Chapter 20
Cholinergic Drugs
Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Cholinergic Drugs

Drugs that stimulate the parasympathetic
nervous system (PSNS)

The PSNS is the opposing system to
the sympathetic nervous system (SNS)
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Cholinergic Drugs (cont’d)


Also known as cholinergic agonists or
parasympathomimetics
Mimic effects of the PSNS neurotransmitter
acetylcholine (ACh)
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Cholinergic Receptors

Two types, determined by:




Location
Action once stimulated
Nicotinic receptors
Muscarinic receptors
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Nicotinic Receptors


Located in the ganglia of both the
PSNS and SNS
Named nicotinic because they can be stimulated
by the alkaloid nicotine
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Muscarinic Receptors

Located postsynaptically in the effector organs
of the PSNS

Smooth muscle
 Cardiac muscle
 Glands

Named muscarinic because they can be
stimulated by the alkaloid muscarine
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Cholinergic Drugs:
Mechanism of Action

Direct-acting cholinergic agonists


Bind to cholinergic receptors, activating them
Indirect-acting cholinergic agonists


Inhibit the enzyme acetylcholinesterase, which breaks
down ACh
Results in more ACh available at the receptors
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Indirect-Acting
(Cholinesterase Inhibitors)

Reversible


Bind to cholinesterase for a period of
minutes to hours
Irreversible


Bind to cholinesterase and form a permanent
covalent bond
The body must make new cholinesterase to break
these bonds
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Drug Effects


Effects seen when PSNS is stimulated
The PSNS is the “rest and digest” system
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Drug Effects (cont’d)

Stimulate intestine and bladder




Stimulate pupils



Increased gastric secretions
Increased gastrointestinal motility
Increased urinary frequency
Constriction (miosis)
Reduced intraocular pressure
Increased salivation and sweating
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Cholinergic Drug Effects (cont’d)

Cardiovascular effects



Decreased heart rate
Vasodilation
Respiratory effects

Bronchial constriction, narrowed airways
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Cholinergic Drug Effects (cont’d)




At recommended doses, cholinergics primarily
affect muscarinic receptors
At high doses, cholinergics stimulate nicotinic
receptors
Desired effects are from muscarinic receptor
stimulation
Many undesirable effects are caused by
stimulation of nicotinic receptors
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Classroom Response Question
The nurse is assessing a patient who has been taking a
cholinergic drug for 3 days. The patient has flushed skin,
orthostatic blood pressure changes, and is complaining of
abdominal cramps and nausea. The nurse recognizes that
the patient is most likely experiencing
A.
B.
C.
D.
early signs of a cholinergic crisis.
late signs of a cholinergic crisis.
an allergic reaction to the drug.
expected adverse effects.
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Indications

Direct-acting drugs



Reduce intraocular pressure
Useful for glaucoma and intraocular surgery
• echothiophate
• carbachol
• pilocarpine
Topical application because of poor oral absorption
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Indications (cont’d)

Direct-acting drug—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 subcutaneous injection
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Indications (cont’d)

Indirect-acting drugs

Cause skeletal muscle contractions
 Used for diagnosis and treatment of
myasthenia gravis
 Used to reverse neuromuscular blocking drugs
 Used to reverse anticholinergic poisoning (antidote)
• Examples: physostigmine, pyridostigmine
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Indications (cont’d)

Indirect-acting anticholinesterase drugs

Used for treatment of mild to moderate Alzheimer’s
disease
• donepezil (Aricept)
• galantamine (Razadyne)
• rivastigmine (Exelon)
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Indications (cont’d)

memantine (Namenda)


Not a cholinergic drug
Also used in the treatment of Alzheimer’s disease
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Adverse Effects


Adverse effects are a result of overstimulation of
the PSNS
Cardiovascular


CNS


Bradycardia, hypotension, syncope, conduction
abnormalities (AV block and cardiac arrest)
Headache, dizziness, convulsions, ataxia
Gastrointestinal

Abdominal cramps, increased secretions, nausea,
vomiting
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Adverse Effects (cont’d)

Respiratory


Increased bronchial secretions, bronchospasms
Other

Lacrimation, sweating, salivation, miosis
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Interactions

Anticholinergics, antihistamines,
sympathomimetics


Antagonize cholinergic drugs, resulting in decreased
responses
Other cholinergic drugs

Additive effects
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Herbal Products: Gingko

Common uses





Prevent memory loss
Vertigo
Tinnitus
May cause GI upset, headache, bleeding
Potential interactions




Aspirin
NSAIDs
Anticoagulants
Anticonvulsants
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Classroom Response Question
A 60-year-old woman asks the nurse about taking ginkgo to
help with her memory. The patient has a history of arthritis,
type 2 diabetes, thyroid disease, and hypertension. She is
currently taking NSAIDs for arthritis, oral antidiabetic
medications, thyroid replacement hormone, and a beta
blocker for blood pressure. What potential adverse effect
from the gingko would be of most concern for this patient?
A.
B.
C.
D.
Stomach upset
Diarrhea
Bleeding
Drowsiness
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Nursing Implications



Note that these drugs 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 vital signs and
systems overview
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Nursing Implications (cont’d)



Medications should be taken as ordered
and not abruptly stopped
Doses should be spread evenly apart
to optimize the effects of the medication
Overdosing can cause life-threatening problems.
Patients should not adjust dosages unless
directed by their health care provider
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Classroom Response Question
A patient is scheduled to have lunch at 1200. The
nurse will administer the pyridostigmine (Mestinon)
at what time for optimal therapeutic effect?
A. 1100
B. 1130
C. 1200
D. 1230
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Nursing Implications (cont’d)



Encourage patients with myasthenia gravis to
take medication 30 minutes before eating to help
improve chewing and swallowing
When cholinergic drugs are prescribed for
Alzheimer’s disease, be honest with caregivers
and patients that the drugs are for management
of symptoms (not a cure)
Therapeutic effects of anti-Alzheimer’s drugs
may not occur for up to 6 weeks
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Classroom Response Question
A patient with Alzheimer’s disease accidentally took 2
weeks’ worth of a cholinergic medication. He is brought to
the emergency department, is going into shock, and
experiencing severe hypotension and vomiting. The nurse
will expect which initial treatment?
A. Administration of physostigmine
B. Administration of atropine
C. Administration of epinephrine
D. Cardiovascular support with dopamine
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Nursing Implications (cont’d)


Atropine is the antidote for cholinergics, and 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
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Nursing Implications (cont’d)

Monitor for therapeutic effects


Alleviated signs and symptoms of myasthenia gravis
In postoperative patients with decreased GI
peristalsis, monitor for:
• Increased bowel sounds
• Passage of flatus
• Occurrence of bowel movements
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Nursing Implications (cont’d)

Monitor for therapeutic effects



In patients with urinary retention/hypotonic bladder,
urination should occur within 60 minutes of
bethanechol administration
In patients with Alzheimer’s disease:
• Improvement in symptoms
• Improvement in mood and decrease in confusion
Monitor for adverse effects
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