Transcript Autonomic Nervous System

Drugs Affecting the Autonomic
Nervous System
NRSG 305 – Pharmacology in Nursing
by Joanna Shedd, MS, RN
1
Autonomic Nervous System
• Parasympathetic>preganglionic>post
ganglionic>release ach>binds to
cholinergic nerves> Muscarinic
• Sympathetic>preganglionic>post
ganglionic>release ach>
postganglionic>release NE>binds to
adrenergic>alpha and beta
Refer to cheat sheet on page 481
2
3
Peripheral Nervous System
•Somatic nervous system – voluntary control over
skeletal muscle
•Autonomic nervous system – involuntary control
over the contraction of smooth muscle, cardiac
muscle, gland secretion
4
Receptors in the autonomic nervous system
• Diagram needed
5
Autonomic Nervous System (ANS)
• Sympathetic – “flight or fight”
• Ready for immediate stress
• Increase of body systems
• Parasympathetic – “rest and digest”
• Nonstressful conditions
• Decrease body systems
• Digestion increased
6
7
8
Synapse
•Communication between neurons, muscles and
glands
•Connection of neurons
•Synapse – end point of one neuron junction
(presynaptic), synaptic cleft, and start of new
neuron (postsynaptic)
9
Drug Effects
•Affect synthesis of
neurotransmitters
•Prevent storage of
neurotransmittters
•Influence the release of
neurotransmitters
•Bind to the receptor site of
postsynaptic neuron – increase
autonomic function
10
ANS Neurotransmitters
• Acetylcholine (Ach) – released by
cholinergic nerves
• Nicotinic receptors – Ach receptors in the
preganglionic ganglia, effects similar to
effects of nicotine (parasympathetic)
• Muscarinic receptors – Ach receptors in
postganglionic ending in target tissues,
similar to effects of amanita muscaria
11
ANS Transmitters
•Alpha receptors –
• alpha1 (vasoconstriction)
•decrease GI motility, elevate BP,
mydriasis
•alpha 2 (smooth muscle
constriction) beta 1 (Positive
chronotropic) increases HR
(Positive inotropic) contractility
•beta 2 (Bronchodilator) lungs
12
Neurotransmitter Disintegration
•Ach
•Destroyed by
acetylcholinesterase
•Norepinephrine (NE)
•Reuptake of NE into nerve
terminals for reuse
•Inactivation by monoamine
oxidase (MAO)
13
Baroreceptor Reflex (negative feedback)
The baroreceptor reflex regulates
BP
•The receptors are located in the
carotid sinus and aortic arch
•The brain sends impulses to the
ANS
•When there is a decrease in BP
there is vasoconstriction and an
increase in CO
•When there is an increase in BP
vasodilation and a decrease in
BP
14
Autonomic Drug Classes
•Sympathomimetics or adrenergic agonists –
stimulate sympathetic system (SNS)
•Parasympathomimetics or muscarinic agonists –
stimulate parasympathetic system (PNS)
15
Autonomic Drug Classes
•Adrenergic antagonists or adrenergic blockers –
inhibit SNS
•Anticholinergics or parasympatholytics or
muscarinic blockers – inhibit PNS
16
Parasympathomimetics
•AKA – cholinergic agents
•Cholinergic = parasympathetic
•Classic – acetylcholine
•Does not stay long in body, rapidly destroyed after
receptor binding
•Direct acting – bind to cholinergic receptors to
produce rest/digest response – AKA muscarinic
agonist
•Indirect acting – avoids destruction of Ach and
allow to remain on cholinergic receptors for longer
time – AKA cholinesterase inhibitors
17
Muscarinic Agonists or
Parasympathomimetics
•Muscarinic agonist = cholinergic agent
•Causes receptor activation
•The prototype is Bethanechol/
Urecholine
•Reversibly binds to muscarinic
cholingeric receptors
•Relief of urinary retention
postoperatively and post-partum
18
Adverse effects of Bethanechol
•Hypotension
•Bradycardia
•Increased secretions
•Exacerbation of asthma
19
Other Parasympathomimetic Drugs
•Cevimeline/ Evoxac – tx of dry
mouth
•Pilocarpine/ Isopto Carpine – used
for tx of glaucoma (decreases
presssure)
•Acetycholine – minimal therapeutic
use – too rapid destruction
20
Nursing Management
Parasympathetic Medications
•Watch for adverse effects:
•CI – Lithium:
 increase CNS depression
taken together
•CI – Adenosine :
increase chance heart block
•Elderly – CNS stimulation:
 Mistaken belief that symptoms may
be effects of old age or age‐related
illness
21
Parasympathomimetics
•Cholinesterase Inhibitors (indirect acting)
•Also known as anticholinesterases
•Prevents the breakdown of Ach which leads to a
subsequent increase of ACh at all junctions where
ACh is effective
•Classified as reversible and irreversible
22
Uses of Cholinesterase Inhibitors
•Treatment of Myasthenia
gravis (increase strength by
increasing neuromuscular
transmission)
•Reverse the effects of
neuromuscular blockade
•Occurs naturally in
venoms/poisons
•Can be used as nerve gas
23
Myasthenia Gravis
•Ptosis
•Difficulty swallowing
•Weakness of skeletal
muscles
•Anticholinesterases
will increase Ach at
the NMJ and increase
muscle strength
24
Cholinesterase Inhibitors also called
acetylcholinesterase Inhibitor
•Increases acetylcholine
•Increases glandular secretions
•Bradycardia
•Bronchial constriction
•Increased motility of GI smooth muscle
•Mild CNS stimulation with regular
doses; depression of CNS with toxic
levels
•Take this medication at the same time
every day
25
Precautions and Contraindications
with Acetylcholinesterase inhibitors
Increases acetylcholine levels (sludge)
Not that it will cause, just be cautious with
these patient:
• Obstruction of GI tract
• Obstruction of the urinary tract
• Peptic ulcer disease
• Asthma-bronchial constriction
• Coronary insufficiency
26
Common Names
•Neostigmine/ Prostigmin
•Physostigmine/ Antilirium
•Edrophonium/ Tensilon
•Pyridostigmine/ Mestinon
•Donepezil/ Aricept
27
Cholinergic and Myasthenic Crisis
•Cholinergic
•Profuse secretions
•Laryngospasm
•Bronchoconstriction
•Convulsions
•Paralysis
•Caused by overdose of
medications or exacerbation
of Myastenia Gravis
28
Cholinergic and Myasthenic Crisis
•Myasthenic crisis
•Extreme muscle weakness
•Caused by worsening of disease
•Edrophonium/ Tensilon challenge;
if the symptoms are alleviated this is
a Myasthenic crisis; if symptoms
intensified cholinergic crisis
If increasing the meds decreases
the s/s=Dz. was the problem. No
change=meds are the problem
29
Treatment of Cholinergic or Myasthenic crisis
•Cholinergic Crisis
•Atropine anticholinergic
•Ventilatory support
•Withhold the offending
agent
30
Nursing Management of Cholinergic or
Myasthenic crisis
• CI – mechanical obstruction of GI and
urinary
• Build-up of Ach at junction sites
•
•
•
•
•
•
Profuse salivation
Increased muscle tone
Urinary frequency
Bronchoconstriction
Bradycardia
SLUDGE=salivation, lacrimation,
urination, diaphoresis, GI, emesis
31
Uses of Neuromuscular Blocking Agents
Muscle relaxation/paralysis via
inhibition of acetylcholine:
ACH cause constriction so
blocking it=relaxation
•Facilitation of mechanical
ventilation
•Facilitation of endotracheal
intubation
•Diagnosis of myasthenia gravis
32
Muscarinic Antagonists/ Parasympatholytic Drugs/
Antimuscarinic Drugs/ Muscarinic Blockers
Blocks ACH, opposite of sludge
•AKA Anticholinergic/ cholinergic
blockers
•Competitively blocks the actions of Ach
•The prototype is Atropine (blocks
muscarinic)
•Given for the treatment of– preanesthetic use to decrease secretions,
disorders of the eye, bradycardia,
intestinal hypermotility, muscarinic
agonist poisoning .
33
34
Adverse effects of Atropine
•Xerostomia (dry mouth)
•Blurred vision
•Increase IOP (blocks
ach=increased
pressure)
•Urinary retention
•Constipation
•Tachycardia
•Anhidrosis – abnormal
deficiency of sweat
35
Other Anticholinergics
•Oxybutynin/ Ditropan and Detrol
– tx urinary incontinence=blocks
ach to decrease urination
•*Glycopyrrolate/ Robinul – “dry”
field pre-anesthesia (respiratory
secretions diminished)
•Scopolamine – motion sickness
•Ipratroprium bromide – tx
of asthma (blocks ach=
bronchodilation)
36
Atropine (Anti-Cholinergic) uses
Atropine given to treat:(blocks parasympathetic)
Muscarinic poisoning
• Caused by direct-acting muscarinic
agonists and anticholinesterases
• (SLUDGE) Symptoms are produced by
excessive activation of muscarinic
receptors
• Supportive therapy
• Atropine is the drug of choice for
bradycardia and cholinergic crisi
37
Anti-muscarinic Poisoning-Blocks ACH
Too much atropine
Atropine is an antimuscarinic/Anti-cholinergic
Overdose of Anti-muscarinic:
•Caused by some antimuscarinic drugs
•Symptoms are due to
blockade of muscarinic
receptors
38
Treatment of Anti-muscarinic Poisoning
•Minimize absorption of
antimuscarinic agent- ipecac and
activated charcoal
•Give antidote• Physostigmine acts by interfering
with the metabolism of
acetylcholine. Given to treat
atropine over dose
or any other anti-cholinergic crisis
39
Some Important Terms
Muscarinic crisis-Abdominal pain, diarrhea, nausea, vomiting, lacrimation, blurred
vision, bronchial hypersecretion due to parasympathetic hyperresponse
Cholinergic Crisis-An over-stimulation at a neuromuscular junction due to an excess
of acetylcholine (ACh), as of a result of the inactivity (perhaps even inhibition) of
acetylcholinesterase, caused by nerve gas, in patients with myasthenia gravis who
have overdosed on cholinergic agents, or in surgical candidates, due to an excess of
cholinesterase inhibitor given to reverse surgical muscle paralysis
Myastenia gravis- is treated with cholinergic drugs in attempt to decrease muscle
weakness. Cholinergic drugs increase aceytcholine which stimulates muscles and
decreases muscle weakness. Overdose of this drug, or adverse effects of this drug
would result in a cholinergic crisis
Myasthenic crisis-An acute ↑ in requirement for anticholinesterase therapy or
refractoriness to same, diagnosed by a Tensilon test, with transient ↓ of symptoms
Nicotinic crisis-Muscle weakness, fasciculations, cramping and dysphagia, due to
over depolarization at the neuromuscular junction.
40
Mustard Gas Poisoning
41
Indications of Adrenergic Agonists or
Sympathomimetics
•Stimulates alpha 1
Give for treatment of:
•Hemostasis
•Nasal decongestant
•Decreased BP
•Miosis
42
Indications of Adrenergic Agonists or
Sympathomimetics
•Alpha 2
•No clinical significance in the
periphery
•Centrally there is decrease
sympathetic outflow
•Smooth muscle constriction
43
Adverse effects of Alpha 1
•Hypertension due to
vasoconstriction
•Necrosis of tissues
because of lack of blood
flow due to vasoconstriction
•Tachycardia
44
Indications of Adrenergic Agonists
•Beta 1
•Cardiac arrest
•Heart failure
•Shock
•Atrioventricular block
45
Indications of Adrenergic Agonists
Beta 2
•Asthma (bronchodilates)
•Delay of pre-term labor
(relaxes uterine muscles)
46
Adrenergic Agonists
Adverse Effects
•Beta 1
•Tachycardia
•Angina pectoris
47
Adrenergic Agonists
Adverse Effects
Beta 2 agonist
•Hyperglycemia
•Tremor
48
Indications for Epinephrine Usage
•Treatment of choice for anaphylaxis
•Alpha and beta adrenergic
•AV block
•During cardiac arrest
•Decrease BP
•Bronchoconstriction
49
Adverse effects of Epinephrine
•Hypertensive crisis
•Dysrhythmias
•Angina pectoris
•Hyperglycemia
•Necrosis
50
Adrenergic Agonists/ Receptors Stimulated
•Isoproterenol: Beta 1 and 2
•Dopamine: Dopamine, Beta 1,
and Alpha 1 at high doses
•Dobutamine: Beta 1
•Phenylephrine: Alpha 1
•Terbutaline: Beta 2
•Ephedrine: Alpha 1nd 2, Beta 1
and 2
51
Indications (reason to give) of Adrenergic
Antagonists
Blocks Sympathetic
•Essential hypertension
•Benign prostatic
hyperplasia (BPH)
•Pheocromocytoma
•Raynaud’s disease
(decreased circulation
from vasoconstriction)
52
Adverse Effects of
Alpha Adrenergic Antagonists
Blocks sympathetic
•Orthostatic hypotension
•Reflex tachycardia
•Nasal congestion
53
Adrenergic - Uses
•Prazosin- HTN
•Terazosin- HTN and BPH_
•Doxazosin- HTN and BPH
•Tamsulosin- BPH
•Phentolamine-vasodilation
54
Therapeutic Indications (reason to use)of Beta
Adrenergic Antagonists
•Angina pectoris
•Hypertension
•Cardiac Dysrhythmias
55
Adverse Effects of Beta Adrenergic
Antagonists
Beta 1 blocked Causes:
•Bradycardia
•Reduced cardiac output
•Precipitation of heart failure
•AV heart block
•Rebound cardiac excitation
56
Adverse Effects of Beta Adrenergic
Antagonists
Beta 2 Blocked Causes:
•Bronchoconstriction
•Inhibition of
glycogenolysis (increased
blood sugar)
57
Beta Blockers
•Propanolol
•Non-selective beta
blocker
•Used for HTN, angina,
cardiac dysrhythmias,
and MI
•Metoprolol
•Selective beta 1
blocker at therapeutic
doses
•Used for HTN,
angina, heart failure,
and MI
58
59