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1. ANTICHOLINERGIC DRUGS /
CHOLINERGIC ANTAGONIST
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Professor Dr. S. Mohsin Turab
Head, Department of Pharmacology
Hamdard College of Medicine Dentistry
Email: mturab68@gmail.com

2. 1.
2.
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b.
ANTI-MUSCARINIC
ANTI-NICOTINIC
Ganglion blockers
Neuromuscular Blockers

3. ANTI-MUSCARINIC AGENTS
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Those which blocks muscarinic receptors
Five sub divisions of receptors M1 to M5
M1 → nerves
M2 → heart
M3 → glands smooth muscles
M4 M5 → CNS

4. CLASSIFICATION
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2.
3.
a)
NATURAL ALKALOIDS
Atropine, Hyoscine (scopolamine)
SEMISYNTHETIC DERIVATIVES
Homatropine, Ipratropium bromide
SYNTHETIC COMPOUNDS
They are further classified according to their actions
MYDRIATICS
Cyclopentolate, Tropicamide

5. CLASSIFICATION
b)
c)
ANTISECRETORY-ANTISPASMODICS
Glycopyrolate, Oxyphenonium, Trospium
ANTIPARKINSONIAN
Benztropine , Orphenadrine, Biperiden

6. ATROPINE
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Prototype of this group
Blocks all subtypes of muscarinic receptor
PHARMACOKINETIC
Rapidly absorbed from GIT
50% of the drug metabolized in liver rest is excreted
unchanged in urine
Do not cross BBB
Plasma half life is 3-4 hours

7. MECHANISM OF ACTION
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Causes reversible blockade of cholinomimetic actions at
muscarinic receptors
On binding to receptors it prevents actions such as
Release of inositol triphosphate (IP3)
Inhibition of adenylyl cyclase
Highly selective for muscarinic receptors
Tissues most sensitive to atropine are
Salivary , bronchial sweat glands

8. SYSTEMIC EFFECTS
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CNS
Mainly excitatory
CVS
In moderate to high therapeutic doses causes
Tachycardia through block of cardiac muscarinic (M2)
receptors vagal slowing
Facilitates A-V conduction
In low doses results in initial bradycardia before the effect of
peripheral vagal block become manifest due to block of
prejunctional M1 receptors on vagal post ganglionic fibers
that normaly limit Ach release in the sinus node other
tissues

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EYE
Mydriasis due to unapposed effect of sympathetic dilator
activity on dilator pupillae
Abolition of light reflex cycloplegia due to blockage of ciliary
muscles
Photophobia blurring of vision
MUSCLES
Constipatory effect in GIT (M3)
Bronchodilation reduces airway resistance
Increases bladder capacitance slows voiding
GLANDS
Decreases secretions in salivary, lacrimal, bronchial sweat
glands
Also decreases gastric acid pepsin secretion

10. ATROPINE SUBSTITUTES
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Incomplete oral absorption
Do not cross BBB
Hyoscine butylebromide is less potent but longer acting
Ipratropium acts selectively on bronchial muscles, does not
depress mucociliary clearance
Oxyphenonium pipenzolate are used in GI colics
Glycopyrrolate, potent and rapidly acting antimuscarinic,
lacking central effects
Oxybutynin has high affinity for receptors in urinary bladder
(M3)
Pirenzepine selectively blocks M1 receptors, inhibits gastric
secretion
Benztropine Biperiden acts by blocking the relative
cholinergic overactivity in basal ganglia, suppresses tremors
rigidity

11. THERAPEUTIC APPLICATIONS
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Parkinson's disease
Vestibular disorders (Scopolamine)
Diagnostic for testing refractive errors fundoscopy
Bronchial asthma
Peptic ulcer
Anti-spasmodic
Anti-diarrheal
Urinary incontinence
Cholinergic poisoning
Hyperhidrosis (excessive sweating)

12. CHOLINERGIC POISONING
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Organophosphorus compound poisoning
Mushroom poisoning
Rapid onset (excess muscarinic activity)
Delayed onset, involves hepatic renal cellular injury by
amatoxins that inhibit RNA polymerase.
Ani-muscarinic therapy, to reverse the over activity of nicotinic
and muscarinic effects
Cholinesterase regenerator compounds
Pralidoxime 1-2 gm I/V over 15-30 min
Diacetylemonxime

13. SIDE EFFECTS TOXICITY
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Dry mouth
Blurred vision
Tachycardia
Constipation
Belladonna poisoning
Symptoms of anti-muscarinic over activity, hypotension, rapid
pulse, cardiovascular collapse, respiratory depression,
convulsions coma
Treatment : A) General measures
B) Physostigmine, 1-3mg S/C or I/V to antagonize
both central peripheral effects

14. CONTRAINDICATION
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Prostatic hypertrophy
Narrow angle glaucoma