Cholinergic Agonists Flashcards
Why does Ach lacks therapeutic action?
Multiplicity of actions (leading to diffuse effects)
Rapid inactivation by the cholinesterases
What are the effects of Ach on heart rate and cardiac output?
Low heart rate
Low cardiac output
{Due to reduction in the rate of firing at the sinoatrial (SA) node}
Injection of ACh causes vasodilation and lowering of blood pressure by activating ____ receptor on the endothelium.
M3
How does NO produces vasodilation?
M3 receptor stimulated → Arginine to NO → protein kinase G in SMCs → hyperpolarization and SMCs relax (PDE inhibition)
______________, a direct-acting cholinergic agonist, is used to assist in the diagnosis of asthma due to its
bronchoconstricting properties
Methacholine
In the genitourinary tract, ACh __________ (increases/decreases) the tone of the detrusor muscle, causing urination
increases
In GI tract, it __________ (enhances/inhibits) secretions and motility
enchances
In the eye, ACh is involved in stimulation of ciliary muscle contraction for _______ (far/near) vision and in the constriction of the pupillae sphincter muscle, causing _________ (miosis/mydriasis)
near
miosis
ACh (1% solution) is instilled into the __________ (anterior/posterior) chamber of the eye to produce miosis during ophthalmic surgery
anterior
_____________ lacks nicotinic actions (due to addition of the methyl group), but does have strong muscarinic activity
Bethanechol
__________ has about a 1-hour duration of action
bethanechol
bethanechol is used to _________ (stimulate/inhibit) the atonic bladder
stimulate
____________ is used for postpartum or
postoperative, nonobstructive urinary retention
bethanechol
Adverse effects of cholinergic agonists?
Nausea Diarrhea Bronchospasm Urinary urgency Miosis
Carbachol’s intraocular use provides miosis for eye surgery and _________ (increase/decrease) intraocular pressure in the treatment of glaucoma
decrease
Which one is more potent?
Carbachol OR Pilocarpine
carbachol
___________ can penetrate into CNS (carbachol/bethanechol/pilocarpine)
pilocarpine
The drug of choice for EMERGENCY lowering of intraocular pressure of both open-angle and angle-closure glaucoma is _____________ (pilocarpine/carbachol)
pilocarpine
How does pilocarpine lowers IOP?
Pilocarpine is extremely effective in opening the trabecular meshwork around the Schlemm canal, causing an immediate drop in intraocular pressure because of the increased drainage of
aqueous humor.
Onset of action and duration of action for pilocarpine
Onset = few minutes Duration = 4 to 8 hours
What r agents other than pilocarpine that can be used to treat glaucoma?
Dorzolamide and Timolol, are effective in treating glaucoma but are not used for emergency lowering of intraocular pressure
Carbachol
__________ is beneficial in promoting salivation in patients with xerostomia resulting from irradiation of the head and neck
pilocarpine
___________, which is characterized by dry mouth and lack of tears, is treated with oral pilocarpine tablets and cevimeline
Sjögren syndrome
___________ can cause blurred vision, night blindness, and brow ache
pilocarpine
Poisoning with __________ is characterized by
exaggeration of various parasympathetic effects which can be counteracted by parenteral atropine
pilocarpine
The effects of pilocarpine are similar to those produced by consumption of mushrooms of the genus ________
Inocybe
Summarise the cholinergic agonists
- Ach
- Bethanechol
- Carbachol
- Pilocarpine
- Ach for miosis in ophthalamic surgery
- Bethanechol for tx of urinary retention
- Carbachol for miosis and lowering IOP for glaucoma
- Pilocarpine for emergency tx of glaucoma
Excess of edrophonium can cause ___________
cholinergic crisis
What is edrophonium
Reversible cholinesterase inhibitor
Edrophonium is used for the diagnosis of ________________
myasthenia gravis
IV injection of edrophonium rapidly ___________ (increases/decreases) the strength of the muscle which confirms the dx of myasthenia gravis
increases
Edrophonium also ___________ (reverse/enhance) neuromuscular blocking effects of drugs
reverse
Edrophonium is a ________ (short/intermediate) acting drug
short (10-20min)
Physostigmine and neostigmine are __________ (short/intermediate) acting drugs
intermediate
_____________ is contraindicated in intestinal and urinary nonobstructive retention
neostigmine
WHich one of the following enters CNS?
Physostigmine or neostigmine
physostigmine (so it produces paralysis of skeletal muscles if given in high doses)
Adverse effects of physostigmine
Convulsions and skeletal muscle paralysis
___________ is used for the chronic management of myasthenia gravis
pyridostigmine
duration of action of pyridostigmine is _________
3-6 hrs
tacrine is not used for tx of AD bcz of ____________
hepatotoxicity
Donepezil, rivastigmine, and galantamine all are used to delay progression only but can’t stop ___________________
Alzheimers disease
_________ is used for postoperative abdominal distention and for gastric atony following bilateral vagotomy
Bethanechol
parenteral (IV or IM) administration of ___________ (carbachol/bethanechol) may cause cardiac arrest
bethanechol
Patients with no clinically apparent asthma are ______ (more/less) sensitive to methacholine-induced bronchoconstriction than normal patients
more
When used before surgery to treat acute narrow-angle glaucoma, pilocarpine is often given in combination with an indirectly acting muscarinic agonist such as ______________
physostigmine
What r the contraindications of direct acting cholinergic agonists?
Peptic ulcer Asthma Cardiac disease Parkinson disease Hyperthyroidism Mechanical obstruction of the GI or urinary tract
Nicotine-based products and varenicline (Chantix), direct-acting nicotinic receptor agonists, are approved for use in _________ cessation
smoking cessation
_________ acts as an antidote for organophosphorus insecticide and nerve gas poisoning
Pralidoxime
Postoperative ileus and congenital megacolon, and urinary tract retention can be treated with direct or indirectly acting cholinomimetic drugs such as ___________ and _____________
bethanechol
neostigmine
____________ are also used to increase the tone of the lower esophageal sphincter
Bethanechol and neostigmine
Myasthenia gravis is an autoimmune disease in which antibodies complex with ____________ receptors at the neuromuscular junction to cause skeletal muscle
weakness and fatigue
nicotinic
Adverse effects of cholinergic agonists
Mnemonic - DUMBBELS
Diarrhea Urination Miosis Bradycardia Bronchorrhea Emesis Lacrimation Salivation
Myasthenia gravis can be diagnosed using the __________ test, which can also assess the adequacy of treatment with AChE inhibitors
Tensilon
In tensilon test, if there is no effect, or
if muscle weakness increases, the dose of the AChE inhibitor is too ________ (high/low)
high
____________ can be used following surgery to reverse neuromuscular blockade and paralysis resulting from adjunct use of nondepolarizing agents
Neostigmine or edrophonium
Atropine and scopolamine poisoning that results in severe body temperature elevation or tachycardia can be treated with ____________(physostigmine/neostigmine), which reverses the central and the peripheral effects of competitive muscarinic antagonists
physostigmine
Many lipid-soluble ____________ are used as insecticides or nerve gases and may be absorbed in sufficient quantities from the skin or lungs to cause cholinergic intoxication
organophosphates
Examples of agents that cause cholinergic intoxication
- insecticides
- nerve gas
insecticide = malathion
nerve gas = sarin gas
What is the treatment of cholinergic intoxication?
(1) Maintain respiration and decontaminate to prevent further absorption.
(2) Administer atropine parenterally to inhibit muscarinic effects.
(3) Administer pralidoxime within minutes of exposure.
Choline uptake is inhibited by _____________
hemicholinium
____________ interacts with synaptobrevin and other proteins to prevent ACh release
Botulinum toxin
__________ is used for tx of blepharospasm, strabismus/hyperhidrosis, dystonia, and cosmetics
Botulinum
What are the uses of edrophonium?
Dx of MG
Antidote for competetive NM blockers
What r the uses of neostigmine?
tx of MG
tx of postoperative abd distention and urinary retention
antidote for competetive NM blockers
What are the uses of physostigmine?
Reverses CNS effects of atropine
Reverses CNS and CVS effects of TCA
Increases bladder and intestinal motility
Echothiophate is used in the tx of ___________ glaucoma
open angle
