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.

1. Anticholinergics

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.

4. Classification

Natural:
Atropine,
Hyoscine (Scopolamine)

Semisynthetic:
Homatropine
Atropine methonitrate
Ipratropium bromide
Hyoscine butylbromide

5. 
Synthetic:
a)
Mydriatics: Cyclopentonate, Tropicamide
b) Antisecretory antispasmodic:
I) Quaternary compounds:
Propantheline, Clidinium, Oxyphenonium,
Pipenzolate methyl bromide, Glycopyrolate.
II) Tertiary compounds: Dicyclomine, Pirenzepine
c) Vasicoselective: Oxybutinin, Flavoxate, Tolterodine
d) Antiparkinsonian: Trihexyphenidyl, Biperidin.

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

9. Atropine substitutes
Quaternary compounds
 Hyoscine butyl bromide- 20-40mg oral, i.m.,
Use- oesophageal, Gi spastic conditions.

Atropine methonitrate-2.5-10mg orally, im
Use-abdominal colic, hyperacidity

Ipratropium bromide-40-80microgram inhalational
Use-COPD, Bronchial asthma

10. Quaternary compounds

Glycopyrrolate: 0.1-0.3 mg im,1-2 mg oral
No central effect
 Potent and rapidly acting antimuscarinic
 Use- For preanaesthetic medication and during
anaesthesia


Propanthelin, Clidinium, OxyphenoniumUse- peptic ulcer , gastritis, irritable bowel
syndrome, colic, gi hypermotility

11. Tertiary amines

Dicyclomine :20mg oral/im
Direct smooth muscle relaxant action
 Antispasmodic action
 Antiemetic
 Use: Dysmenorrhea, irritable bowel syndrome,
motion sickness, morning sickness.


Pirenzepine :Use-relief of peptic ulcer pain

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

14. Uses

As antisecretory
Preanaesthetic medication-(Atropine, glycopyrolate, hyosine)
 Peptic ulcers
 Pulmonary embolism
 To check sweating , salivation in parkinsonism


As antispasmodic
Intestinal, biliary, renal colic, abdominal cramps
 Nervous , functional diarrheoa
 Irritable bowel syndrome, spastic constpation
 Pylorospasm, gastric hypermotility, gastritis, gastric dyspepsia
 Urinary frequency, urgency, enuresis in children
 dysmenorrhea


15. 

Bronchial asthma, COPD
As mydriatic and cycloplegic



As cardiac vagolytic



Diagnostic
therapeutic
In partial AV block
AMI, digitalis toxicity
For central action



Motion sickness
Antiparkinsonian
OPPs

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

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