L11: Cholinergic Agonists Flashcards
what is ACh synthesized from
choline + Acetyl CoA
ACh is released in response to ______ which increases the _______ influx
depolarization
Ca+
the release of ACh sitmulates what receptors
nicotinic or muscarinic
how is ACh inactivated?
- gets hydrolyzed by acetylcholinesterase (AChE)
- choline gets endocytosed into terminal
all use of Bethanecol is considered
extra label
what are the indications of Bethanecol
- decreases bladder contractility in dogs/cats
- potential GI indications…cecal displacement/dislocation in cows; equine gastric ulcer syndrome
why is Bethanecol not a slay choice drug for large animals
REQUIRES COMPOUNDING
& fucks up GI
- cecal displacement/dislocation in cows
- equine gastric ulcer syndrome
pharmacodynamics of Bethanecol (what systems does it affect most)
affects GI and urinary most strongly
administration method of Bethanecol
PO in dogs
SC in large animals
adverse effects of Bethanecol
overextension of therapeutic effect
particularly colic in horses
contradictions of Bethanecol
- 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
motor nerves release ACh onto ____ receptors of the skeletal muscle neuromuscular joints
Nm
explain the signaling at neuromuscular junction
- 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
Myasthenia like syndrome is an _____ attack against ______ receptors
autoimmune
Nm
what is myasthenia like syndrome treated with
methimazole
T/F: myasthenia like syndrome is congenital
T
indications for Neostigmine use
treatment of GI or bladder atony (not moving), esp. following Sx
Reversal of neuromuscular blockade
Neostigmine is labeled for use in what animals
sheep, swine, cattle, horses
what is the extra label use of neostigmine
diagnosis and treatment of myasthenia like syndrome
Neostigmine ROI
IV
metabolism of Neostigmine
plasma cholinesterases and liver
OD of what drug may cause a “cholinergic crisis”
Neostigmine
elimination of neostigmine
primarily urinary, half life is ~40 seconds
labeled use of Pyridostigmine bromide
cases w/ canine myasthenia like syndrome
extra label use in cats
ROI pyridostigmine bromide
PO
metabolism of pyridostigmine bromide
plasma cholinesterases and liver
elimination of pyridostigmine bromide
primarily urinary
half life about 2 min
adverse effects of pyridostigmine bromide
- intussusception
- tolerance due to downregulation of Nm receptors
what are the cholinesterase inhibitors
- neostigmine
- pyridostigmine
what drug is a direct acting cholinergic agonist
bethanechol
