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Cholinergics
whole lecture
23
Medical
Graduate
08/28/2013

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Term
M1 receptor
Definition

mech: inc IP3+DAG and [Ca++]

 

action: activates/stims myenteric plexus

Term
M2 receptor
Definition

mech: opens K+ channels / dec cAMP, dec Ca++ 

 

action: dec HR and contraction / inhibit NE release from symp nerve terminals

Term
M3 receptor
Definition

mech: inc IP3+DAG and [Ca++]

 

action: 

 - contracts circular muscle (pupil constric)

 - contracts ciliary muscle (near focus)

 - contracts brochiolar muscle, GI SM, uterine muscle, blatter detrusor 

 - relaxes vasc muslce (via NO from endo)

 - stims secretions of GI tract, eccrine sweat glands, tear glands, salivary glands, pancreatic fluids, liver bile

Term
Nicotinic Receptors
Definition

Nn: neuronal, located in symp and para postganglionic cells as well as in cortical and subcortical nuclei in the brain

 

Nm: membranes of skeletal muscles

Term
Nicotine
Definition
  • trade: 
  • half-life:
  • MoA: stims Nn receptors
  • Elim:
  • Rx: withdrawal symtpoms of smoking cessation
  • tox: 
  • notes: bc nic recs on post-gang cells of both SNS and PNS, can activate both systems simultaneously
Term
Succinylcholine
Definition
  • trade: 
  • half-life: 
  • MoA: Nm blocker. depolarization block
  • Elim: butyrl cholinesterase
  • Rx: muslce relaxant during intubation or electroconvulsive shock therapy 
  • tox: 
  • contras: fam history of familial hyperthermia, skeletal muscle myopathies
Term
Acetylcholine
Definition
  • trade: 
  • half-life: 150sec (RAPID!)
  • MoA: binds M and N receptors
  • Elim: AchE
  • Rx: none--not used clinically.
  • tox: 
  • note: quaternary nitrogen analog
Term
methacholine
Definition
  • half-life: short, but longer than Ach
  • MoA: Musc agonist
  • Elim: AchE
  • Rx: to Dx bronchial hyperactivity in pts suspected of having asthma
  • tox: bronchiolar constriction
  • contras: pts given B-blockers
  • note: quaternary nitrogen analog (no xBBB)
Term
Carbachol
Definition
  • half-life: long
  • MoA: nic and musc agonist
  • Elim: AchE (but resistant)
  • Rx: miotic agent in ocular surgery, to reduce pressure following ocular surgery
  • tox: xs nic and musc activation
  • notes: quaternary nitrogen analog
Term
Bethanechol
Definition
  • trade
  • half-life
  • MoA: musc agonist (esp GI and urinary bladder)--very little M2 activity. LACK of nic activity*
  • Elim
  • Rx: treat post-op or post-partum urinary retention, treat bladder atony
  • tox: bradycardia
  • contra: peptic ulcer, asthma, bradycardia
  • notes: quaternary nitrogen analog
Term
pilocarpine
Definition
  • half-life: ~1hr
  • MoA: pure musc agonist
  • Elim
  • Rx: narrow angle glaucoma, dry mouth (due to head and neck radiotherapy or Sjogren's syndrome)
  • tox
  • notes: "pile guacemole (glaucoma) in his dry mouth"
    • also, crosses BBB
    • NATURALLY OCCURING TERTIARRY AMINE
Term
neostigmine
Definition
  • half-life:
  • MoA: reversible cholinesterase (AchE) inhibitor!
  • Elim:
  • Rx: mysasthenia gravis, reverse neuromuscular blockade
  • tox: xs Ach action at musc and nic sites
  • contras: intestinal obstruction
  • notes: poorly xBBB
Term
edrophonium
Definition
  • half-life: ~10min (rapid onset, short duration of action...good for diag)
  • MoA: reversible AchE inhibitor
  • Elim
  • Rxdiag of myasthenia gravis vs cholinergic crisis, reversal of neuromusc block
  • tox: bradycardia
  • contras: mechanical block of intestine and urinary tract
Term
physostigmine
Definition
  • half-life: up to 2hrs
  • MoA: reverisble AchE inhibitor
  • Elim: 
  • Rx: counteract delirium associated w xs Ach activation--antidote for Musc antagonist poisoning
  • tox: xs Ach at musc and nic sites
  • contras: asthma, cardiac insufficiency, gut obstruction
  • notes: readily xBBB
Term
donepezil
Definition
  • half-life: 70hrs (long!)
  • MoA: reversible AchE inhibitor
  • Elim: 
  • Rx: Alzheimer's Dx
  • tox: 
  • contras: 
Term
organophosphate (cholinesterase inhibitor) poisoning--symptoms
Definition

Diarrhea

Urinary frequency and incontinence

Miosis

Bradycardia

Bronchorrea/Bronchoconstriction

Emesis

Lacrimation

Laxation

Salivation

Term
pralidozimine (2-PAM)
Definition
  • half-life: 75min
  • MoA: peripheral AchE reactivator
  • Elim: 
  • Rx: respiratory muscle weakness in organophosphate poisoning
  • tox: 
  • contras: 
Term
treatment of organophosphate poisoning
Definition

1. mechanical VENTILATION to counter effects on neurmusc junction

2. SUCTION of oral secretions

3. ATROPINE to protect from systemic muscarinic effects

4. pralidoximine chloride (2-PAM)

Term
echothiophate
Definition
  • half-life: very long
  • MoA: irreversible AchE inhibitor
  • Elim: 
  • Rx: produce long-term miosis in treatment of open angle glaucoma
  • tox: 
  • contras: 
Term
atropine
Definition
  • half-life: 
  • MoA: muscarinic antagonist
  • Elim: 
  • Rx: 
    • 1. to allay urg and freq of micturition
    • 2. relieve hypermotility of colon and hypertonicity of SI
    • 3. treatment of AchE inhibitor induced poisoning
    • 4. induce mydriasis and cycloplegia (paralysis of ciliary muscle)
    • 5. reverse bradycardia of vagal origin
  • tox: 
  • contras: 
Term
atropine poisoning
Definition
"blind as a bat, mad as a batter, red as a beet, hot as a hare, dry as a bone, the bowel and the pladder lose their tone, and the heart runs alone."
Term
scopolamine
Definition
  • half-life: 
  • MoA: muscarinic antagonist
  • Elim: 
  • Rx: motion sickness, anti-salilgogue (to minimize secretions) in surgery
  • tox: 
  • contras: narrow angle glaucoma
Term
glycopyrrolate
Definition
  • half-life
  • MoAmuscarinic antagonist
  • Elim
  • Rxto prevent overstim of gut during reversal of neuromusclular blockade
  • tox
  • contras
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