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Chapter 20
Cholinergic Drugs
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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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3. Cholinergic Drugs (Cont.)
Also known as cholinergic agonists or parasympathomimetics
Mimic effects of the PSNS neurotransmitter acetylcholine (ACh)
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5. 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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9. Cholinergic Drugs: Mechanism of Action
Direct-acting cholinergic agonists
Bind to cholinergic receptors, activating them
Indirect-acting cholinergic agonists
Also known as cholinesterase inhibitors
Inhibit the enzyme acetylcholinesterase, which breaks down ACh
Results in more ACh available at the receptors
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10. Indirect-Acting (Cholinesterase Inhibitors)
Reversible
Bind to cholinesterase for a short period of time
Irreversible
Bind to cholinesterase for a long period of time
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
Sympathetic nervous system: “flight or fight”
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Drug Effects (Cont.)
Stimulate intestine and bladder
Increased gastric secretions
Increased gastrointestinal motility
Increased urinary frequency
Stimulate pupils
Constriction (miosis)
Reduced intraocular pressure
Increased salivation and sweating
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13. Cholinergic Drug Effects
Cardiovascular effects
Decreased heart rate
Vasodilation
Respiratory effects
Bronchial constriction, narrowed airways
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14. Cholinergic Drug Effects (Cont.)
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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15. Audience Response System Question
The nurse is assessing a patient who has been taking a cholinergic drug for 3 days. The patient has flushed skin and orthostatic blood pressure changes and is complaining of abdominal cramps and nausea. The nurse recognizes that the patient is most likely experiencing
early signs of a cholinergic crisis.
late signs of a cholinergic crisis.
an allergic reaction to the drug.
expected adverse effects.
Correct answer: A
Rationale: The items listed are early signs of a cholinergic crisis, which can become more severe and lead to hypotension, circulatory collapse, bloody diarrhea, shock, and cardiac arrest.
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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.)
Direct-acting drug—bethanechol
Increases tone and motility of bladder and gastrointestinal (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.)
Direct-acting drug—cevimeline
Used to treat excessively dry mouth (xerostomia) resulting from a disorder known as Sjögren’s syndrome
Direct-acting drug—succinylcholine
Used as a neuromuscular blocker in general anesthesia
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Indications (Cont.)
Indirect-acting drugs
Increase ACh concentrations at the receptor sites, which leads to stimulation of the effector cells
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.)
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.)
memantine (Namenda)
Not a cholinergic drug
Also used in the treatment of Alzheimer’s disease
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Contraindications
Known drug allergy
GI or genitourinary (GU) tract obstruction
Bradycardia
Defects in cardiac impulse conduction
Hyperthyroidism
Epilepsy
Hypotension
Chronic obstructive pulmonary disease
Parkinson’s disease
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Adverse Effects
Adverse effects are a result of overstimulation of the PSNS
Cardiovascular
Bradycardia, hypotension, syncope, conduction abnormalities (AV block and cardiac arrest)
Central nervous system
Headache, dizziness, convulsions, ataxia
Gastrointestinal
Abdominal cramps, increased secretions, nausea, vomiting
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24. Adverse Effects (Cont.)
Respiratory
Increased bronchial secretions, bronchospasms
Other
Lacrimation, sweating, salivation, miosis
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Cholinergic Crisis
Circulatory collapse, hypotension, bloody diarrhea, shock, and cardiac arrest.
SLUDGE, which stands for salivation, lacrimation, urinary incontinence, diarrhea, GI cramps, and emesis
Early signs
Abdominal cramps, salivation, flushing of the skin, nausea, and vomiting, transient syncope, transient complete heart block, dyspnea, and orthostatic hypotension
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26. Cholinergic Crisis (Cont.)
Treatment in early phase: atropine, a cholinergic antagonist
Treatment of severe cardiovascular reactions or bronchoconstriction: epinephrine, an adrenergic agonist
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Interactions
Anticholinergics, antihistamines, sympathomimetics
Antagonize cholinergic drugs, resulting in decreased responses
Other cholinergic drugs
Additive effects
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28. Bethanechol (Urecholine)
Direct-acting cholinergic agonist
Uses: treatment of acute postoperative and postpartum nonobstructive urinary retention and for the management of urinary retention associated with neurogenic atony of the bladder
Contraindications: known drug allergy, hyperthyroidism, peptic ulcer, active bronchial asthma, cardiac disease or coronary artery disease, epilepsy, and parkinsonism
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29. Bethanechol (Urecholine) (Cont.)
Adverse effects: syncope, hypotension with reflex tachycardia, headache, seizure, GI upset, and asthma attacks
Interactions: acetylcholinesterase inhibitors (i.e., indirect-acting cholinergics)
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Donepezil (Aricept)
Cholinesterase inhibitor that works centrally in the brain to increase levels of ACh by inhibiting acetylcholinesterase
Used in the treatment of mild to moderate Alzheimer’s disease
Similar cholinesterase inhibitors include galantamine and rivastigmine.
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31. Donepezil (Aricept) (Cont.)
Contraindications: known drug allergy
Adverse effects: GI upset (including ulcer risk caused by increased gastric secretions), drowsiness, dizziness, insomnia, and muscle cramps. The effects on the cardiovascular system are complex and may include bradycardia, syncope, hypotension with reflex tachycardia, or hypertension.
Interacting drugs: anticholinergics (counteract donepezil effects) and nonsteroidal antiinflammatory drugs (NSAIDs)
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32. Pyridostigmine (Mestinon)
Indirect-acting cholinergic drugs that work to increase ACh by inhibiting acetylcholinesterase
Use: myasthenia gravis
Edrophonium (Tensilon): indirect-acting cholinergic drug that is used to diagnose myasthenia gravis. It can also be used to differentiate between myasthenia gravis and cholinergic crisis.
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33. Neostigmine, Pyridostigmine, and Physostigmine
Uses: reversing the effects of nondepolarizing neuromuscular blocking drugs; treating severe overdoses of tricyclic antidepressants; and antidote after toxic exposure to nondrug anticholinergic agents, including those used in chemical warfare
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34. 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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35. Audience Response System 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?
Stomach upset
Diarrhea
Bleeding
Drowsiness
Correct answer: C
Rationale: Potential adverse effects of gingko include stomach or intestinal upset, headache, bleeding, and allergic skin reaction. Potential drug interactions include aspirin, NSAIDs, anticoagulants, and other drugs. The ginkgo may interact with the NSAID medication and cause increased bleeding.
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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, and coronary artery disease.
Perform baseline assessment of vital signs and systems overview.
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37. Nursing Implications (Cont.)
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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38. Audience Response System Question
A patient is scheduled to have lunch at The nurse will administer the pyridostigmine (Mestinon) at what time for optimal therapeutic effect?
1100
1130
1200
1230
Correct answer: B
Rationale: The drug should be taken 30 minutes before a meal for maximal therapeutic effect.
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39. Nursing Implications (Cont.)
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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40. Audience Response System 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?
Administration of physostigmine
Administration of atropine
Administration of epinephrine
Cardiovascular support with dopamine
Correct answer: B
Rationale: Atropine can be given to reverse the effects of an overdose of a cholinergic drug.
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41. Nursing Implications (Cont.)
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 physicians if they experience muscle weakness, abdominal cramps, diarrhea, or difficulty breathing.
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42. Nursing Implications (Cont.)
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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43. Nursing Implications (Cont.)
Monitor for therapeutic effects
In patients with urinary retention or 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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