Cholinergic Drugs and Neuromuscular Blockers

Question 1

What do cholinergic drugs act on?

Answer 1

Acetylcholine (ACh) receptors

Question 2

Which nervous systems have acetylcholine receptors?

Answer 2

Parasympathetic, Sympathetic, and Somatic Nervous Systems

Question 3

Where does ACh synthesis occur?

Answer 3

In the presynaptic cell

Question 4

Which enzyme synthesizes ACh?

Answer 4

Choline acetyltransferase

Question 5

What are the precursors for ACh synthesis?

Answer 5

Acetyl coenzyme A and choline

Question 6

Where is ACh stored before release?

Answer 6

In synaptic vesicles in the presynaptic cell

Question 7

Why is ACh stored in synaptic vesicles?

Answer 7

To protect it from degradation and keep it ready for release

Question 8

What triggers ACh release?

Answer 8

An action potential when the snyaptic vesicle fuses to the snyaptic memrbane

Question 9

How many vesicles fuse to release ACh in one signaling event?

Answer 9

100 or more

Question 10

Where does ACh bind after being released?

Answer 10

To receptors on the postsynaptic cell

Question 11

What are the two types of acetylcholine receptors?

Answer 11

Nicotinic ACh receptors (nAChR) and muscarinic ACh receptors (mAChR)

Question 12

How is ACh degraded?

Answer 12

By the enzyme acetylcholinesterase (ACE)

Question 13

What happens to ACh after its metabolized?

Answer 13

It is broken down into choline and acetate

Question 14

How fast does acetylcholinesterase break down ACh?

Answer 14

Within 150 microseconds of release

Question 15

What happens to choline after ACh is broken down?

Answer 15

It is scavenged by transporters on the presynaptic cell and recycled for ACh synthesis

Question 16

How is bethanechol administered?

Answer 16

Orally, intramuscularly (i.m.), or intravenously (i.v.)

Question 17

What is the effect of a muscarinic ACh receptor (mAChR) agonist?

Answer 17

Activates the receptor, mimicking parasympathetic nervous system activation (parasympathomimetic)

Question 18

Why do some muscarinic agonists have prolonged effects?

Answer 18

They are completely resistant to acetylcholinesterase (ACE), preventing breakdown

Question 19

What is the main therapeutic use of bethanechol?

Answer 19

Treats loss of bladder smooth muscle tone (e.g., post-surgery or post-labor)

Question 20

How does bethanechol help with xerostomia?

Answer 20

Stimulates salivation from parotid, submandibular, and sublingual glands

Question 21

How does bethanechol restore bladder function and what dose it activate?

Answer 21

Activates muscarinic receptors in the bladder, causing smooth muscle contraction and urination

Question 22

What is an off-label use of bethanechol?

Answer 22

Treatment of xerostomia (dry mouth)

Question 23

How is carbachol administered?

Answer 23

As eye drops

Question 24

What receptors does carbachol activate?

Answer 24

Primarily muscarinic ACh receptors, but also nicotinic ACh receptors

Question 25

What is carbachol used to treat?

Answer 25

Wide-angle glaucoma

Question 26

How does carbachol reduce intraocular pressure?

Answer 26

Causes contraction of smooth muscle around canals of Schlemm, opening them to drain excess aqueous humor

Question 27

How is pilocarpine administered?

Answer 27

As eye drops (topically) or orally

Question 28

What happens if intraocular pressure is too high?

Answer 28

It compresses retinal arteries, leading to retinal death

Question 29

What is pilocarpine used for?

Answer 29

Reduces intraocular pressure in wide-angle glaucoma

Question 30

What is an additional use of pilocarpine?

Answer 30

Treatment of xerostomia (oral form, Salagen)

Question 31

What does a muscarinic ACh receptor (mAChR) antagonist do?

Answer 31

Competes with ACh for receptor binding, preventing activation

Question 32

What are the effects of muscarinic ACh receptor antagonists?

Answer 32

Opposite of parasympathetic activation (antimuscarinic effects)

Question 33

What are common antimuscarinic side effects?

Answer 33

Drowsiness, dry mouth, urinary retention

Question 34

Which drug classes can block mAChRs?

Answer 34

Antihistamines, antipsychotics, antidepressants

Question 35

What common medications contain antihistamines?

Answer 35

Many cold medications and over-the-counter sleep aids

Question 36

Why is it illegal to drive after taking antihistamines in Virginia (VA)?

Answer 36

They cause drowsiness, impairing driving ability

Question 37

How do antihistamines interact with alcohol?

Answer 37

They enhance CNS depression caused by alcohol

Question 38

How is atropine administered?

Answer 38

Intravenously (i.v.) or orally

Question 39

How does atropine work?

Answer 39

Competes with ACh for receptor binding, preventing signaling

Question 40

What are the therapeutic uses of atropine?

Answer 40

Preanesthetic: decreases respiratory secretions (antisialogogue) Dilates bronchial passages Reverses life-threatening bradycardia (slow heart rate)

Question 41

Does atropine affect the CNS at clinical doses?

Answer 41

No

Question 42

How is scopolamine administered?

Answer 42

Subcutaneously (s.c.), intravenously (i.v.), or transdermally

Question 43

How does scopolamine work?

Answer 43

Competes with ACh for receptor binding, relaxing smooth muscle

Question 44

How does scopolamine differ from atropine?

Answer 44

It also has CNS effects in addition to atropine’s effects

Question 45

What are the therapeutic uses of scopolamine?

Answer 45

Preanesthetic: decreases the amount of anesthesia needed Motion sickness treatment (Transderm-Scop patch behind the ear)

Question 46

How does scopolamine prevent motion sickness?

Answer 46

Blocks vestibular input (inner ear to brain) Inhibits brainstem chemoreceptor trigger zone Prevents the vomit reflex

Question 47

What precautions should be taken with scopolamine?

Answer 47

Wash hands after applying Leave patch on for 4 hours after event Strongly enhances depressant effects of alcohol

Question 48

How do Acetylcholinesterase (ACE) inhibitors work?

Answer 48

Prevent ACh degradation, causing ACh accumulation in the synapse

Question 49

What is the effect of ACE inhibitors on ACh receptors?

Answer 49

Tonic activation of ACh receptors

Question 50

How is neostigmine administered?

Answer 50

Orally, subcutaneously (s.c.), intramuscularly (i.m.), or as eye drops

Question 51

How does neostigmine enhance ACh signaling?

Answer 51

Prevents ACh breakdown, amplifying the signal

Question 52

What conditions is neostigmine used to treat?

Answer 52

Postoperative urinary retention Wide-angle glaucoma

Question 53

What is Myasthenia Gravis?

Answer 53

An autoimmune neuromuscular disease where the body makes antibodies against nicotinic ACh receptors at the neuromuscular junction

Question 54

How does neostigmine help Myasthenia Gravis patients?

Answer 54

Increases ACh levels in the synapse, compensating for fewer ACh receptors and enhancing muscle stimulation

Question 55

What are the reversible and irreversible anticholinesterase drugs?

Answer 55

Reversible: - neostigmine Irreversible: - organophosphates

Question 56

What is the main danger of irreversible ACE inhibitors?

Answer 56

Causes paralysis, including diaphragm paralysis, leading to respiratory failure

Question 57

What are organophosphates primarily used for?

Answer 57

Pesticides (e.g., Acephate, Chlorpyrifos, Malathion, Trichlorfon)

Question 58

How are organophosphates used in warfare?

Answer 58

As nerve agents (e.g., Sarin, Tabun, Soman, VX)

Question 59

Which nervous systems do neuromuscular blockers affect?

Answer 59

Parasympathetic, sympathetic, and central nervous systems

Question 60

How much nerve agent is lethal?

Answer 60

As little as 200 μg

Question 61

Which drug is used as an antidote for organophosphate poisoning?

Answer 61

Atropine

Question 62

How does atropine counteract organophosphate poisoning?

Answer 62

Blocks muscarinic receptor effects, reducing toxic overstimulation

Question 63

How do nicotinic receptor antagonists work?

Answer 63

Block ACh binding at nicotinic receptors, preventing muscle contraction

Question 64

How does d-tubocurarine work?

Answer 64

Competitively binds to ACh sites but does not cause depolarization

Question 65

Does d-tubocurarine affect consciousness?

Answer 65

No, it does not cross the blood-brain barrier (BBB)

Question 66

What effect does d-tubocurarine have on muscles?

Answer 66

Causes complete skeletal paralysis

Question 67

What is d-tubocurarine used for?

Answer 67

Adjunct to anesthesia to reduce anesthetic requirements Decreases respiratory and cardiac depressive side effects of anesthesia

Question 68

How does succinylcholine work?

Answer 68

Mimics ACh, causing initial depolarization followed by receptor desensitization

Question 69

What effect does succinylcholine have on muscles?

Answer 69

Complete skeletal paralysis

Question 70

How is succinylcholine metabolized?

Answer 70

By acetylcholinesterase (ACE), leading to a brief duration of action, which is fast

Question 71

What is succinylcholine used for?

Answer 71

Intubation Electroshock therapy

Question 72

What is the phase I of succinylcholine’s effect?

Answer 72

Prolonged ACh receptor stimulation → disorganized contractions (fasciculations)

Question 73

What is the phase II of succinylcholine’s effect?

Answer 73

ACh receptor desensitization, preventing new action potentials (main anesthetic effect)