Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

SGU Pharmacology > Cholinergic Agonists > Flashcards

Cholinergic Agonists Flashcards

1
Q

List the different classes of cholinergic agonists

A

1. Direct-acting agonists: bind to and activate muscarinic or nicotinic receptors.

  • Some are selective for muscarinic or nicotinic receptors. Others have effects on both receptors.
  • Theraputically useful drugs preferntially activate muscarinic receptors.

2. Indirect-acting agonists: inhibit acetylcholinesterase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the muscarinic and nicotinic actions of acetylcholine

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Discuss the actions of acetylcholine on the cardiovascular system.

A

Direct effects of Acetylcholine include:

  • Vasodilation through NO synthesis
  • Decrease in cardiac rate (M2 effect)
  • Decrease in rate of conduction in the SA and AV nodes (M2 effect)
  • Decrease in force of contraction (M2 effect)

IV injection of small doses of acetylcholine cause a fall in blood pressure due to vasodilation (M3 effect) usually accompanied by reflex tachycardia.

IV injections of large doses of acetylcholine cause vasodilation, a fall in blood pressure (M3 effect) and bradycardia (M2 effect)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Discuss the effects of acetylcholine on various organ systems

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe the nicotinic effects of Acetylcholine

A

If muscarinic effects are blocked by a muscarinic antagonist such as atropine, large doses of acetylcholine produce nicotinic effects:

  • Increase in blood pressure and vasoconstriction
  • hese effects are due to stimulation of
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

List the classes of Direct Cholinergic Agonists

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe the main drugs, mechanism of action, uses and adverse effects of choline ester drugs.

A

The main choline ester drugs are:

  1. Acetylcholine
  2. Methacholine
  3. Carbachol
  4. Bethanechol

Choline esters are quaternary ammoniums and are poorly absorbed and distributed into the CNS. They differ in their susceptibility to hydrolysis by cholinesterase. Acetylcholine is very rapidly hydrolyzed. Methacholine, Carbachol and Bethanechol are more resistant to hydrolysis by cholinesterase.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

1. Acetylcholine

A

Has no systemic theraputic applications due to multiplicity of actions, and rapid hydrolysis by both acetylcholinesterase and plasma butyrylcholinesterase.

USES

  • Used to obtain rapid miosis after delivery of the lens in cataract surgery and other procedures where rapid miosis is required.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q
  1. Methacholine
A

A muscarinic agonist (worsens Asthma effects)

USES

  • Diagnosis of bronchial airway hyperactivity in subjects who do not have clinically apparent asthma.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q
  1. Carbachol
A

Both muscarinic and nicotinic agonist.

USES

  • Miosis during surgery
  • Reduces intraocular pressure after cataract surgery.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q
  1. Bethanchol
A

Muscarinic agonist.

USES

  • Postoperative and postpartum urinary retention.
  • Atony of the eurinary bladder.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the main drugs, mechanism of action, uses and adverse effects of natural alkaloid drugs.

A

The main natural alkaloids are:

1. Pilocarpine

2. Nicotine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q
  1. Pilocarpine
A

Partial muscarini agonist. Tertiary amine (noncharged so enters CNS freely). Stable to hydrolysis by acetylcholinesterase.

USES

  • Second line agent for open angle glaucoma
  • Management of acute angle-closure glaucoma
  • Treatment of dry mouth due to radiotherapy for cancer of head and neck
  • Treatment of dry mouth caused by Sjogren’s Syndrome

ADVERSE EFFECTS

The adverse effects mimic the effects of generalized cholinergic stimulation:

  • Sweating
  • Salivation
  • Flushing
  • Low blood pressure
  • Nausea
  • Abdominal pain
  • Diarrhea
  • Bronchospasm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q
  1. Nicotine
A

Tertiary amine. Selective agonist of the nicotinic receptor. Depending on the dose, nicotine depolarizes autonomic ganglia, resulting first in stimulation and then in paralysis.

USES

  • Smoking cessation therapy

ACTIONS

  • At low doses: ganglionic stimulation by depolarization
  • The response resembles simultaneous discharge of both parasympathetic and sympathetic nervous systems.
  • CV system: Mainly sympathomimetic effects. Increase HR and BP due to catecholamine release from nerve terminals and adrenal medulla
  • GI & Urinary tracts: Mainly parasympathomimetic effects: nausea, vomiting, diarrhea, voiding of urine.
  • Secretions: Stimulation of salivary and bronchial secretions
  • At high doses: ganglionic blockade and neuromuscular blockage.

ACUTE POISONING

  • Symptoms of acute, severe poisoning: nausea, salivation, abdominal pain, vomiting, diarrhea, cold sweat, mental confusion and weakness.
  • Blood pressure fall, the pulse is weak.
  • Death may occur from paralysis of respiratory muscles and/or central respiratory failure.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

List the classes of Indirect-Acting Cholinergic Agents (Anticholinesterases)

A

1. Edrophonium

2. Carbamates

A. Physostigmine

B. Neostigmine

C. Pyridostigmine

3. Organophosphates

A. Echothiophate

B. Parathion and Malathion

C. Sarin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the mechanism of action and organ system effects of the indirect-acting cholinergic agents

A

MOA: Cholinesterase inhibitors act by inhibiting acetylcholinesterase: they increase concentration of endogenous acetylcholine.

  • Edrophonium binds reversibly to the active site of the enzyme.
  • Carbamates form a covalent bond with the enzyme.
  • Organophosphates phosphorylate the enzyme. The covalent bond formed is extremely stable and hydrolyzes very slowly.
    • The phosphorylated enzyme may undergo a process called ageing.
    • This process strengthens the phosphorous-enzyme bond.
17
Q

Describe the organ system effects of acetylcholinesterases

A

Anticholinesterases amplify the action of endogenous acetylcholine. Therefore their effects are similar (but not always identical) to the effects of the direct-acting cholinomimetic agonists.

CNS: In low concentrations liposoluble cholinesterase inhibitors cause CNS activation. In higher concentrations they cause convulsions, which may be followed by coma and respiratory arrest.

EYE/RESPIRATORY TRACT/GI TRACT & URINARY TRACT: These systems are well innervated by the parasympathetic system. The effects of cholinesterase inhibitors are similar to the effects of the direct-acting cholinomimetics.

NMJ: Cholinesterase inhibitors increase the strength of contraction. Useful to reverse action of nondepolarizing neuromuscular blockers. Useful in Myasthenia Gravis.

18
Q

Describe the system effects of acetylcholinesterases on the Cardiovascular System

A
  • Cholinesterase inhibitors can activate both sympathetic and parasympathetic ganglia supplying the heart.
  • They can also activate acetylcholine receptors on cardiac and vascular smooth muscles that receive cholinergic innervation.
  • In the heart, parasympathetic effects predominate. Negative chronotropic, dromotropic, and ionotropic effects: cardiac output falls.
  • In the vascular smooth muscle, cholinesterase inhibitors have minimal effects because most vascular beds lack cholinergic innervation.
  • At moderate doses they cause an increase in systemic vascular resistance and blood pressure.
  • This is due to activation of sympathetic ganglia and central sympathetic centers.
  • The net CV effects of moderate doses of cholinesterase inhibitors consist of:
    • ​Modest bradycardia
    • Fall in cardiac output
    • Increased vascular resistance
    • Increase in blood pressure
  • Toxic doses of cholinesterase inhibitors cause marked bradycardia, significant derease of cardiac output and hypertension
19
Q
  1. Edrophonium
A

Quaternary ammonium. Does not enter CNS.

USES

  • Used in the diagnosis of myasthenia gravis. Edrophonium IV leads to rapid increase in muscle strength.
  • Used to reverse the neuromuscular block produced by non-depolarizing muscular blockers.
20
Q

2A Physostigmine

A

Tertiary amine. Can enter and stimulate the CNS.

USES

  • Treatment of overdoeses of anticholinergic drugs
21
Q

2B Neostigmine

A

Quaternary ammonium. Does not enter CNS.

USES

  • Postoperative urinary retention.
  • Reversal of effects of non-depolarizing neuromuscular blockers after surgery.
  • Treatment of mysathenia gravis.
22
Q

2C Pyridostigmine

A

Quaternary ammonium. Does not enter CNS.

USES

  • Treatment of Myasthenia Gravis.
23
Q

3A Echothiophate

A

USES

  • Rarely used for glaucoma.
24
Q

3B Parathion and Malathion (Insecticides)

A

USES

  • Insecticides
25
Q

3C Sarin (Nerve agents)

A

Among the most potent synthetic toxic agents known.

26
Q

Describe the AChE Inhibitors used in Alzheimer Disease

A
  • The mainstay of therapy for patients with Alzheimer disease is the use of centrally acting acetylcholinesterase inhibitors.
    • Donepezil
    • Rivastigmine
    • Galantamine
27
Q

Describe the mechanism by which Pralidoxime reactivates phosphorylated acetylcholinesterases.

A
  • If given before ageing has occured, drugs like pralidoxime split the phosphorous-enzyme bond.
  • Pralidoxime can be used as a cholinesterase regenerator for organophosphate insecticide poisoning.

SGU Pharmacology (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions