Anticholinergics, also known as cholinergic blocking agents, work by blocking the actions of acetylcholine in the parasympathetic nervous system. They are competitive antagonists that bind to muscarinic receptors, preventing acetylcholine from causing effects. Common uses include treating Parkinson's disease, asthma, peptic ulcers, and urinary incontinence. Side effects include increased heart rate, dilated pupils, dry mouth, constipation, difficulty urinating, and cognitive changes like confusion.
2. Anticholinergics
Drugs that block or inhibit the actions of
acetylcholine (ACh) in the parasympathetic nervous
system (PSNS) i.e. on muscarinic receptors:
Autonomic effectors
CNS
Nicotinic antagonists also block certain actions of
Ach, they are generally referred to as- Ganglionic
blockers / NMBs
3. Cholinergic Blocking Agents:
Mechanism of Action
Competitive antagonists
Compete 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. Pharmacological actions
Atropine as prototype
CNS
Overall CNS stimulant effect
Small doses: These effects are not appericiable,
decrease muscle rigidity and tremors
Large doses: stimulates medullary centres- vagal ,
respiratory, vasomotor centres
drowsiness, disorientation, hallucinations –(cortical
excitation)
Depresses vestibular excitation- antimotion sickness
property.
7.
Cardiovascular
Small doses: decrease heart rate
Large doses: increase heart rate, facilitates AV
conduction.
No considerable effect on BP
Eye
Dilated pupils (mydriasis)
Decreased accommodation due to paralysis
of ciliary muscles (cycloplegia lasting for 7-10 days)
This results into long lasting blurring of vision and
photophobia
Body temperature
Rise in body temp.high doses
Local anaesthetic
8.
Gastrointestinal
Relax smooth muscle tone of GI tract
Decrease intestinal and gastric secretions
Decrease motility and peristalsis
Genitourinary
Increased constriction of internal sphincter
Relaxed detrusor muscle
Result: urinary retention
Glandular
Decreased bronchial secretions, salivation, sweating
Respiratory
Decreased bronchial secretions
Dilated bronchial airways
12. Vasicoselective drugs
Oxybutinin
High affinity for receptors of urinary bladder, and
salivary glands
Uses : Neurogenic bladder
spina bifida
nocturnal enuresis
overactive bladder-urinary urgency,
frequency, dysuria
13.
Atropine
Potent
Slow & Longer acting
Undesirable for refraction tesing
10 times less potent than atropine
Dilatation takes 45-60mins last for 1-3 days
Cyclopentonate
Pupils dilates in 30-40mins,cycloplegia in 1-3 hrs last for a week
Homatropine
Mydriatics
Potent and fast acting (dilatation 30-60mins and last for 1day)
Preffered for cycloplegic refraction, uveitis, iritis
Adverse effects-transient behavioral abnormalities
Tropicamide
Quickest (onset-20-40mins , brief duration for 3-6 hrs)
Satisfactory for refraction testing in adults and for fundoscopy
17. 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
18. 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)
19. 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
20. Cholinergic Blocking Agents:
Therapeutic Uses
Respiratory agents are used to treat:
Exercise-induced bronchospasms
Chronic bronchitis
Asthma
Chronic obstructive pulmonary disease
21. 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
22. Cholinergic Blocking Agents:
Therapeutic Uses
Gastrointestinal agents are used to treat:
Peptic ulcer disease
Irritable bowel disease
GI hypersecretory states
23. Cholinergic Blocking Agents:
Therapeutic Uses
Genitourinary
Relaxed detrusor muscles of the bladder
Increased constriction of the internal sphincter
Reflex neurogenic bladder
Incontinence
24. Cholinergic Blocking Agents:
Side Effects
Body System
Side/Adverse Effects
Cardiovascular
Increased heart rate,
dysrhythmias
CNS
CNS excitation, restlessness,
irritability, disorientation,
hallucinations, delirium
25. 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
26. Cholinergic Blocking Agents:
Side Effects
Body System
Side/Adverse Effects
Genitourinary
Urinary retention
Glandular
Decreased sweating
Respiratory
Decreased bronchial secretions