1. CHAPTER 21 Cholinergic-Blocking Drugs
Mosby items and derived items © 2011, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

2. Definition
Drugs that block or inhibit the actions of acetylcholine (ACh) in the parasympathetic nervous system (PSNS)
Also known as anticholinergics

3. Mechanism of Action Competitive antagonists Compete with ACh
Block ACh 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

5. Chemical Class Natural Synthetic/Semisynthetic
atropine benztropine clidinium
belladonna dicyclomine glycopyrrolate
hyoscyamine homatropine ipratropium
scopolamine isopropamide methscopolamine
oxybutynin propantheline
tolterodine trihexyphenidyl
Many Others

6. Drug Effects Cardiovascular CNS Small doses: decrease heart rate
Large doses: increase heart rate
CNS
Small doses: decrease muscle rigidity and tremors
Large doses: drowsiness, disorientation, hallucinations

7. Drug Effects (cont’d) Eye Gastrointestinal 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

8. Drug Effects (cont’d) Genitourinary Glandular Relaxed detrusor muscle
Increased constriction of internal sphincter
Result: urinary retention
Glandular
Decreased bronchial secretions, salivation, sweating

9. Drug Effects (cont’d) Respiratory Decreased bronchial secretions
Dilated bronchial airways

10. Indications: CNS Decreased muscle rigidity and muscle tremors
Parkinson’s disease
Drug-induced extrapyramidal reactions

11. Indications: Cardiovascular
Affect the heart’s conduction system
Low doses: slow the heart rate
High doses: block inhibitory vagal effects on SA and AV node pacemaker cells
Results in increased heart rate

12. 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)

13. 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

14. Indications: Respiratory (cont’d)
Respiratory drugs are used to treat:
Exercise-induced bronchospasms
Chronic bronchitis
Asthma
Chronic obstructive pulmonary disease

15. 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

16. Indications: Gastrointestinal (cont’d)
Gastrointestinal drugs are used to treat:
Irritable bowel disease
GI hypersecretory states

17. Indications: Genitourinary
Reflex neurogenic bladder
Incontinence

18. Indications
Acute pancreatitis: reduces gastric and pancreatic secretions
Preoperatively: reduces salivary secretions

19. Adverse Effects Body System Adverse Effects
Cardiovascular Increased heart rate, dysrhythmias
CNS CNS excitation, restlessness, irritability, disorientation, hallucinations, delirium

20. Adverse Effects (cont’d)
Body System Adverse Effects
Eye Dilated pupils, decreased visual accommodation, increased intraocular pressure
Gastrointestinal Decreased salivation, decreased gastric secretions, decreased motility

21. Adverse Effects (cont’d)
Body System Adverse Effects
Genitourinary Urinary retention
Glandular Decreased sweating
Respiratory Decreased bronchial secretions

22. Interactions
Antihistamines, phenothiazines, tricyclic antidepressants, MAOIs
When given with cholinergic blocking drugs, cause additive cholinergic effects, resulting in increased effects

23. Nursing Implications
Keep in mind that these drugs block the action of ACh in the PSNS
Assess for allergies, presence of BPH, glaucoma, tachycardia, MI, HF, hiatal hernia, and GI or GU obstruction
Perform baseline assessment of vital signs and systems overview

24. 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 may cause problems with driving or operating machinery

25. 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

26. 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

27. 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

28. Nursing Implications (cont’d)
Patients should report the following symptoms to their physician: urinary hesitancy and/or retention, constipation, palpitations, tremors, confusion, sedation or amnesia, excessive dry mouth (especially if they have chronic lung infections or disease), or fever

29. 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