L11: Cholinergic Agonists

Question 1

what is ACh synthesized from

Answer 1

choline + Acetyl CoA

Question 2

ACh is released in response to ______ which increases the _______ influx

Answer 2

depolarization
Ca+

Question 3

the release of ACh sitmulates what receptors

Answer 3

nicotinic or muscarinic

Question 4

how is ACh inactivated?

Answer 4

• gets hydrolyzed by acetylcholinesterase (AChE)
• choline gets endocytosed into terminal

Question 5

all use of Bethanecol is considered

Answer 5

extra label

Question 6

what are the indications of Bethanecol

Answer 6

• decreases bladder contractility in dogs/cats
• potential GI indications…cecal displacement/dislocation in cows; equine gastric ulcer syndrome

Question 7

why is Bethanecol not a slay choice drug for large animals

Answer 7

REQUIRES COMPOUNDING
& fucks up GI
- cecal displacement/dislocation in cows
- equine gastric ulcer syndrome

Question 8

pharmacodynamics of Bethanecol (what systems does it affect most)

Answer 8

affects GI and urinary most strongly

Question 9

administration method of Bethanecol

Answer 9

PO in dogs
SC in large animals

Question 10

adverse effects of Bethanecol

Answer 10

overextension of therapeutic effect
particularly colic in horses

Question 11

contradictions of Bethanecol

Answer 11

• Obstruction - GI impaction, torsion, blocked urethra
• gastric ulcers (small animals)
• hyperthyroidism
• hypotension, bradycardia
• any animal with asthma b/c risk of bronchoconstriction
• epilepsy
• hypersensitivity
• recent GI surgery

Question 12

motor nerves release ACh onto ____ receptors of the skeletal muscle neuromuscular joints

Answer 12

Nm

Question 13

explain the signaling at neuromuscular junction

Answer 13

• motor neurons release ACh onto Nm receptors
• Na channels open and depolarize the end plate
• magnitude of voltage chance is proportional to the amount of ACh released
• once threshold is reached adjacent V-gated Na channels open, transmitting the AP along the muscle fiber and causing contraction
• ACh is broken down and Na+ channels reset
• if ACh is present in the neuromuscular junction for too long, receptors will depolarize

Question 14

Myasthenia like syndrome is an _____ attack against ______ receptors

Answer 14

autoimmune
Nm

Question 15

what is myasthenia like syndrome treated with

Answer 15

methimazole

Question 16

T/F: myasthenia like syndrome is congenital

Answer 16

T

Question 17

indications for Neostigmine use

Answer 17

treatment of GI or bladder atony (not moving), esp. following Sx
Reversal of neuromuscular blockade

Question 18

Neostigmine is labeled for use in what animals

Answer 18

sheep, swine, cattle, horses

Question 19

what is the extra label use of neostigmine

Answer 19

diagnosis and treatment of myasthenia like syndrome

Question 20

Neostigmine ROI

Answer 20

IV

Question 21

metabolism of Neostigmine

Answer 21

plasma cholinesterases and liver

Question 22

OD of what drug may cause a “cholinergic crisis”

Answer 22

Neostigmine

Question 23

elimination of neostigmine

Answer 23

primarily urinary, half life is ~40 seconds

Question 24

labeled use of Pyridostigmine bromide

Answer 24

cases w/ canine myasthenia like syndrome
extra label use in cats

Question 25

ROI pyridostigmine bromide

Answer 25

PO

Question 26

metabolism of pyridostigmine bromide

Answer 26

plasma cholinesterases and liver

Question 27

elimination of pyridostigmine bromide

Answer 27

primarily urinary
half life about 2 min

Question 28

adverse effects of pyridostigmine bromide

Answer 28

• intussusception
• tolerance due to downregulation of Nm receptors

Question 29

what are the cholinesterase inhibitors

Answer 29

• neostigmine
• pyridostigmine

Question 30

what drug is a direct acting cholinergic agonist

Answer 30

bethanechol