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a.Therapeutic uses:
It is used as one percent eyedrops to produce miosis during eye surgeries.
Esters of choline are effective orally; carbol and bethanechol are resistant to both cholinesterases
and have a longer duration of action.Their muscarinic action are prominent with a sustained effect
on GI smooth muscles and urinary bladder.
Carbol is used in glaucoma.Bethamechol may be used in:
• Hypotonia of bladder.
• Hypotonia of GI smooth muscles.
• In some cases of postoperative paralytic ileus.
• Urinary retention.
• In xerostomia as an alternative to pilocarpine.
b.Route of administration:
Acetyl choline is destroyed in the gut when given orally.On intravenous administration, it is
rapidly metabolised by pseudocholinesterases in the plasma and by true cholinesterases at the site
of action.Therefore it is used only for intraocular (intracameral) administration.
c.Adverse effects:
Include diarrhoea, flushing , salivation, sweating, bradycardia, hypotension, syncope,and
bronchospasm.
d.Mechanism of action:
Acetylcholine is taken as the prototype of of parasympathomimetic drugs.
Muscarinic actions:These actions result from the stimulation of the muscarinic receptors by
acetylcholine.
• Heart: The action of Achis similar to that of vagal stimulation.It depresses SA node,reduces heart
rate and force of contraction.In larger doses, AV conduction is depressed.
• Blood vessels: Ach relaxes vascular smooth muscles,dilates blood vessels.
• Smooth muscles: Ach increases the tone of all other smooth muscles like GI tract,urinary
bladder,bronchial smooth muscles.
• Secretory glands:- Ach enhances secreation of all glands.Enhanced bronchial secretions and
bronchospasms result in severe dyspnea.
• Eye:- Ach brings about constriction of pupil(miosis) by contracting the circular muscles of the iris.
Nicotinic actions:These effects resemble the actions of the alkaloid nicotine and are brought about
by stimulation of the nicotinic receptors by acetylcholine.
• NMJ:- Ach brings about contraction of skeletal muscles by stimulating Nm receptors present in the
NMJ.
• Autonomic ganglia:-Ach stimulates the sympathetic and parasympathetic ganglia and the adrenal
medulla.
• CNS:- Ach is a neurotransmitter at several sites in the CNS.