension Fatigue
    • Tachycardia (alpha blockers) Lethargy
    • Bradycardia Depression
    • Heart block Insomnia
    • CHF Vivid nightmares
    • Increased airway resistance
  • 66. Adrenergic Blocking Agents: Nursing Implications
    • Monitor for therapeutic effects
    • Decreased chest pain in patients with angina
    • Return to normal BP and P
    • Other specific effects, depending on the use
  • 67. Alpha-Adrenergic Blockers
    • Type of blockade Phenoxybenzamine – non-competitive; slow onset and long duration. 2-stage blockade. All the rest: competitive
    • Selectivity Nonselective: Phenoxybenzamine and phentolamine alpha-1 selective: Prazosin, terazosin, others alpha-2 selective: Yohimbine alpha/beta blockers: Labetalol
    • Others: phenothiazines, tricyclic antidepressants
  • 68. Phenoxybenzamine Prazosin Yohimbine www.freelivedoctor.com
  • 69. EPI EPI + Phenoxybenzamine Phenoxybenzamine alone Receptors no longer available [Agonist], mg/kg % Maximal Increase Decrease in the maximal efficacy of Epi due to a decrease in the number of receptors www.freelivedoctor.com
  • 70. Pharmacological Effects -Phenoxybenxamine
    • Cardiovascular system Blood pressure Cardiac Effects Organ Blood Flow Capillaries
    • Central nervous system
    • Respiratory system
  • 71. Pharmacological Effects – cont’d
    • Eye - miosis
    • GI tract – Increased motility
    • Urinary bladder – decreased tone in sphincter
    • Metabolic effects – increased insulin secretion
  • 72. Adverse effects
    • Postural hypotension
    • Tachycardia
    • Sedation
    • Nasal stuffiness
    • Miosis
    • Impotence (inhibits ejaculation)
    • Exercise care in hypovolemic patients
  • 73. Imidazoline derivatives - phentolamine
    • Many other effects including:
    • Parasympathomimetic
    • Increased gastric acid secretion
    • Cardiac stimulation
    • Increased secretion from exocrine glands, such as salivary, sweat, lacrimal, pancreatic
    • Coronary artery disease and peptic ulcer relative contraindication to it.
  • 74. Alpha-1 selective blockers Prazosin
    • Less cardiac stimulation since it preserves alpha-2 mediated negative feedback + other mechanisms
    • Used in congestive heart failure and in hypertension but tolerance develops with time, maybe due to fluid retention.
    • Adverse effects: First dose phenomenon.
    • Favorable effect on plasma lipids: increase HDL/LDL ratio
  • 75. ADR (µg/Kg) 1 10 100 500 0.1 1 10 100 500 +PRAZOSIN BP HR Effect of Adrenaline (ADR) on Blood Pressure and Heart Rate Before and After Prazosin www.freelivedoctor.com
  • 76. Alpha-2 selective blockers Yohimbine
    • Cardiovascular effects – peripheral and central effects
    • Blocks other receptors also – serotonin, dopamine
    • Increases ADH release
    • Enhances sexual activity – aphrodisiac
    • Potential uses: depression, obesity, NIDDM
  • 77. Ergot alkaloids
    • Interact with serotonin and dopamine receptors also
    • Direct smooth muscle contraction
    • Structure-activity relationships
    • Coronary vasoconstriction
    • Toxicity: GI, vascular insufficiency –ergotism
    • Use in migraine and post-partum
  • 78. Therapeutic Uses of Alpha-Adrenergic Blockers
    • Hypertension - alpha-1 selective
    • Conditions associated with increased sympathetic activity – e.g. pheochromocytoma
    • Hemodynamic shock
    • Peripheral vascular disease – Raynaud’s
    • Congestive heart failure
    • Benign prostatic hyperplasia
    • Pulmonary hypertension – tolazoline
    • Yohimbine or intracavernous phentolamine+papaverine for impotence