Cholinergic Agonists Flashcards
Direct-acting Agonist
Bind to and activate Muscarinic or nicotinic receptors
Indirect-acting Agonist
Inhibit acetylcholinesterase
Direct effect of Acetylcholine
Vasodilation(M3 effect)
Decrease in cardiac rate(M2 effect)
Decrease in rate of conduction in the S.A and AV node (M2 effect)
Decrease in the force of contraction
What is the effect of Acetylcholine on Vasculature/endothelial cells?
Release of Nitric Oxide and vasodilation
Decrease in Blood pressure
What is the effect of Acetylcholine on Eye Iris?
Miosis- Constriction
What is the effect of Acetylcholine on Ciliary muscle?
accommodation of lens to near vision
What is the effect of Acetylcholine on Salivary/sweat/lacrimal glands?
inc in secretions
What is the effect of Acetylcholine on Bronchi?
constriction
What is the effect of Acetylcholine on heart?
Dec. Heart rate Dec conductance velocity
What is the effect of Acetylcholine on GI Tract?
Inc tonic and peristaltic activity
relaxation of sphincter
What is the effect of Acetylcholine on Urinary bladder?
Contraction of detrusor muscle
relaxation of sphincter
What are the two types of direct acting cholinergic Agonists?
Esters of choline and Alkaloids
What are the Choline esters
Acetylcholine
methacholine
Bethanecol
properties of Choline esters
Quaternary ammoniums
Poorly absorbed and distributed into the CNS
Acetylcholine is rapidly hydrolyzed
Methacholine and bethanecol more resistant to hydrolyzation
uses of Acetylcholine
Obtain miosis after delivery of the lens in cataract surgery and other procedures where rapid miosis is required
uses of Methacholine
Diagnosis of bronchial airway hyperactivity in subjects who do not have clinically apparent asthma
uses of Bethanecol
postoperative urinary retention
atony(lack of physiological tone especially of a contractile organ.) of the urinary bladder
What are the natural alkaloids
Pilocarpine and nicotine
Pilocarpine
Partial muscarinic agonist
Tertiary amine
stable to hydrolysis by acetylcholinesterase
uses of pilocarpine
Glaucoma
Treatment of dry mouth due to radio therapy for cancer of head and neck
Adverse effects of muscarinic agonists
sweating salivation flushing low blood pressure nausea abdominal pain diarrhea bronchospasm
Nicotine
tertiary amine
agonist at nicotinic receptors
depending on the doses can either be stimulating or cause paralysis
Nicotinic action at low doses
ganglionic stimulation via depolarization
Nicotinic action at high doses
ganglionic blockade and neuromuscular blockade
What are the anticholinesterases?
indirect acting cholinergic agents
Edrophonium -binds reversibly to the active site
carbamates- forms a covalent bond with the enzyme
organophosphates- phosphorylate enzyme and covalent bond formed is very stable
what is the mechanism of action for anticholinesterases?
inhibit cholinesterase.
increase in the concentration of endogenous acetylcholine
uses of Edrophonium
Diagnosis of myasthenia gravis
reverse the neuromuscular block produced by non-depolarizing muscular blockers
uses of Physostigmine
Treatment of overdoses of anticholinergic drugs
uses of neostigmine
urinary retention
cholinesterase inhibitor
reversal of effects of nondepolarizing neuromuscular blockers after surgery
Treatment of myasthenia gravis
uses of pyridostigmine
treatment of myasthenia gravis
Cholinesterase inhibitor
Malathion
used in pesticides/insecticides
Sarin
potent synthetic toxic agents
biowarfare bombs
Atropine
Reversible competitive antagonist at muscarinic receptors
Tertiary amine: both central and peripheral muscarinic blocker
Atropine action on : eye
Mydriases(dilation) and cycloplegia(focus on distant objects)
Atropine action on : GI
reduces gastric motility
Atropine action on : Urinary Tract
decreases hypermotility of urinary bladder (M3 Blockade)
Atropine action on : CV system
Atrial M2 Blockade- moderate to high therapeutic doses cause tachycardia
Atropine action on : Secretion
M3 blockade- Salivary, sweat, and lachrymal glands are blocked.
inhibition of sweat glands can lead to high body temp
Atropine uses
Antidote for cholinergic agonists
block respiratory tract secretion prior to surgery
Atropine adverse effects
Drymouth, blurred vision sandy eyes , tachycardia, constipation, urinary retention
effect on CNS: restlessness, confusion, hallucinations, delirium
Uses of Scopolamine
Prevention of motion sickness
Ipratropium
used in the treatment of chronic obstructive pulmonary disease and asthma
tropicamide
used as mydriatic for fundoscopy
produces mydriasis with cycloplegia
What is the contraindication of antimuscarinic agent?
If the patient has angle-closure glaucoma
if the patient has prostatic hypertrophy and is elderly
Ganglionic blocker
Remove the dominant control
may occur by prolonged depolarization or antagonism of nicotinic receptors
Uses of ganglion blocker
Hexamethonium was used for hypertension in the past
Replaced because of their adverse effects
Tubocurarine
nondepolarizing blocker
competitive agonist
use: as adjuvant drug in anesthesia during surgery to relax skeletal muscle
Succinylcholine
Depolarizing blocker- done by binding to nicotinic receptor and depolarizing the junction.
leads to flaccid paralysis
Used in rapid endotracheal intubation
botulinum toxin
injected locally into muscle for treatment of several diseases involving muscle spasm
inhibitor of acetylcholine release
