Cholinergic Agonists
Drug Actions Receptor Therapeutic Effects Pharmacokinetics Adverse Effects Others
Acetylcholine -decreases heart rate and cardiac - acts on -no importance -actions are rapidly -Quaternary
(Direct) output both therapeutically inactivated by Ach- ammonium
-decrease in BP by activating M3 muscarinic -Ach (1 % soln) instilled into esterase compound
receptors on SM of BV and nicotinic anterior chamber of eye to -ATROPINE blocks M
-Increases salivary secretion and receptors produce miosis during receptors and
stimulates intestinal secretions and ophthalmic surgery prevents Ach from
motility producing
-Bronchiolar secretions are vasodilatation
enhanced
-Stimulates ciliary muscles to
contract for near vision and
pupillary muscles to constrict,
causing miosis
Bethanechol -Acts on the smooth muscles of -Lacks -Used to stimulate atonic -Duration of action -Sweating -Inactivated through
(Direct) bladder and GIT nicotinic bladder (postpartum, of 1 hour -Salivation hydrolysis by
-Increased intestinal motility and action postoperative, -Flushing esterases
tone -Strong nonobstructive urinary -Decreased BP -Ester of carbamic
-Expulsion of urine by stimulating muscarinic retention) -Nausea acid
detrusor muscle activity -Neurogenic atony -Abdominal pain
-Megacolon -Diarrhea
-Bronchospasm
Carbachol -Ganglion-stimulating activity -Both -Rarely used therapeutically -Single -Uses in the eye cause -Ester of carbamic
(Direct) effects CVS and GIT; first stimulates muscarinic -Used as a miotic agent in administration can little or no side effects acid
and then depresses these systems and nicotinic the eye to treat glaucoma last up to 1 hour -Biotransformed by
-Nicotinic action causes release of activity esterases at slow rate
epinephrine from adrenal medulla
-Causes miosis and spasm of
accommodation (ciliary muscles are
in constant state of contraction)
Pilocarpine -Topical application to cornea -Muscarinic -Sjogren’s syndrome -Actions last up to -CNS disturbances -Tertiary amine
(Direct) produces rapid miosis and activity (pilocarpine + CEVIMELINE) 8 hours -Stimulates profuse -Can be hydrolyzed by
contraction of ciliary muscles -DOC in emergency cases of sweating and Ach-esterase
-Stimulates secretions (saliva, narrow-angle and wide- salivation -Uncharged, so can
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Cholinergic Agonists
sweat, tears) angle glaucoma penetrate CNS
-ECHOTHIOPHATE
inhibits Ach-esterase
and causes longer
duration action of the
drug
Physostigmine -can enter the CNS and stimulate -Nicotinic -Increases intestinal and -Duration of action -High doses: -Nitrogenous
(Indirect) cholinergic sites and bladder motility is 2-4 hours convulsions carbamic acid ester
-Substrate for Ach-esterase, after muscarinic -Topically in the eye it -Bradycardia, fall in CO -Tertiary amine
binding to it, it causes the enzyme receptors produces miosis and spasm -Paralysis of skeletal
to become reversibly inactive of accommodation muscles due to
-Lowers IOP, so used to treat inhibition of Ach-
glaucoma esterase
-Used in treatment of
overdoses of drugs with
anticholinergic actions
(ATROPINE, TRICYCLIC
ANTIDEPRESSANTS, PHENO-
THIAZINES)
Neostigmine -reversibly inhibits Ach-esterase -Used to stimulate bladder -Duration of action -Salivation -Synthetic carbamic
(Indirect) -has a great effect on skeletal and GIT is 30 minutes to 2 -Flushing acid ester
muscles, so it can stimulate -Antidote for hours -Decreased BP -Quaternary nitrogen,
contractility before it paralyzes TUBOCURARINE and other -Nausea therefore more polar
competitive NM blocking -Abdominal pain and can’t enter CNS
agents -Diarrhea
-Symptomatic treatment of -Bronchospasm
myasthenia gravis
Pyridostigmine -Used in the management of -Pyridostigmine: 3- -Salivation
and myasthenia gravis 6 hours -Flushing
Ambenomium -Ambenomium: 4-8 -Decreased BP
(Indirect) hours -Nausea
-Abdominal pain
-Diarrhea
-Bronchospasm
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Cholinergic Agonists
Demecarium -Actions similar to NEOSTIGMINE -Used to treat chronic open- -Salivation -Quaternary amine
(Indirect) angle glaucoma and closed- -Flushing that is structurally
angle glaucoma after -Decreased BP related to
irredectomy -Nausea NEOSTIGMINE
-Diagnosis and treatment of -Abdominal pain
accommodative esotropia -Diarrhea
(strabismus) -Bronchospasm
Edrophonium -Similar to NEOSTIGMINE, but is -Diagnosis of myasthenia -Duration of action -Excess drug causes -Quaternary amine
(Indirect) more rapidly absorbed gravis is 10-20 minutes cholinergic crisis -Antidote: ATROPINE
- IV injection leads
to rapid increase in
muscle strength
Tacrine - Donepezil, Galantamine, -used in the treatment of -First line of drugs: -Tacrine: -Tacrine was the first
Donepezil Rivastigmine delay the progression Alzheimer’s disease Donepezil, hepatotoxicity one to become
Rivastigmine of the disease but can’t stop it Galantamine, -First line of drugs available
Galantamine Rivastigmine cause GI distress
Echothiophate -Binds via its P-group to the serine- -Treatment of open-angle -Effect on -Cataracts -Organophosphate
(Indirect, OH group at the active site of Ach- glaucoma glaucoma can last -ATROPINE can
Irreversible) esterase, permanently inactivating - up to one week reverse the
it after single muscarinic and
-After covalent modification of Ach- administration central effects of the
esterase, the enzyme slowly drug
releases one of its ethyl groups -PRALIDOXIME can
(aging) reactivate inhibited
-Paralysis of motor function, Ach-esterase; if given
convulsions before aging of the
alkylated enzyme it
can reverse the
effects of the drug,
except those in the
CNS
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