This document discusses cholinergic blocking agents, which are drugs that block the actions of acetylcholine in the parasympathetic nervous system. It describes their uses in treating conditions like asthma, Parkinson's disease, and peptic ulcers. The document outlines the agents' mechanisms of action as competitive antagonists that bind to muscarinic receptors. It also details their therapeutic effects on organ systems and potential side effects like increased heart rate, urinary retention, and decreased secretions. Drug interactions that can cause additive cholinergic effects are also noted.

1. Cholinergic Antagonist
Agents
By: Dr. Sara Sam
Yuzuncu Yil University
2015

2. Cholinergic Blocking Agents: Chemical
Class
Natural Synthetic/Semisynthetic
atropine anisotropine clidinium
belladonna dicyclomine glycopyrrolate
hyoscyamine hexocyclium homatropine
scopolamine ipratropium isopropamide
oxybutynin propantheline
tolterodine tridihexethyl

3. Cholinergic Blocking Agents
• Drugs that block or inhibit the actions of
acetylcholine (ACh) in the parasympathetic
nervous system (PSNS)

4. USES:
• As miotic
• Myasthenia gravis
• Postoperative paralytic ileus/urinary retention
• Postoperative decurarization
• Cobra bite
• Belladona poisoning
• Alzheimer’s diseases
• Other drug overdosages

5. Cholinergic Blocking Agents:
Mechanism of Action
• Competitive antagonists
• Complete with ACh
• Block ACh at the muscarinic receptors
in the PSNS
– As a result, ACh is unable to bind to the
receptor site and cause a cholinergic effect.

6. Cholinergic Blocking Agents:
Mechanism of Action
Once these drugs bind to receptors, they inhibit
nerve transmission at these receptors.

7. Drug Effects of
Cholinergic Blocking Agents
• Cardiovascular
– Small doses: decrease heart rate
– Large doses: increase heart rate
• CNS
– Small doses: decrease muscle rigidity
and tremors
– Large doses: drowsiness, disorientation,
hallucinations

8. Drug Effects of
Cholinergic Blocking Agents
• Eye
– Dilated pupils (mydriasis)
– Decreased accommodation due to paralysis
of ciliary muscles (cycloplegia)
• Gastrointestinal
– Relax smooth muscle tone of GI tract
– Decrease intestinal and gastric secretions
– Decrease motility and peristalsis

9. Drug Effects of
Cholinergic Blocking Agents
• Genitourinary
– Relaxed detrusor muscle
– Increased constriction of internal sphincter
– Result: urinary retention
• Glandular
– Decreased bronchial secretions, salivation,
sweating
• Respiratory
– Decreased bronchial secretions
– Dilated bronchial airways

10. Cholinergic Blocking Agents:
Therapeutic Uses
CNS
Decreased muscle rigidity and muscle
tremors
• Parkinson’s disease
• Drug-induced extrapyramidal reactions

11. Cholinergic Blocking Agents:
Therapeutic Uses
Cardiovascular
Affect the heart’s conduction system
• Low doses: slow the heart rate
• High doses: block inhibitory vagal effects on
the SA and AV node pacemaker cells
– Result: increased heart rate

12. Cholinergic Blocking Agents:
Therapeutic Uses
Atropine
Used primarily for cardiovascular disorders
• Sinus node dysfunction
• Symptomatic second-degree heart block
• Sinus bradycardia with hemodynamic compromise
(advanced life support)

13. Cholinergic Blocking Agents:
Therapeutic Uses
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. Cholinergic Blocking Agents:
Therapeutic Uses
Respiratory agents are used to treat:
• Exercise-induced bronchospasms
• Chronic bronchitis
• Asthma
• Chronic obstructive pulmonary disease

15. Cholinergic Blocking Agents:
Therapeutic Uses
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

18. Cholinergic Blocking Agents:
Therapeutic Uses
Gastrointestinal agents are used to treat:
• Peptic ulcer disease
• Irritable bowel disease
• GI hypersecretory states

19. Cholinergic Blocking Agents:
Therapeutic Uses
Genitourinary
• Relaxed detrusor muscles of the bladder
• Increased constriction of the internal
sphincter
• Reflex neurogenic bladder
• Incontinence

20. Cholinergic Blocking Agents:
Side Effects
Body System Side/Adverse Effects
Cardiovascular Increased heart rate,
dysrhythmias
CNS CNS excitation, restlessness,
irritability, disorientation,
hallucinations, delirium

21. Cholinergic Blocking Agents:
Side Effects
Body System Side/Adverse Effects
Eye Dilated pupils, decreased visual
accommodation, increased intraocular
pressure
Gastrointestinal Decreased salivation,
decreased gastric secretions,
decreased motility

22. Cholinergic Blocking Agents:
Side Effects
Body System Side/Adverse Effects
Genitourinary Urinary retention
Glandular Decreased sweating
Respiratory Decreased bronchial secretions

23. Cholinergic Blocking Agents:
Interactions
• Antihistamines, phenothiazines,
tricyclic antidepressants, MAOIs
• When given with cholinergic blocking
agents, cause ADDITIVE cholinergic
effects, resulting in increased effects