cholinergic blockers

Copyright © 2002, 1998, Elsevier Science (USA). All rights reserved.
Drugs Affecting theDrugs Affecting the
Autonomic Nervous SystemAutonomic Nervous System
Cholinergic Agents andCholinergic Agents and
Cholinergic Blocking AgentsCholinergic Blocking Agents

Cholinergic AgentsCholinergic Agents
• Drugs that stimulate theDrugs that stimulate the
parasympathetic nervous system (PSNS)parasympathetic nervous system (PSNS)
• The PSNS is the opposing system toThe PSNS is the opposing system to
the SNSthe SNS

Also known asAlso known as
• cholinergic agonistscholinergic agonists
oror
• parasympathomimeticsparasympathomimetics

Instructors may wish to useInstructors may wish to use
EIC Image #56:EIC Image #56:
The Parasympathetic andThe Parasympathetic and
Sympathetic Nervous SystemsSympathetic Nervous Systems
andand
Their Relationships to One AnotherTheir Relationships to One Another

• Mimic the effects of the PSNSMimic the effects of the PSNS
neurotransmitterneurotransmitter
• Acetylcholine (ACh)Acetylcholine (ACh)

Cholinergic ReceptorsCholinergic Receptors
Two types, determined by:Two types, determined by:
• LocationLocation
• Action once stimulatedAction once stimulated
Nicotinic receptors and Muscarinic receptorsNicotinic receptors and Muscarinic receptors

Nicotinic ReceptorsNicotinic Receptors
• Located in the ganglia of both theLocated in the ganglia of both the
PSNS and SNSPSNS and SNS
• Named “nicotinic” because can be stimulatedNamed “nicotinic” because can be stimulated
by the alkaloid nicotineby the alkaloid nicotine

Muscarinic ReceptorsMuscarinic Receptors
• Located postsynaptically:Located postsynaptically:
– Smooth muscleSmooth muscle
– Cardiac muscleCardiac muscle
– Glands of parasympathetic fibersGlands of parasympathetic fibers
– Effector organs of cholinergic sympathetic fibersEffector organs of cholinergic sympathetic fibers
• Named “muscarinic” because can beNamed “muscarinic” because can be
stimulated by the alkaloid muscarinestimulated by the alkaloid muscarine

Instructors may wish toInstructors may wish to
insert EIC Image #57:insert EIC Image #57:
The Sympathetic, Parasympathetic,The Sympathetic, Parasympathetic,
and Somatic Nervous Systemsand Somatic Nervous Systems
This slide illustrates location of the nicotinicThis slide illustrates location of the nicotinic
and muscarinic receptors within the PSNS.and muscarinic receptors within the PSNS.

Adrenergic Agents:Adrenergic Agents:
Mechanism of ActionMechanism of Action
• Direct-acting (agonist)Direct-acting (agonist)
– Bind to cholinergic receptors, causing stimulationBind to cholinergic receptors, causing stimulation

Adrenergic Agents:Adrenergic Agents:
• Indirect-actingIndirect-acting
– Inhibit the enzyme “cholinesterase”Inhibit the enzyme “cholinesterase”
Result: more ACh is available at the receptorsResult: more ACh is available at the receptors

Indirect-Acting Cholinergic AgentsIndirect-Acting Cholinergic Agents
(Cholinesterase Inhibitors)(Cholinesterase Inhibitors)
• ReversibleReversible
– Bind to cholinesterase for a period ofBind to cholinesterase for a period of
minutes to hoursminutes to hours
• IrreversibleIrreversible
– Bind to cholinesterase and form a permanentBind to cholinesterase and form a permanent
covalent bondcovalent bond
– The body must make new cholinesteraseThe body must make new cholinesterase

Drug Effects of Cholinergic AgentsDrug Effects of Cholinergic Agents
• Effects seen when the PSNS is stimulated.Effects seen when the PSNS is stimulated.
• The PSNS is the “rest and digest” system.The PSNS is the “rest and digest” system.

““SLUDGE”SLUDGE”
• SSalivationalivation
• LLacrimationacrimation
• UUrinary incontinencerinary incontinence
• DDiarrheaiarrhea
• GGastrointestinal crampsastrointestinal cramps
• EEmesismesis

• Stimulate intestine and bladderStimulate intestine and bladder
– Increased gastric secretionsIncreased gastric secretions
– Increased gastrointestinal motilityIncreased gastrointestinal motility
– Increased urinary frequencyIncreased urinary frequency
• Stimulate pupilStimulate pupil
– Constriction (miosis)Constriction (miosis)
– Reduced intraocular pressureReduced intraocular pressure
• Increased salivation and sweatingIncreased salivation and sweating

• Cardiovascular effectsCardiovascular effects
– Decreased heart rateDecreased heart rate
– VasodilationVasodilation
• Respiratory effectsRespiratory effects
– Bronchial constriction, narrowed airwaysBronchial constriction, narrowed airways

• At recommended doses, the cholinergicsAt recommended doses, the cholinergics
primarily affect the MUSCARINIC receptors.primarily affect the MUSCARINIC receptors.
• At high doses, cholinergics stimulate theAt high doses, cholinergics stimulate the
NICOTINIC receptors.NICOTINIC receptors.

• DESIRED EFFECTS: from muscarinicDESIRED EFFECTS: from muscarinic
receptor stimulationreceptor stimulation
• Many undesirable effects are due toMany undesirable effects are due to
stimulation of the nicotinic receptorsstimulation of the nicotinic receptors

Cholinergic Agents:Cholinergic Agents:
Therapeutic UsesTherapeutic Uses
Direct-Acting AgentsDirect-Acting Agents
• Reduce intraocular pressureReduce intraocular pressure
• Useful for glaucoma and intraocular surgeryUseful for glaucoma and intraocular surgery
Examples: acetylcholine, carbachol, pilocarpineExamples: acetylcholine, carbachol, pilocarpine
Topical application due to poor oral absorptionTopical application due to poor oral absorption

Direct-Acting Agent—bethanecholDirect-Acting Agent—bethanechol
• Increases tone and motility of bladder and GI tractIncreases tone and motility of bladder and GI tract
• Relaxes sphincters in bladder and GI tract, allowingRelaxes sphincters in bladder and GI tract, allowing
them to emptythem to empty
• Helpful for postsurgical atony of the bladderHelpful for postsurgical atony of the bladder
and GI tractand GI tract
Oral dose or SC injectionOral dose or SC injection

Indirect-Acting AgentsIndirect-Acting Agents
• Cause skeletal muscle contractionsCause skeletal muscle contractions
• Used for diagnosis and treatment ofUsed for diagnosis and treatment of
myasthenia gravismyasthenia gravis
• Used to reverse neuromuscular blocking agentsUsed to reverse neuromuscular blocking agents
• Used to reverse anticholinergic poisoning (antidote)Used to reverse anticholinergic poisoning (antidote)
Examples: physostigmine, pyridostigmineExamples: physostigmine, pyridostigmine

Indirect-Acting Agent—donepezil (Aricept)Indirect-Acting Agent—donepezil (Aricept)
• Used in the treatment of mild to moderateUsed in the treatment of mild to moderate
Alzheimer’s disease.Alzheimer’s disease.
• Helps to increase or maintain memory andHelps to increase or maintain memory and
learning capabilities.learning capabilities.

Cholinergic Agents: Side EffectsCholinergic Agents: Side Effects
Side effects are a result of overstimulationSide effects are a result of overstimulation
of the PSNS.of the PSNS.
• Cardiovascular:Cardiovascular:
– Bradycardia, hypotension, conductionBradycardia, hypotension, conduction
abnormalities (AV block and cardiac arrest)abnormalities (AV block and cardiac arrest)
• CNS:CNS:
– Headache, dizziness, convulsionsHeadache, dizziness, convulsions
• Gastrointestinal:Gastrointestinal:
– Abdominal cramps, increased secretions,Abdominal cramps, increased secretions,
nausea, vomitingnausea, vomiting

Cholinergic Agents: Side EffectsCholinergic Agents: Side Effects
Side effects are a result ofSide effects are a result of
overstimulation of the PSNS.overstimulation of the PSNS.
• Respiratory:Respiratory:
– Increased bronchial secretions, bronchospasmsIncreased bronchial secretions, bronchospasms
• Other:Other:
– Lacrimation, sweating, salivation, loss ofLacrimation, sweating, salivation, loss of
binocular accommodation, miosisbinocular accommodation, miosis

Cholinergic Agents: InteractionsCholinergic Agents: Interactions
• Anticholinergics, antihistamines,Anticholinergics, antihistamines,
sympathomimeticssympathomimetics
• Antagonize cholinergic agents, resultingAntagonize cholinergic agents, resulting
in decreased responsesin decreased responses

Nursing ImplicationsNursing Implications
• Keep in mind that these agents will stimulateKeep in mind that these agents will stimulate
the PSNS and mimic the action of ACh.the PSNS and mimic the action of ACh.
• Assess for allergies, presence of GI or GUAssess for allergies, presence of GI or GU
obstructions, asthma, peptic ulcer disease,obstructions, asthma, peptic ulcer disease,
or coronary artery disease.or coronary artery disease.
• Perform baseline assessment of VS andPerform baseline assessment of VS and
systems overview.systems overview.

• Medications should be taken as orderedMedications should be taken as ordered
and not abruptly stopped.and not abruptly stopped.
• The doses should be spread evenly apartThe doses should be spread evenly apart
to optimize the effects of the medication.to optimize the effects of the medication.
• Overdosing can cause life-threateningOverdosing can cause life-threatening
problems. Patients should not adjust theproblems. Patients should not adjust the
dosages unless directed by the physician.dosages unless directed by the physician.

• Encourage patients with myasthenia gravis toEncourage patients with myasthenia gravis to
take medication 30 minutes before eating totake medication 30 minutes before eating to
help improve chewing and swallowing.help improve chewing and swallowing.
• When donepezil is prescribed for Alzheimer’sWhen donepezil is prescribed for Alzheimer’s
disease, be honest with caregivers anddisease, be honest with caregivers and
patients that the drug is for managementpatients that the drug is for management
of symptoms, not for a cure.of symptoms, not for a cure.
• Therapeutic effects of donepezil may notTherapeutic effects of donepezil may not
occur for up to 6 weeks.occur for up to 6 weeks.

• Atropine is the antidote for cholinergics.Atropine is the antidote for cholinergics.
It should be available in the patient’s roomIt should be available in the patient’s room
for immediate use if needed.for immediate use if needed.
• Patients should notify their physician if theyPatients should notify their physician if they
experience muscle weakness, abdominalexperience muscle weakness, abdominal
cramps, diarrhea, or difficulty breathing.cramps, diarrhea, or difficulty breathing.

Monitor for side effects, including:Monitor for side effects, including:
Increased respiratoryIncreased respiratory Abdominal crampingAbdominal cramping
secretionssecretions
BronchospasmsBronchospasms DysrhythmiasDysrhythmias
Difficulty breathingDifficulty breathing HypotensionHypotension
Nausea and vomitingNausea and vomiting BradycardiaBradycardia
DiarrheaDiarrhea Increased sweatingIncreased sweating
Increase in frequency andIncrease in frequency and
urgency of voiding patternsurgency of voiding patterns

Monitor for therapeutic effects:Monitor for therapeutic effects:
• Alleviated signs and symptoms of myasthenia gravisAlleviated signs and symptoms of myasthenia gravis
• In postoperative patients with decreased GIIn postoperative patients with decreased GI
peristalsis, look for:peristalsis, look for:
– Increased bowel soundsIncreased bowel sounds
– Passage of flatusPassage of flatus
– Occurrence of bowel movementsOccurrence of bowel movements
• In patients with urinary retention/hypotonic bladder,In patients with urinary retention/hypotonic bladder,
urination should occur within 60 minutes ofurination should occur within 60 minutes of
bethanecol administrationbethanecol administration

• Drugs that block or inhibit the actions ofDrugs that block or inhibit the actions of
acetylcholine (ACh) in the parasympatheticacetylcholine (ACh) in the parasympathetic
nervous system (PSNS)nervous system (PSNS)

Cholinergic Blocking Agents:Cholinergic Blocking Agents:
• Competitive antagonistsCompetitive antagonists
• Compete with AChCompete with ACh
• Block ACh at the muscarinic receptorsBlock ACh at the muscarinic receptors
in the PSNSin the PSNS
– As a result, ACh is unable to bind to theAs a result, ACh is unable to bind to the
receptor site and cause a cholinergic effect.receptor site and cause a cholinergic effect.

• Once these drugs bind to receptors, theyOnce these drugs bind to receptors, they
inhibit nerve transmission at these receptors.inhibit nerve transmission at these receptors.

Instructors may wish to useInstructors may wish to use
EIC Image #58:EIC Image #58:
Site of Action of Cholinergic BlockersSite of Action of Cholinergic Blockers
Within the PSNSWithin the PSNS

Chemical ClassChemical Class
NaturalNatural Synthetic/SemisyntheticSynthetic/Semisynthetic
atropineatropine anisotropineanisotropine clidiniumclidinium
belladonnabelladonna dicyclominedicyclomine glycopyrrolateglycopyrrolate
hyoscyaminehyoscyamine hexocycliumhexocyclium homatropinehomatropine
scopolaminescopolamine ipratropiumipratropium isopropamideisopropamide
oxybutyninoxybutynin propanthelinepropantheline
tolterodinetolterodine tridihexethyltridihexethyl

Drug Effects ofDrug Effects of
• CardiovascularCardiovascular
– Small doses: decrease heart rateSmall doses: decrease heart rate
– Large doses: increase heart rateLarge doses: increase heart rate
• CNSCNS
– Small doses: decrease muscle rigiditySmall doses: decrease muscle rigidity
and tremorsand tremors
– Large doses: drowsiness, disorientation,Large doses: drowsiness, disorientation,
hallucinationshallucinations

• EyeEye
– Dilated pupils (mydriasis)Dilated pupils (mydriasis)
– Decreased accommodation due to paralysisDecreased accommodation due to paralysis
of ciliary muscles (cycloplegia)of ciliary muscles (cycloplegia)
• GastrointestinalGastrointestinal
– Relax smooth muscle tone of GI tractRelax smooth muscle tone of GI tract
– Decrease intestinal and gastric secretionsDecrease intestinal and gastric secretions
– Decrease motility and peristalsisDecrease motility and peristalsis

• GenitourinaryGenitourinary
– Relaxed detrusor muscleRelaxed detrusor muscle
– Increased constriction of internal sphincterIncreased constriction of internal sphincter
– Result: urinary retentionResult: urinary retention
• GlandularGlandular
– Decreased bronchial secretions, salivation,Decreased bronchial secretions, salivation,
sweatingsweating
• RespiratoryRespiratory
– Decreased bronchial secretionsDecreased bronchial secretions
– Dilated bronchial airwaysDilated bronchial airways

CNSCNS
Decreased muscle rigidity and muscle tremorsDecreased muscle rigidity and muscle tremors
• Parkinson’s diseaseParkinson’s disease
• Drug-induced extrapyramidal reactionsDrug-induced extrapyramidal reactions

CardiovascularCardiovascular
Affect the heart’s conduction systemAffect the heart’s conduction system
• Low doses: slow the heart rateLow doses: slow the heart rate
• High doses: block inhibitory vagal effects onHigh doses: block inhibitory vagal effects on
the SA and AV node pacemaker cellsthe SA and AV node pacemaker cells
– Result: increased heart rateResult: increased heart rate

AtropineAtropine
Used primarily for cardiovascular disordersUsed primarily for cardiovascular disorders
• Sinus node dysfunctionSinus node dysfunction
• Symptomatic second-degree heart blockSymptomatic second-degree heart block
• Sinus bradycardia with hemodynamic compromiseSinus bradycardia with hemodynamic compromise
(advanced life support)(advanced life support)

RespiratoryRespiratory
Blocking the cholinergic stimulation of the PSNSBlocking the cholinergic stimulation of the PSNS
allows unopposed action of the SNS.allows unopposed action of the SNS.
• Results:Results:
– Decreased secretions from nose, mouth,Decreased secretions from nose, mouth,
pharynx, bronchipharynx, bronchi
– Relaxed smooth muscles in bronchiRelaxed smooth muscles in bronchi
and bronchiolesand bronchioles
– Decreased airway resistanceDecreased airway resistance
– BronchodilationBronchodilation

Respiratory agents are used to treat:Respiratory agents are used to treat:
• Exercise-induced bronchospasmsExercise-induced bronchospasms
• Chronic bronchitisChronic bronchitis
• AsthmaAsthma
• Chronic obstructive pulmonary diseaseChronic obstructive pulmonary disease

GastrointestinalGastrointestinal
PSNS controls gastric secretions and smoothPSNS controls gastric secretions and smooth
muscles that produce gastric motility.muscles that produce gastric motility.
• Blockade of PSNS results in:Blockade of PSNS results in:
– Decreased secretionsDecreased secretions
– Relaxation of smooth muscleRelaxation of smooth muscle
– Decreased GI motility and peristalsisDecreased GI motility and peristalsis

Gastrointestinal agents are used to treat:Gastrointestinal agents are used to treat:
• Peptic ulcer diseasePeptic ulcer disease
• Irritable bowel diseaseIrritable bowel disease
• GI hypersecretory statesGI hypersecretory states

GenitourinaryGenitourinary
• Relaxed detrusor muscles of the bladderRelaxed detrusor muscles of the bladder
• Increased constriction of the internalIncreased constriction of the internal
sphinctersphincter
• Reflex neurogenic bladderReflex neurogenic bladder
• IncontinenceIncontinence

Side EffectsSide Effects
Body SystemBody System Side/Adverse EffectsSide/Adverse Effects
CardiovascularCardiovascular Increased heart rate,Increased heart rate,
dysrhythmiasdysrhythmias
CNSCNS CNS excitation, restlessness,CNS excitation, restlessness,
irritability, disorientation,irritability, disorientation,
hallucinations, deliriumhallucinations, delirium

EyeEye Dilated pupils, decreasedDilated pupils, decreased
visual accommodation,visual accommodation,
increased intraocular pressureincreased intraocular pressure
GastrointestinalGastrointestinal Decreased salivation,Decreased salivation,
decreased gastric secretions,decreased gastric secretions,
decreased motilitydecreased motility

GenitourinaryGenitourinary Urinary retentionUrinary retention
GlandularGlandular Decreased sweatingDecreased sweating
RespiratoryRespiratory Decreased bronchial secretionsDecreased bronchial secretions

InteractionsInteractions
• Antihistamines, phenothiazines,Antihistamines, phenothiazines,
tricyclic antidepressants, MAOIstricyclic antidepressants, MAOIs
• When given with cholinergic blockingWhen given with cholinergic blocking
agents, cause ADDITIVE cholinergicagents, cause ADDITIVE cholinergic
effects, resulting in increased effectseffects, resulting in increased effects

• Keep in mind that these agents will blockKeep in mind that these agents will block
the action of ACh in the PSNS.the action of ACh in the PSNS.
• Assess for allergies, presence of BPH,Assess for allergies, presence of BPH,
glaucoma, tachycardia, MI, CHF, hiatalglaucoma, tachycardia, MI, CHF, hiatal
hernia, and GI or GU obstruction.hernia, and GI or GU obstruction.
• Perform baseline assessment of VSPerform baseline assessment of VS
and systems overview.and systems overview.

• Medications should be taken exactly as prescribedMedications should be taken exactly as prescribed
to have the maximum therapeutic effect.to have the maximum therapeutic effect.
• Overdosing can cause life-threatening problems.Overdosing can cause life-threatening problems.
• Blurred vision may cause problems with drivingBlurred vision may cause problems with driving
or operating machinery.or operating machinery.
• Patients may experience sensitivity to light andPatients may experience sensitivity to light and
may want to wear dark glasses or sunglasses.may want to wear dark glasses or sunglasses.

• When giving ophthalmic solutions, apply pressure toWhen giving ophthalmic solutions, apply pressure to
the inner canthus to prevent systemic absorption.the inner canthus to prevent systemic absorption.
• Dry mouth may occur; can be handled by chewingDry mouth may occur; can be handled by chewing
gum, frequent mouth care, and hard candy.gum, frequent mouth care, and hard candy.
• Check with physician before taking any otherCheck with physician before taking any other
medication, including OTC medications.medication, including OTC medications.
• ANTIDOTE for atropine is physostigmine salicylateANTIDOTE for atropine is physostigmine salicylate
(Antilirium).(Antilirium).

• Anticholinergics may lead to higher risk forAnticholinergics may lead to higher risk for
heat stroke due to effects on heat-regulatingheat stroke due to effects on heat-regulating
mechanisms.mechanisms.
• Teach patients to limit physical exertion, andTeach patients to limit physical exertion, and
avoid high temperatures and strenuousavoid high temperatures and strenuous
exercise.exercise.
• Emphasize the importance of adequate fluidEmphasize the importance of adequate fluid
and salt intake.and salt intake.

• Patients should report the following to theirPatients should report the following to their
physician: urinary hesitancy and/or retention,physician: urinary hesitancy and/or retention,
constipation, palpitations, tremors, confusion,constipation, palpitations, tremors, confusion,
sedation or amnesia, excessive dry mouthsedation or amnesia, excessive dry mouth
(especially if they have chronic lung(especially if they have chronic lung
infections or disease), or feverinfections or disease), or fever

• Monitor for therapeutic effects:Monitor for therapeutic effects:
• For patients with Parkinson’s disease:For patients with Parkinson’s disease:
fewer tremors and decreased salivationfewer tremors and decreased salivation
and droolingand drooling
• For patients with peptic ulcer disease:For patients with peptic ulcer disease:
decreased abdominal paindecreased abdominal pain

Monitor for side effects, including:Monitor for side effects, including:
ConstipationConstipation TachycardiaTachycardia
TremorsTremors ConfusionConfusion
HallucinationsHallucinations SedationSedation
Urinary retentionUrinary retention Hot, dry skinHot, dry skin
FeverFever
CNS depression (occurs with large doses of atropine)CNS depression (occurs with large doses of atropine)

cholinergic blockers

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