Drugs that are similar to ACh and acts in the body as normal neurotransmitter does

1. Prepared by: Anish Dhakal (Aryan)
MBBS Student
Patan Academy of Health Sciences

2. OBJECTIVES
• Define cholinergic drugs
• Classification of the cholinergic agonist
• Cholinergic agonist and their mechanism
of action, indication, contraindication,
adverse effects
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3. CHOLINERGIC DRUG
• Those drugs that act on receptors
activated by acetylcholine
• They are of two types
- Cholinergic agonist
- Cholinergic antagonist
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4. CHOLINERGIC
AGONIST
1. Direct
- By direct interaction with
cholinergic receptors
( cholinomimetics )
2. Indirect
- By increasing availability of
Ach at these sites ( anti
cholinesterases )
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5. ACETYLCHOLINE
• Therapeutic importance is absent(non
specific & rapid degradation)
• Actions:
Decreases heart rate and blood pressure
Increases gastric secretions and motility
Expulsion of urine & Miosis
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6. Bethanechol
• Resists hydrolysis by AChE
• Strong muscarinic activity and lacks
nicotinic activity
• Major actions on the smooth muscles
Uses:
To stimulate the atonic bladder (Post
partum, post operative and non
obstructive urinary retention)
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7. Bethanechol
• Adverse effect :
Sweating, salivation
Flushing
Decreased B.P
Nausea, abdominal pain, diarrhea,
Bronchospasm
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8. Carbachol
• Ester of carbamic acid
• Both Muscarinic and Nicotinic
actions
• Act on CVS and GIT
• Uses:
Miotic agent to treat glaucoma
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9. PILOCARPINE
• It has Muscarinic action
• Penetrate CNS at low doses
• Uses:
 Glaucoma
 Xerostomia
• Adverse Effects:
 Cause CNS disturbances
 Profuse sweating and salivation
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10. ANTICHOLINESTERASES
• Enzyme that specifically cleaves
acetylcholine to acetate and choline and
terminates its action
• They are of two types
1. Reversible inhibitors
2. Irreversible inhibitors
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12. PHYSOSTIGMINE
• Substrate for Ach esterases
• Both muscarinic and nicotinic action
• Duration of action is 2 to 4 hours
• Can enter CNS
• Uses :
 Glaucoma
 Over doses of anticholinergic drugs
 Atony of intestine and bladder
• Adverse effect:
Convulsions, bradycardia, paralysis
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13. NEOSTIGMINE
• Similar to Physostigmine but doesn’t enters CNS
• Duration of action is 30 minute to 2 hrs.
• Best at Neuromuscular junction than Physostigmine
• Uses:
 Antidote for tubocuranine
 Myasthenia gravis
 Stimulate bowel and bladder
• Adverse Effects:
 Generalized cholinergic stimulation ( salivation,
flushing, nausea, diarrhea , bronchospasm)
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14. PYRIDOSTIGMINE
• Resembles Neostigmine in all respect but
less potent , longer acting , less frequent
dosing
Use:
Chronic management of Myasthenia gravis
Adverse effect:
Similar to Neostigmine
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15. Edrophonium
• Duration of action 10 to 20 minutes
• Use:
Tensilon test
• Adverse effect:
 Excessive drug may cause cholinergic
crisis for which the antidote is Atropine
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16. Tacrine, Donepezil,
Rivastigmine and Galantamine
• Use in Alzheimer
• Tacrine was first available but because
of its hepatotoxicity was replaced by
others
• Adverse effect:
GI distress
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17. IRREVERSIBLE INHIBITOR
• Echothiophate
Via its phosphate group binds to Ach
esterase (Enzyme deactivated)
Phosphorylated enzyme releases alkyl
group ( Aging )
Antidote like Pralidoxime act before
aging
Produces miosis, used for Glaucoma
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18. Contraindications of
Cholinergic Agonists
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19. ADR of Cholinergic Agonists
• Diarrhea
• Diaphoresis
• Miosis
• Nausea
• Urine urgency
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