Cholinergic Drugs

Question 0

Cholinergic Agonists: What happens when the nicotinic receptors are activated?

Answer 0

Muscle contraction

Question 1

Cholinergic Agonist: What are responses when muscarinic receptors are activated?

Answer 1

Eye: Miosis (constriction of pupil)
Cardiovascular: Decrease in the heart rate
Respiratory: Bronchial Constriction and increased secretion
Gastrointestestinal: Increased motility; relaxation of sphincter
Genitourinary: Relaxation of sphincter and bladder wall contraction
Glands: Increased secretion

Question 2

What is MOA?

Answer 2

Mechanism of Action

Question 3

What is the MOA of Direct Acting Cholinergic Agonist?

Answer 3

They act by binding directly to cholinergic receptors

Example: Pilocarpine - Pilocar –> used to treat glaucoma

Question 4

What is MOA of Indirect-Acting Cholinergic Agonists (Anticholinesterases)?

Answer 4

They inhibit the enzyme, acetylcholinesterase (AChE) whic terminates the action of acetylcholine. Thus they prolong the lifetime of acetylcholine… ***Enzyme may be inhibited either reversibly or irreversibly.

Question 5

What are Reversible Inhibitors of acetylcholinesterase enzyme used for and how/why?

Answer 5

Used with Myasthenia Gravis (MG) in which there is an autoimmune destruction of acetylcholine receptors in the neuromuscular junction - **Edrophonium - Tensilon –> used in diagnosis of MG
— or —
Used in Alzheimer’s Disease in which there is a deficiency of cholinergic neurons. These drugs prolong the action of acetylcholine thereby reduce the loss of cognitive functioning in Alzheimer’s Disease - **Donezepil - Aricept

Question 6

With Reversible Inhibitors of acetylcholinesterase enzyme, what drug is used for Myasthenia Gravis?

Answer 6

***Edrophonium (Tensilon)

Used when there is autoimmune destruction of acetylcholine receptors in neuromuscular junction

Question 7

With Reversible Inhibitors of acetylcholinesterase enzyme, which drug treats Alzheimer’s?

Answer 7

***Donezepil (Aricept)
Used when there is a deficiency of cholinergic neurons. These drugs prolong the action of acetylcholine thereby reduce the rate of loss of cognitive functioning in Alzheimer’s disease…

Question 8

What are Irreversible Inhibitors of acetylcholinesterase enzyme and what do they do?

Answer 8

They phosphorylate the enzyme cholinesterase and inactivate it permanently. Many are extremely toxic. Widely used as insecticides and commonly referred to as nerve gas.
The organophosphates are lipid soluble, they rapidly cross all membranes, including skin and blood-brain barrier. No therapeutic uses…

Question 9

What are toxic symptoms of organophosphate poisoning?

Answer 9

SLUDGE

Salivation, Lacrimation, Urination, Diarrhea, GI Upset, Emesis (vomiting)

Question 10

What two drugs are used to treat organophosphate poisoning? What is there MOA?

Answer 10

***Pralidoxime - hydrolyzes the phosphate bond and reactivates the enzyme.

***Atropine - blocks the effects of acetylcholine

Question 11

What do Cholinergic Antagonists do?

Answer 11

These drugs antagonize (inhibit or block) the effects of acetylcholine.

1. The most useful group selectively block muscarinic receptors of the parasympathetic nerves.
2. Ganglionic blockers show a preference for the nicotinic receptors of the sympathetic and parasympathetic ganglia.
3. Neuro-muscular blocking agents interfere with the transmission of efferent impulses to skeletal muscles. Used as skeletal muscle relaxant during anesthesia during surgery, intubation, and various orthopedic procedures.

Question 12

What happens when you block the muscarinic receptors?

Answer 12

Eye - mydriasis (dilation of pupil), cycloplegia (results in blurred vision)
Skin - reduced sweating, flushing
GI - reduced motility and secretions
Cardiovascular - increased heart rate (high doses)
Respiratory - bronchial dilation and decreased secretion
GU- urinary retention

Question 13

What are the side effects of cholinergic antagonists?

Answer 13

dry mouth, dry eyes, blurred vision, constipation, and urinary retention

Question 14

What are common muscarinic antagonists?

Answer 14

• **Atropine - pre-anesthetic to prevent respiratory secretions, treatment of Parkinsonism, severe bradycardia
• **Scopolamine (Scopolamine) - used to prevent motion sickness (transdermal patch)
• **Ipratropium (Atrovent) - used to treat obstructive pulmonary disease (COPD) to produce bronchodilation
• **Trihexyphenidyl (Artane) - Parkinsonism

Question 15

Drug classification and uses: Atropine

Answer 15

muscarinic antagonist

uses: pre-anesthetic to prevent respiratory secretions, treatment of Parkinsonism, severe bradycardia, enuresis

Question 16

Drug classification and uses: Scopolamine (Scopace)

Answer 16

muscarinic antagonist

uses: to prevent motion sickness (transdermal patch)

Question 17

Drug classification and uses: Ipratropium (Atrovent)

Answer 17

muscarinic antagonist

uses: chronic obstructive pulmonary disease (COPD) to produce bronchodilation

Question 18

Drug classification and uses: Triheyphenidyl (Artane)

Answer 18

muscarinic antagonist

uses: Parkinsonism

Question 19

Cholinergic Antagonist: What is the MOA of Neuromuscular Blockers?

Answer 19

These drugs block the effect of acetylcholine by interacting with the nicotinic receptors at the neuromuscular junction. They produce skeletal muscle relaxation. Clinically used during surgery for producing complete muscle relaxation.

Question 20

Drug classification and uses: Succinylcholine (Anectine)

Answer 20

cholinergic antagonist; neuromuscular blocker
use: ideal for intubation because of rapid onset and short duration. Adjunct to anesthesia… Only depolarizing factors

Question 21

Cholinergic Antagonists: Ganglion Blockers MOA

Answer 21

These drugs block the action of acetylcholine at the nicotinic receptors of all autonomic ganglia of both sympathetic and parasympathetic systems thereby blocking the entire output of the ANS - Rarely used clinicially