Download Drugs Affecting Autonomic Nervous System 2

Drugs Affecting Autonomic
Nervous System 2
Drugs Affecting the Autonomic Nervous
System
• Cholinergic Agents
• Cholinergic Blocking Agents
Cholinergic Agents
• Drugs that stimulate the parasympathetic
nervous system (PSNS)
• The PSNS is the opposing system to
the SNS Also known as cholinergic agonists
or parasympathomimetics
• Mimic the effects of the PSNS
neurotransmitter Acetylcholine (ACh)
Cholinergic Agents
• Drugs that stimulate the
parasympathetic nervous system (PSNS)
• The PSNS is the opposing system to
the SNS
• Also known as cholinergic agonists or
parasympathomimetics
• Mimic the effects of the PSNS neurotransmitter
• Acetylcholine (ACh)
Cholinergic Receptors
Two types, determined by:
• Location
• Action once stimulated
Nicotinic receptors and Muscarinic receptors
Drug Effects of Cholinergic
Agents
“SLUDGE”
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Salivation
Lacrimation
Urinary incontinence
Diarrhea
Gastrointestinal cramps
Emesis
Drug Effects of Cholinergic
Agents
• Stimulate intestine and bladder
– Increased gastric secretions
– Increased gastrointestinal motility
– Increased urinary frequency
• Stimulate pupil
– Constriction (miosis)
– Reduced intraocular pressure
• Increased salivation and sweating
Drug Effects of Cholinergic
Agents
• Cardiovascular effects
– Decreased heart rate
– Vasodilation
• Respiratory effects
– Bronchial constriction, narrowed airways
Cholinergic Agents:
Therapeutic Uses
Direct-Acting Agents
• Reduce intraocular pressure
• Useful for glaucoma and intraocular surgery
Examples: acetylcholine, carbachol, pilocarpine
Topical application due to poor oral absorption
Cholinergic Agents:
Therapeutic Uses
Direct-Acting Agent—bethanechol
• Increases tone and motility of bladder and GI tract
• Relaxes sphincters in bladder and GI tract, allowing
them to empty
• Helpful for postsurgical atony of the bladder
and GI tract
• Oral dose or SC injection
Cholinergic Agents:
Therapeutic Uses
Indirect-Acting Agents
• Cause skeletal muscle contractions
• Used for diagnosis and treatment of
myasthenia gravis
• Used to reverse neuromuscular blocking agents
• Used to reverse anticholinergic poisoning (antidote)
Examples: physostigmine, pyridostigmine
Cholinergic Agents: Side Effects
Side effects are a result of overstimulation
of the PSNS.
• Cardiovascular:
– Bradycardia, hypotension, conduction
abnormalities (AV block and cardiac arrest)
• CNS:
– Headache, dizziness, convulsions
• Gastrointestinal:
– Abdominal cramps, increased secretions,
nausea, vomiting
Cholinergic Agents: Side
Effects
Side effects are a result of
overstimulation of the PSNS.
• Respiratory:
– Increased bronchial secretions,
bronchospasms
• Other:
– Lacrimation, sweating, salivation, loss of
binocular accommodation, miosis
Cholinergic Agents: Interactions
• Anticholinergics, antihistamines,
sympathomimetics
• Antagonize cholinergic agents, resulting
in decreased responses
Cholinergic Agents:
Nursing Implications
• Keep in mind that these agents will
stimulate the PSNS and mimic the action
of ACh.
• Assess for allergies, presence of GI or GU
obstructions, asthma, peptic ulcer disease,
or coronary artery disease.
• Perform baseline assessment of VS and
systems overview.
Cholinergic Agents:
Nursing Implications
• Medications should be taken as ordered
and not abruptly stopped.
• The doses should be spread evenly apart
to optimize the effects of the medication.
• Overdosing can cause life-threatening
problems. Patients should not adjust the
dosages unless directed by the physician.
Cholinergic Agents:
Nursing Implications
• Atropine is the antidote for cholinergics.
It should be available in the patient’s room
for immediate use if needed.
• Patients should notify their physician if
they experience muscle weakness,
abdominal cramps, diarrhea, or difficulty
breathing.
Cholinergic Agents:
Nursing Implications
Monitor for side effects, including:
Increased respiratory
secretions
Abdominal cramping
Bronchospasms
Dysrhythmias
Difficulty breathing
Hypotension
Nausea and vomiting
Bradycardia
Diarrhea
Increased sweating
Increase in frequency and
urgency of voiding patterns
Cholinergic Agents:
Nursing Implications
Monitor for therapeutic effects:
• Alleviated signs and symptoms of myasthenia gravis
• In postoperative patients with decreased GI peristalsis,
look for:
– Increased bowel sounds
– Passage of flatus
– Occurrence of bowel movements
• In patients with urinary retention/hypotonic bladder,
urination should occur within 60 minutes of bethanecol
administration
Cholinergic Blocking Agents
• Drugs that block or inhibit the actions of
acetylcholine (ACh) in the
parasympathetic nervous system (PSNS)
Cholinergic Blocking Agents:
Mechanism of Action
• Competitive antagonists
• Compete with ACh
• Block ACh at the muscarinic receptors
in the PSNS
– As a result, ACh is unable to bind to the
receptor site and cause a cholinergic effect.
Cholinergic Blocking Agents:
Mechanism of Action
• Once these drugs bind to receptors, they
inhibit nerve transmission at these
receptors.
Drug Effects of
Cholinergic Blocking Agents
• Cardiovascular
– Small doses: decrease heart rate
– Large doses: increase heart rate
• CNS
– Small doses: decrease muscle rigidity
and tremors
– Large doses: drowsiness, disorientation,
hallucinations
Drug Effects of
Cholinergic Blocking Agents
• Eye
– Dilated pupils (mydriasis)
– Decreased accommodation due to paralysis
of ciliary muscles (cycloplegia)
• Gastrointestinal
– Relax smooth muscle tone of GI tract
– Decrease intestinal and gastric secretions
– Decrease motility and peristalsis
Drug Effects of
Cholinergic Blocking Agents
• Genitourinary
– Relaxed detrusor muscle
– Increased constriction of internal sphincter
– Result: urinary retention
• Glandular
– Decreased bronchial secretions, salivation,
sweating
• Respiratory
– Decreased bronchial secretions
– Dilated bronchial airways
Cholinergic Blocking Agents:
Therapeutic Uses
CNS
Decreased muscle rigidity and muscle
tremors
• Parkinson’s disease
• Drug-induced extrapyramidal reactions
Cholinergic Blocking Agents:
Therapeutic Uses
Cardiovascular
Affect the heart’s conduction system
• Low doses: slow the heart rate
• High doses: block inhibitory vagal effects on
the SA and AV node pacemaker cells
– Result: increased heart rate
Cholinergic Blocking Agents:
Therapeutic Uses
Atropine
Used primarily for cardiovascular
disorders
• Sinus node dysfunction
• Symptomatic second-degree heart block
• Sinus bradycardia with hemodynamic compromise
(advanced life support)
Cholinergic Blocking Agents:
Therapeutic Uses
Respiratory
Blocking the cholinergic stimulation of the PSNS
allows unopposed action of the SNS.
• Results:
– Decreased secretions from nose, mouth,
pharynx, bronchi
– Relaxed smooth muscles in bronchi
and bronchioles
– Decreased airway resistance
– Bronchodilation
Cholinergic Blocking Agents:
Therapeutic Uses
Respiratory agents are used to treat:
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Exercise-induced bronchospasms
Chronic bronchitis
Asthma
Chronic obstructive pulmonary disease
Cholinergic Blocking Agents:
Therapeutic Uses
Gastrointestinal
PSNS controls gastric secretions and
smooth muscles that produce gastric
motility.
• Blockade of PSNS results in:
– Decreased secretions
– Relaxation of smooth muscle
– Decreased GI motility and peristalsis
Cholinergic Blocking Agents:
Therapeutic Uses
Gastrointestinal agents are used to treat:
• Peptic ulcer disease
• Irritable bowel disease
• GI hypersecretory states
Cholinergic Blocking Agents:
Therapeutic Uses
Genitourinary
• Relaxed detrusor muscles of the
bladder
• Increased constriction of the internal
sphincter
• Reflex neurogenic bladder
• Incontinence
Cholinergic Blocking Agents:
Side Effects
Body System
Side/Adverse Effects
Cardiovascular
Increased heart rate,
dysrhythmias
CNS
CNS excitation, restlessness,
irritability, disorientation,
hallucinations, delirium
Cholinergic Blocking Agents:
Side Effects
Body System
Side/Adverse Effects
Eye
Dilated pupils, decreased visual
increased intraocular pressure
accommodation,
Gastrointestinal
Decreased salivation,
decreased gastric secretions,
decreased motility
Cholinergic Blocking Agents:
Side Effects
Body System
Side/Adverse Effects
Genitourinary
Urinary retention
Glandular
Decreased sweating
Respiratory
Decreased bronchial secretions
Cholinergic Blocking Agents:
Interactions
• Antihistamines.
• When given with cholinergic blocking
agents, cause ADDITIVE cholinergic
effects, resulting in increased effects
Cholinergic Blocking Agents:
Nursing Implications
• Keep in mind that these agents will block
the action of ACh in the PSNS.
• Assess for allergies, presence of BPH,
glaucoma, tachycardia, MI, CHF, hiatal
hernia, and GI or GU obstruction.
• Perform baseline assessment of VS
and systems overview.
Cholinergic Blocking Agents:
Nursing Implications
• Medications should be taken exactly as prescribed
to have the maximum therapeutic effect.
• Overdosing can cause life-threatening problems.
• Blurred vision may cause problems with driving
or operating machinery.
• Patients may experience sensitivity to light and
may want to wear dark glasses or sunglasses.
Cholinergic Blocking Agents:
Nursing Implications
• When giving ophthalmic solutions, apply pressure to the
inner canthus to prevent systemic absorption.
• Dry mouth may occur; can be handled by chewing gum,
frequent mouth care, and hard candy.
• Check with physician before taking any other medication,
including OTC medications.
• ANTIDOTE for atropine is physostigmine salicylate
(Antilirium).
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