1. Cholinergic-Blocking Drugs
Chapter 21
Cholinergic-Blocking Drugs
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2. Cholinergic-Blocking Drugs
Drugs that block or inhibit the actions of acetylcholine (ACh) in the parasympathetic nervous system (PSNS)
Also known as anticholinergics, parasympatholytics, and antimuscarinic drugs
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Mechanism of Action
Competitive antagonists
Compete with ACh for binding at muscarinic receptors in the PSNS
As a result, ACh is unable to bind to the receptor site and cause a cholinergic effect
Once these drugs bind to receptors, they inhibit nerve transmission at these receptors
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5. Cholinergic-Blocking Drugs: Examples
atropine
dicyclomine (Bentyl)
glycopyrrolate (Robinul)
oxybutynin (Ditropan)
scopolamine (Transderm-Scōp)
tolterodine (Detrol)
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Drug Effects
Cardiovascular
Small doses: decrease heart rate
Large doses: increase heart rate
CNS
Small doses: decrease muscle rigidity and tremors
Large doses: drowsiness, disorientation, hallucinations
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Drug Effects (cont’d)
Eye
Dilated pupils (mydriasis)
Decreased accommodation caused by paralysis of ciliary muscles (cycloplegia)
Gastrointestinal
Relax smooth muscle tone of GI tract
Decrease intestinal and gastric secretions
Decrease motility and peristalsis
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8. Classroom Response Question
Which finding would the nurse anticipate when assessing a patient with an atropine overdose?
Moist skin
Miosis
Bradycardia
Urinary retention
Correct answer: D
Rationale: Atropine overdose is manifested by flushing, dry skin and mucous membranes, mydriasis, altered mental status, and fever. Other serious effects include sinus tachycardia, urinary retention, hypertension, hallucinations, and cardiovascular collapse. Activated charcoal is usually given along with supportive therapy.
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Drug Effects (cont’d)
Genitourinary
Relaxed detrusor muscle
Increased constriction of internal sphincter
Result: urinary retention
Glandular
Decreased bronchial secretions, salivation, sweating
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Drug Effects (cont’d)
Respiratory
Decreased bronchial secretions
Dilated bronchial airways
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Indications: CNS
Decreasing muscle rigidity and muscle tremors
Parkinson’s disease
Drug-induced extrapyramidal reactions
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12. Indications: Cardiovascular
Affects the heart’s conduction system
Low doses: slow the heart rate
High doses: block inhibitory vagal effects on sinoatrial (SA) and atrioventricular (AV) node pacemaker cells
Results in increased heart rate
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13. Indications: Cardiovascular (cont’d)
Atropine
Used primarily for cardiovascular disorders
Diagnosis of sinus node dysfunction
Symptomatic second-degree heart block
Severe sinus bradycardia with hemodynamic compromise (advanced life support)
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14. Indications: 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
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15. Indications: Respiratory (cont’d)
Cholinergic blockers are used to treat:
Exercise-induced bronchospasms
Chronic bronchitis
Asthma
Chronic obstructive pulmonary disease
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16. Indications: 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
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17. Indications: Gastrointestinal (cont’d)
Gastrointestinal drugs are used to treat:
Irritable bowel disease
GI hypersecretory states
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18. Indications: Genitourinary
Reflex neurogenic bladder
Incontinence
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19. Classroom Response Question
Glycopyrrolate (Robinul) and an opioid are administered to a patient prior to surgery in the preoperative area. The anticholinergic is used to
potentiate the action of the opioid.
assist the patient in retaining urine during surgery.
control secretions during surgery.
prevent nausea.
Correct answer: C
Rationale: Anticholinergics such as glycopyrrolate and atropine are given preoperatively to reduce or control secretions before and during surgery.
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Indications
Acute pancreatitis: reduces gastric and pancreatic secretions
Preoperatively: reduces salivary secretions
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Adverse Effects
Body System
Adverse Effects
Cardiovascular CNS
Increased heart rate, dysrhythmias CNS excitation, restlessness, irritability, disorientation, hallucinations, delirium
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22. Adverse Effects (cont’d)
Body System
Adverse Effects
Eye Gastrointestinal
Dilated pupils (causing blurred vision), increased intraocular pressure Decreased salivation, decreased gastric secretions, decreased motility (causing constipation)
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23. Adverse Effects (cont’d)
Body System
Adverse Effects
Genitourinary Glandular Respiratory
Urinary retention Decreased sweating Decreased bronchial secretions
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24. Classroom Response Question
Prior to administering tolterodine (Detrol) it is most important for the nurse to assess the patient for a history of which condition?
Angle-closure glaucoma
Cataracts
Hypothyroidism
Hyponatremia
Correct answer: A
Rationale: Tolterodine (Detrol) may worsen pre-existing angle-closure glaucoma and urinary retention, so its use should be avoided in patients with these conditions.
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Interactions
Amantadine, antihistamines, phenothiazines, tricyclic antidepressants, digoxin
When given with other cholinergic blocking drugs, cause additive cholinergic effects, resulting in increased effects
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Nursing Implications
Keep in mind that these drugs block the action of ACh in the PSNS
Assess for allergies, presence of BPH, urinary retention, glaucoma, tachycardia, MI, HF, hiatal hernia, and GI or GU obstruction
Perform baseline assessment of vital signs and systems overview
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27. Nursing Implications (cont’d)
Medications should be taken exactly as prescribed to have the maximum therapeutic effect
Overdosing can cause life-threatening problems
Blurred vision will cause problems with driving or operating machinery
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28. Nursing Implications (cont’d)
Patients may experience sensitivity to light and may want to wear dark glasses or sunglasses
When giving ophthalmic solutions, apply pressure to the inner canthus to prevent systemic absorption
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29. Nursing Implications (cont’d)
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 over-the-counter medications
Antidote for atropine overdose is physostigmine
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30. Nursing Implications (cont’d)
Anticholinergics taken by the elderly patient may lead to higher risk for heatstroke because of the effects on heat-regulating mechanisms
Teach patients to limit physical exertion and avoid high temperatures and strenuous exercise
Emphasize the importance of adequate fluid and salt intake
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31. Nursing Implications (cont’d)
Patients should report the following symptoms to their physician: urinary hesitancy and/or retention, constipation, tachycardia, palpitations, tremors, confusion, sedation, hallucinations, decreased sweating (leading to hot, dry skin)
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32. Nursing Implications (cont’d)
Monitor for therapeutic effects
For patients with Parkinson’s disease: fewer tremors and decreased salivation and drooling
For patients with urologic problems: improved urinary patterns, less hypermotility, increased time between voiding
Monitor for adverse effects
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