Download Sympathomimetics

Autonomic Nervous System
I. ANS controls involuntary processes
A. Composed of :
1. Sympathetic (adrenergic) nervous system
2. Parasympathetic (cholinergic) nervous system.
B. SNS & PNS together maintain a balance—Work as a team
II. Sympathetic Nervous System
A. “Fight or flight” or “Speedy”
B. Adrenergic receptors:
1. Alpha-adrenergic Receptor
a) Alpha 1
b) Alpha 2
2. Beta- adrenergic receptors
a) Beta 1
b) Beta 2
3. Dopaminergic Receptors
a) Causes vessels of the renal, mesenteric, coronary and cerebral arteries to
dilate.
b) Only DOPAmine will stimulate these receptors.
III.
Neurotransmitters are chemicals used to carry impulses from neurons to neurons or
from neurons to tissue receptors.
A. Catecholamines: SNS neurotransmitters
1. Norepinephrine
2. Epinephrine
3. Dopamine
B. Norepinephrine is the primary neurotransmitter for SNS.
C. Catecholamines are metabolized by two enzymes in the synaptic cleft and the liver
1. Monoamine oxidase (MAO)
2. Catechol-o-methyltransferase (COMT)
3. Their job is to metabolize or biotransform any remaining norepinephrine after
adrenergic transmission.
D. SNS response
1. Catecholamines produced by SNS
2. Stored in vesicles or granules in the ends of nerves and waits for the nerve to be
stimulated
3. Stimulation causes release of catecholamine into the synaptic cleft (space between
nerve ending and effector organ)
4. Catecholamines bind to receptor sites
5. Effector organ responds
6. This action is stopped by action of action of enzymes and reuptake of the
neurotransmitter
IV. ANS Terminology
A. Sympathomimetic = Sympathetic Agonist = Adrenergic Agonist
B. Sympatholytic = Sympathetic Antagonist = Adrenergic Antagonist
C. Neurotransmitters = Catecholamines
Sympathetic Nervous System Receptors/Response
Receptor
1
2
1
2
Location
1. Smooth muscles of peripheral
blood vessels
2. Sphincters of GI & GU tracts/
3. Bladder Sphincter
4. Penis
5. Iris
1. Nerve membranes
1. One heart- receptors in heart
muscles
2. Beta cells of Pancreas
3. Kidney
1. Two lobes of lungs-receptors in
bronchial muscles
2. Uterus smooth muscles
3. Liver
4. Skeletal muscles
5. Blood Vessels (Brain, heart and
skeletal vessels)
Stimulation
1. vasoconstriction
2.  GI motility
3. Constriction
4. Ejaculation
5. Mydriasis -dilates pupil
6.  Secretions
7. Stress induced sweating
1.  CNS sympathetic outflow
1. Heart rate
 Contractility
2. Decreased Insulin
3. Increased renin secretion
1. Bronchodilation
2.
3.
4.
5.
V. Therapeutic uses of adrenergic:
A. Anorexiants
1. dextroamphetamine sulfate (Dexedrine)
B. ADHD
1. methylphenidate hydrochloride (Ritalin)
C. Bronchodilation
1. albuterol sulfate (Proventil, Ventolin)
2. epinephrine (Adrenalin)
3. isoproterenol hydrochloride (Isuprel)
4. terbutaline (Brethine)
5. salmeterol (Serevent)
D. Reduce intraocular pressure & mydriasis
1. epinephrine
2. dipivefrin
E. Nasal decongestants
1. pseudoephedrine hydrochloride (Sudafed, Afrin)
F. Ophthalmics
1. Tetrahydrozoline (Murine, Visine)
2. naphazoline (Allerest)
Relaxation
Glycogenolysis
Tremors
Dilation
3. See textbook chapter “Ophthalmic Agents” for more information:  IOP by 
production of aqueous humor and  outflow
G. Vasoactive sympathomimetics: (AKA: vasopressors or “pressors”)
1. DOBUTamine (Dobutrex)
a) Beta 1 selective
b) Similar to dopamine
c) Increases cardiac output/ +inotrope
d) IV injection
e) Dosage 2.5-10 mcg/kg/min
f) CHF
2. DOPAmine (Intropin)
a) Dopaminergic, beta1, and alpha1 receptor activity
b) Drug of choice for treatment of shock and hypotensive states because it
causes an increase in renal blood flow and does not cause renal shut down.
c) IV: Dosage 2-5 mcg/kg/min; up to 50 mcg/kg/min
Dopamine’s Dose Related Response
Dose
Low dose
Receptors Affected
Dopamine
Medium dose
Beta one receptors
High dose
Alpha one receptors
Response
 blood flow to mesentery, brain, and heart
Dilates renal arteries
 renal perfusion
 urinary output
 Contractility
 HR
 Cardiac output
 B/P (vasoconstriction)
3. Epinephrine (Adrenalin, EpiPen, Primatene)
a) Prototype of adrenergic drugs
b) Routes: orally, SC, IM, IV
c) At Low Doses stimulates beta receptors
i. Ananaphylactic shock-rapid onset of action, SQ  5- 10 minutes,
prevents the release of histamine
ii. Bronchospasms-Asthma
iii. Cardiac Arrest-restores rhythm
iv. Ophthalmic-glaucoma
d) At Large Doses stimulates alpha receptors
i. Cardiac Arrest—increases B/P through vasoconstriction and also increases
blood flow to skeletal muscles, heart and brain.
ii. Local Anesthetics- prolongs actions, prevents systemic absorption and
minimizes bleeding.
1. Don’t use in local anesthesia (Lidocaine with Epi) in toes or fingers as
it can decrease distal circulation.
2. Epinephrine is used in some preparations of lidocaine?
Don’t confuse Epinephrine 1:100 with Epinephrine 1:1000 as OD has caused
fatalities. Always check the strength!!
Epinephrine %
1%
0.5%
0.1%
0.01%
0.001%
Concentration
1:100
1:200
1:1,000
1:10,000
1:100,000
Route
Inhalation
SQ
SQ/IM
IV
Intradermal
4. Isoproterenol (Isuprel)
a) Beta receptor selective
b) Cardiac stimulant, bronchodilator
c) Closely monitor heart rate and rhythm
5. Midodrine (ProAmatine)
6. Norepinephrine (Levophed)
a) Alpha and beta activity
b) Causes vasoconstriction used to tx hypotension & shock
c) Avoid extravasation
d) Phentolamine (Regitine): antidote; this drug is an alpha-adrenergic blocker
that can be used for extravasation of Levophed or Dopamine
7. Phenylephrine (Neo-Synephrine)
a) Alpha1 receptors
b) Short term treatment of shock
c) Control dysrhythmias
d) Nasal decongestant
e) Ophthalmic agent (mydriasis-eye exams)
f) Used with regional anesthesia to produce vasoconstriction
8. Phenylpropanolamine
a) OTC products containing this pulled by FDA because of SEs
VI. Side Effects of Adrenergics:
 Palpitations
 Nervousness, restlessness
 Sweating
 H/A
 Difficulty urinating
 Pale, cold skin
 Tachycardia
 Dyspnea
 B/P liability
 N/V

VII. Nursing Considerations for Sympathomimetic Vasopressors
A. Continuously monitor cardiac function
B. Monitor EKG, BP, HR, I & O
C. Labs: K+ level