Drugs Affecting
The
Autonomic Nervous System
ADRENERGIC AGENTS and ADRENERGIC-BLOCKING AGENTS
Adrenergic agents
- Drugs that stimulate the sympathetic nervous system (SNS)
- also known as adrenergic agonists or symphatomimetic
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
•Are receptors for the sympathetic neurotransmitters
*Alpha-adrenergic receptors: respond to NE Beta-adrenergic receptors: respond to EPI
Dopaminergic Receptors
Adrenergic Receptor Responses to Stimulation: LOCATION RECEPTOR RESPONSE Cardiovascular Blood vessels alpha1 and beta2 Constriction / dilation Cardiac muscle beta1 Increased contractility AV Node beta1 Increased heart rate SA Node beta1 Increased heart rate Gastrointestinal Muscle beta2 Decreased motility Sphincters alpha1 Contractility Genitourinary Bladder alpha1 Constriction sphincter Penis alpha1 Ejaculation Uterus alpha1 & beta Contraction/ relaxation Respiratory Bronchial beta2 Dilation/relaxation of muscles |
Beta-Adrenergic Receptors
All are located on postsynaptic effector cells •Beta1-adrenergic receptors—located primarily in the heart •Beta2-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 Alpha-Adrenergic Receptors •Divided into alpha1 and alpha2 receptors •Differentiated by their location on nerves Alpha1-Adrenergic Receptors •Located on postsynaptic effector cells (the cell, muscle, or organ that the nerve stimulates) Alpha2-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 |
Catecholamines
Substances that can produce a sympathomimetic response:
Endogenous:
•epinephrine, norepinephrine,dopamine
Synthetic:
isoproterenol, dobutamine, phenylephrine
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
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
Mixed-acting sympathomimetic:
•Directly stimulates the receptor by binding to it
•Indirectly stimulates the receptor by causing the release of stored neurotransmitters from the vesicles in the nerve endings
•Binds directly to the receptor and causes a physiologic response
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
Mixed-acting sympathomimetic:
•Directly stimulates the receptor by binding to it
•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)
Stimulation of beta2-adrenergic receptors on the airways results in:
•Bronchodilation (relaxation of the bronchi)
•Uterine relaxation
•Glycogenolysis in the liver
Stimulation of :
•Increased heart rate (positive chronotropic effect)
•Increased conduction through the AV node (positive dromotropic effect)
•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)
Stimulation of beta2-adrenergic receptors on the airways results in:
•Bronchodilation (relaxation of the bronchi)
•Uterine relaxation
•Glycogenolysis in the liver
Stimulation of :
- beta1-adrenergic receptors on the myocardium
- AV node and
- SA node results in CARDIAC STIMULATION:
•Increased heart rate (positive chronotropic effect)
•Increased conduction through the AV node (positive dromotropic effect)
Therapeutic Uses
•Anorexiants: adjuncts to diet in the short-term management of obesity
Examples: benzphetamine
phentermine
dextroamphetamine
Dexedrine
•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
*These agents may also affect uterine and vascular smooth muscles.
•Reduction of intraocular pressure and mydriasis (pupil dilation): treatment of open-angle glaucoma
Examples: epinephrine
dipivefrin
• 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
•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
• Vasoactive sympathomimetics (pressors, inotropes), also called cardioselective sympathomimetic
-Used to support the heart during cardiac failure or shock.
Examples: dobutamine dopamine ephedrine
epinephrine fenoldopam isoproterenol
methoxamine norepinephrine phenylephrine
Examples: benzphetamine
phentermine
dextroamphetamine
Dexedrine
•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
*These agents may also affect uterine and vascular smooth muscles.
•Reduction of intraocular pressure and mydriasis (pupil dilation): treatment of open-angle glaucoma
Examples: epinephrine
dipivefrin
• 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
•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
• Vasoactive sympathomimetics (pressors, inotropes), also called cardioselective sympathomimetic
-Used to support the heart during cardiac failure or shock.
Examples: dobutamine dopamine ephedrine
epinephrine fenoldopam isoproterenol
methoxamine norepinephrine phenylephrine
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)
Beta-Adrenergic Effects
•CNS:–mild tremors, headache, nervousness, dizziness
•Cardiovascular:–increased heart rate, palpitations (dysrhythmias), fluctuations in BP
•Other:-sweating, nausea, vomiting, muscle cramps
•CNS: –headache, restlessness, excitement, insomnia, euphoria
•Cardiovascular: –palpitations (dysrhythmias), tachycardia, vasoconstriction, hypertension
•Other: anorexia, dry mouth, nausea, vomiting, taste changes (rare)
Beta-Adrenergic Effects
•CNS:–mild tremors, headache, nervousness, dizziness
•Cardiovascular:–increased heart rate, palpitations (dysrhythmias), fluctuations in BP
•Other:-sweating, nausea, vomiting, muscle cramps
Interactions
•Anesthetic agents
•Tricyclic antidepressants
•MAOIs
•Antihistamines
•Thyroid preparations
•Antihypertensives
•Will directly antagonize another adrenergic agent, resulting in reduced effects
•Tricyclic antidepressants
•MAOIs
•Antihistamines
•Thyroid preparations
•Antihypertensives
•Will directly antagonize another adrenergic agent, resulting in reduced effects
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.
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
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.
•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.
Monitor for therapeutic effects (cardiovascular uses):
•Decreased edema
•Increased urinary output •Return to normal vital signs
•Improved skin color and temperature
•Increased LOC
•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
•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.
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
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.
•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.
Monitor for therapeutic effects (cardiovascular uses):
•Decreased edema
•Increased urinary output •Return to normal vital signs
•Improved skin color and temperature
•Increased LOC
•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
•Sympatholytics inhibit—or LYSE—sympathetic neurotransmitters (norepinephrine and epinephrine)
Classified by the type of adrenergic receptor they block:
•Alpha1 and alpha2 receptors
•Beta1 and beta2 receptors
•Have the opposite effect of adrenergic agents
•Also known as –adrenergic antagonists or sympatholytics
•Sympatholytics inhibit—or LYSE—sympathetic neurotransmitters (norepinephrine and epinephrine)
Classified by the type of adrenergic receptor they block:
•Alpha1 and alpha2 receptors
•Beta1 and beta2 receptors
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
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
Alpha-Blockers
•Phentolamine –Quickly reverses the potent vasoconstrictive effects of extravasated vasopressors such as
norepinephrine or epinephrine. –Restores blood flow and prevents tissue necrosis.
•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
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
Alpha-Blockers
•Phentolamine –Quickly reverses the potent vasoconstrictive effects of extravasated vasopressors such as
norepinephrine or epinephrine. –Restores blood flow and prevents tissue necrosis.
Side Effects
Alpha Blockers
Body System Side/Adverse Effects
Cardiovascular Palpitations, orthostatic, edema, dysrhythmias
hypotension, tachycardia, chest pain
CNS Dizziness, headache, drowsiness,
anxiety, depression, vertigo,
weakness, numbness, fatigue
Gastrointestinal Nausea, vomiting, diarrhea,
constipation, abdominal pain
Other Incontinence, nose bleeding,
tinnitus, dry mouth, pharyngitis, rhinitis
Body System Side/Adverse Effects
Cardiovascular Palpitations, orthostatic, edema, dysrhythmias
hypotension, tachycardia, chest pain
CNS Dizziness, headache, drowsiness,
anxiety, depression, vertigo,
weakness, numbness, fatigue
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
Beta1 Receptors
•Located primarily on the heart
•Beta blockers selective for these receptors are called cardioselective beta blockers
Beta2 Receptors
•Located primarily on smooth muscles of bronchioles and blood vessels
•Block stimulation of beta receptors in the SNS
•Compete with norepinephrine and epinephrine
•Selective and nonselective beta blockers
Beta1 Receptors
•Located primarily on the heart
•Beta blockers selective for these receptors are called cardioselective beta blockers
Beta2 Receptors
•Located primarily on smooth muscles of bronchioles and blood vessels
Nonspecific Beta Blockers
•Beta blockers that block both beta1 and beta2 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
Nonspecific (Beta1 and Beta2)
•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
•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
•other cardiovascular problems
*Any preexisting condition that might be exacerbated by the use of these agents might be a CONTRAINDICATION to their use.
•Remember that alpha blockers may precipitate hypotension.
•Remember that beta blockers may precipitate bradycardia, hypotension, heart block, CHF, and bronchoconstriction.
•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
•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.
•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.
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.
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 weaknessSyncope 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
Monitor for therapeutic effects:
•Decreased chest pain in patients with angina
•Return to normal BP and other specific effects, depending on the use
•Decreases heart rate
•Prolongs SA node recovery
•Slows conduction rate through the AV node
•Decreases myocardial contractility, thus decreasing myocardial oxygen demand
Nonspecific (Beta1 and Beta2)
•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
•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
•other cardiovascular problems
*Any preexisting condition that might be exacerbated by the use of these agents might be a CONTRAINDICATION to their use.
•Remember that alpha blockers may precipitate hypotension.
•Remember that beta blockers may precipitate bradycardia, hypotension, heart block, CHF, and bronchoconstriction.
•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
•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.
•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.
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.
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 weaknessSyncope 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
Monitor for therapeutic effects:
•Decreased chest pain in patients with angina
•Return to normal BP and other specific effects, depending on the use