4.cholinergic and anticholinergics

cholinergics

1. Drugs Acting On Autonomic Drugs Acting On Autonomic
Nervous System (ANS)Nervous System (ANS)

3. Neurotransmitters Neurotransmitters
Sympathetic: noradrenaline
(norepinephrine)
Parasympathetic : acetylcholine

5. Cholinergic receptorsCholinergic receptors
 Muscarinic: M
1
– M
5
Activated by muscarine
 Nicotinic: N
M
, N
N

Activated by nicotine

6. Actions of AchActions of Ach
Acetylcholine – major neurotransmitter
of PNS

7. Actions of Ach
CharacteristicsM
1

(neuronal)
M
2
(cardiac)
M
3

(glandular)
Location &
Function
• Ganglia –
impulse
transmission
• SA node
-Decreased rate
of impulse
generation
• AV node –
decreased
conduction
velocity
• Atrium,
ventricle-
decreased
contractility
• Exocrine
glands-
secretion
• Visceral
smooth Muscle
– contraction

8. Actions of Ach
CharacteristicsM
1

(neuronal)
M
2
(cardiac)
M
3

(glandular)
Location &
Function
• Ganglia –
impulse
transmission
• SA node
-Decreased rate
of impulse
generation
• AV node –
decreased
conduction
velocity
• Atrium,
ventricle-
decreased
contractility
• Exocrine
glands-
secretion
• Visceral
smooth Muscle
– contraction

9. Actions of Ach
CharacteristicsM
1

(neuronal)
M
2
(cardiac)
M
3

(glandular)
Location &
Function
• Ganglia –
impulse
transmission
• SA node
-Decreased rate
of impulse
generation
• AV node –
decreased
conduction
velocity
• Atrium,
ventricle-
decreased
contractility
• Exocrine
glands-
secretion
• Visceral
smooth Muscle
– contraction

10. Actions of Ach
CharacteristicsM
1

(neuronal)
M
2
(cardiac)
M
3

(glandular)
Location &
Function
• Ganglia –
impulse
transmission
• SA node
-Decreased rate
of impulse
generation
• AV node –
decreased
conduction
velocity
• Atrium,
ventricle-
decreased
contractility
• Exocrine
glands (salivary,
sweat)
-secretion
• Visceral
smooth Muscle
(bronchus,
bladder, GIT) –
contraction

11. Actions of Ach
Characteristics N
M
(muscle type)
N
N
(neuronal type)
Location &

Function
Skeletal
neuromuscular
junction (NMJ) –
contraction
• Autonomic
ganglia– impulse
transmission

12. Actions of ACh on eye
Muscarinic:
Eye:
-Circular muscle of iris (M
3
)- contraction-
miosis
-Ciliary muscle (M
3
) – contraction- eye’s
focus is accomodated for near vision –
spasm of accomodation
-Better drainage of aqueous humor – reduced
intraocular pressure
-Lacrimal glands (M
3
) - lacrimation

13. Acetylcholine Acetylcholine
No therapeutic use because
i)Ultra short action: rapidly
hydrolyzed by cholinesterases
ii)Widespread and nonselective
activity: act on all receptors

14. Drugs which mimic the actions of
Ach are called as cholinergic drugs
or parasympathomimetic drugs or
cholinomimetic or cholinergic
agonists

15. Classification
1. Directly acting
Methacholine, bethanechol, pilocarpine

Act on muscarinic receptors

16. 2. Indirectly acting (Anticholinesterases)
A. Reversible :
Physostigmine, neostigmine,
pyridostigmine, edrophonium
B. Irreversible:
Organophosphates: Parathion, Malathion

17. Mechanism of action of
Anticholinesterases
Inhibit acetylcholinesterase (AChE) enzyme
Ach ----------- Choline + acetate
AChE
Accumulation of Ach  Action

Neostigmine
___
_

18. Therapeutic uses
Ophthalmic use :
i) Glaucoma
ii)To counteract the effects of mydriatics
iii) To break adhesions between the iris and
lens or iris and cornea
Myasthenia gravis : neostigmine
Belladona (Atropine) poisoning :
Physostigmine – specific antidote

19. Irreversible AChE inhibitorsIrreversible AChE inhibitors
Mainly used as insecticides and
pesticides

20. Adverse effects of Adverse effects of
anticholinesterases anticholinesterases
Diarrhea, urination, bronchoconstriction,
lacrimation, salivation, sweating,
bradycardia, fasciculation of skeletal
muscle
Organophosphorus poisoning: treated
with an anticholinergic, atropine

21. Anticholinergic DrugsAnticholinergic Drugs

22. Classification
Natural alkaloids :
Atropine* (prototype), Scopolamine
(Hyoscine)
Semisynthetic derivatives :
Homatropine*, ipratropium bromide,
tiotropium bromide
Synthetic compounds :
i)Mydriatics – Cyclopentolate*, tropicamide
ii)Antiparkinsonian – Benzhexol, Biperiden,
Benztropine

23. iii) Antisecretory- antispasmodics –
Dicyclomine
Pirenzepine
Glycopyrrolate
Semisynthetic and synthetic anticholinergics
- Atropine substitutes

24. Pharmacological actions of atropinePharmacological actions of atropine
CNS :
High doses – restlessness, delirium,
disorientation

25. CVS :
Tachycardia

26. Eye :
mydriasis : “Passive mydriasis”
Photophobia, abolition of light reflex
“Paralysis of accomodation or cycloplegia”
Rise in IOP
Decrease in lacrimation – dry eyes

27. Respiratory system :
Bronchodilatation
Decreased secretions
GIT :
Reduce gastric acid secretion
Reduced tone and motility of gut, constriction
of sphincters – constipation

28. Genitourinary tract :
Relaxation of ureter and urinary bladder –
urinary retention
Glands :
Decreases sweat, salivary, tracheobronchial
and lacrimal secretion
Body temperature :
Rise in body temperature
“Atropine fever”

29. Uses of atropine Uses of atropine
Preanaesthetic medication: to decrease
secretion
Oraganophosphorous poisoning

30. Therapeutic uses Therapeutic uses
Motion sickness : Scopolamine
Parkinson’s disease :benzhexol,
benztropine etc.
Bronchial asthma : ipratropium and
tiotropium bromide
Preanaesthetic medication :
glycopyrrolate ,
As mydriatic during fundoscopy and
testing of refractive error – Tropicamide,
cyclopentolate

31. Side effects of atropine :
Dry mouth
Blurred vision and photophobia
Urinary retention
Constipation
Dry, hot skin
Precipitation of glaucoma
Decreased sweating