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Adrenergic blockers
 

Adrenergic blockers

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    Adrenergic blockers Adrenergic blockers Presentation Transcript

    • Drugs Affecting The Autonomic Nervous System Adrenergic Agents and Adrenergic-Blocking Agents
    • Adrenergic Agents
      • Drugs that stimulate the sympathetic nervous system (SNS)
    • Adrenergic Agents
      • Also known as
      • adrenergic agonists or sympathomimetics
    • Adrenergic Agents
      • 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
    • Alpha-Adrenergic Receptors
      • Divided into alpha1 and alpha 2 receptors
      • Differentiated by their location on nerves
    • Alpha 1 -Adrenergic Receptors
      • Located on postsynaptic effector cells (the cell, muscle, or organ that the nerve stimulates)
    • Alpha 2 -Adrenergic Receptors
      • Located on presynaptic nerve terminals (the nerve that stimulates the effector cells)
      • Control the release of neurotransmitters
    • The predominant alpha-adrenergic agonist responses are:
      • Vasoconstriction and CNS stimulation
    • 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
    • The beta-adrenergic agonist response results in:
      • Bronchial, GI, and uterine smooth muscle relaxation
      • Glycogenolysis
      • Cardiac stimulation
    • 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 Receptor Responses to Stimulation
      • LOCATION RECEPTOR RESPONSE Cardiovascular
      • 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
    • Adrenergic Receptor Responses to Stimulation
      • LOCATION RECEPTOR RESPONSE Gastrointestinal
      • Muscle beta 2 Decreased motility
      • Sphincters alpha 1 Constriction
    • Adrenergic Receptor Responses to Stimulation
      • LOCATION RECEPTOR RESPONSE Genitourinary
      • Bladder alpha 1 Constriction sphincter
      • Penis alpha 1 Ejaculation
      • Uterus alpha 1 and beta 2 Contraction/ relaxation
    • Adrenergic Receptor Responses to Stimulation
      • LOCATION RECEPTOR RESPONSE Respiratory
      • Bronchial beta 2 Dilation/relaxation muscles
    • Catecholamines
      • Substances that can produce a sympathomimetic response
      • Endogenous:
      • epinephrine, norepinephrine,dopamine
      • Synthetic:
      • isoproterenol, dobutamine, phenylephrine
    • Adrenergic Agents Mechanism of Action
      • Direct-acting sympathomimetic:
      • Binds directly to the receptor and causes a physiologic response
    • 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
    • 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
    • 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 beta 2 -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)
    • Adrenergic Agents: Therapeutic Uses
      • Anorexiants: adjuncts to diet in the short-term management of obesity
      • Examples: benzphetamine phentermine dextroamphetamine Dexedrine
    • 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.
    • Adrenergic Agents: Therapeutic Uses
      • Reduction of intraocular pressure and mydriasis (pupil dilation): treatment of open-angle glaucoma
      • Examples: epinephrine and dipivefrin
    • 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
    • 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
    • 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
    • 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: Interactions
      • Anesthetic agents
      • Tricyclic antidepressants
      • MAOIs
      • Antihistamines
      • Thyroid preparations
      • Antihypertensives
      • Will directly antagonize another adrenergic agent, resulting in reduced effects
    • 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
      • 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
    • 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.
    • 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.
    • 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
    • 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)
    • Adrenergic Blocking Agents
      • Have the opposite effect of adrenergic agents
      • Also known as
        • adrenergic antagonists or sympatholytics
    • Adrenergic Blocking Agents
      • Sympatholytics inhibit—or LYSE—sympathetic neurotransmitters (norepinephrine and epinephrine)
    • Adrenergic Blocking Agents
      • Classified by the type of adrenergic receptor they block
      • Alpha 1 and alpha 2 receptors
      • Beta 1 and beta 2 receptors
    • 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
    • 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
    • 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.
    • 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
    • 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
    • Beta Blockers
      • Block stimulation of beta receptors in the SNS
      • Compete with norepinephrine and epinephrine
      • Selective and nonselective beta blockers
    • Beta Receptors
      • Beta 1 Receptors
      • Located primarily on the heart
      • Beta blockers selective for these receptors are called cardioselective beta blockers
    • Beta Receptors
      • Beta 2 Receptors
      • Located primarily on smooth muscles of bronchioles and blood vessels
    • Nonspecific Beta Blockers
      • Beta blockers that block both beta 1 and beta 2 receptors
    • 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: 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
    • Beta Blockers: Therapeutic Uses
      • Anti-angina: decreases demand for myocardial oxygen
      • Cardioprotective: inhibits stimulation by circulating catecholamines
      • Class II antidysrhythmic
    • Beta Blockers: Therapeutic Uses
      • Antihypertensive
      • Treatment of migraine headaches
      • Glaucoma (topical use)
    • 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
    • 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
    • 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.
    • 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.
    • 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
    • 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.
    • 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.
    • 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.
    • 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
    • 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
    • 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
    • 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
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    • Phenoxybenzamine Prazosin Yohimbine www.freelivedoctor.com
    • 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
    • Pharmacological Effects -Phenoxybenxamine
      • Cardiovascular system Blood pressure Cardiac Effects Organ Blood Flow Capillaries
      • Central nervous system
      • Respiratory system
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    • Pharmacological Effects – cont’d
      • Eye - miosis
      • GI tract – Increased motility
      • Urinary bladder – decreased tone in sphincter
      • Metabolic effects – increased insulin secretion
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    • Adverse effects
      • Postural hypotension
      • Tachycardia
      • Sedation
      • Nasal stuffiness
      • Miosis
      • Impotence (inhibits ejaculation)
      • Exercise care in hypovolemic patients
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    • 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.
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    • 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
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    • 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
    • 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
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    • 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
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    • 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
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