Cholinergics Flashcards
Direct muscarinic agonist + clinical use
Pilocarpine: glaucoma and dry mouth
Bethanechol: gastric atony
What drug is pilocarpine and how does it work?
Direct muscarinic agonist: contraction of sphincter muscles, contract ciliary muscles and promotes salivation
What drug is bethanechol and how does it work?
Promotes GI motility and secretion
Direct nicotinic agonist + clinical use + mechanism
Low dose nicotine: Skeletal muscle contractions, increases HR and GI motility
Aid to smoking cessation
What is organophosphate poisoning
Caused by organophosphates commonly found in nerve gases and certain insecticides.
The phosphate group interferes with the function of cholinesterase (breaks down Ach) by binding to it. Excessive acetylcholine in the synapse causes continuous stimulation of the target cells.
Clinical manifestations:
S: salivation
L: lacrimation (tearing)
U: urination
D: defecation
What is the treatment for organophosphate poisoning?
- Pralidoxime before ‘ageing’ process
- Atropine + Physostigmine (treat acute atropine poisoning) to reverse muscarinic effects since atropine is direct anti-muscarinic
Direct anticholinergic drugs + Clinical use
A: Atropine - bradycardia
B: Benztropine - Parkinson’s
S: Scopolamine - motion sickness
I: Ipratropium - FIRST LINE FOR COPD
O: Oxybutynin - urinary incontinence
Mnemonic:
i see ABS I O
Describe atropine
Non selective muscarinic acetylcholine receptor antagonist
M1: reduce acid secretion and CNS confusion
M2: increase HR (hence used to treat bradycardia)
M3: reduce gland secretion and GI motility
Uses: bradycardia, organophosphate poisoning and opthalmic examinations
What is the adverse effect of atropine (HINT ITS A POEM)
Red as a beet, blind as a bat, dry as a bone, hot as a hare and mad as a hatter
Describe ipratropium
Inhaled anticholinergic agent.
M3: decrease bronchoconstriction (used to treat COPD)
Minimal adverse effects
Name the indirect anticholinergic drugs
Depolarising blockade:
High dose nicotine
Non-depolarising NMBA:
Pancuronium
Depolarising NMBA:
Succinylcholine
Pre-synaptic toxin (decrease Ach):
Botulinum Toxin
Describe the depolarising blockade of nicotine
Membrane depolarizes to open the channel, exciting the muscles continously. This results in fasciculations and muscle spasms.
This desensitises the receptor so when it repolarizes, there is a sustained muscle relaxation = flaccid paralysis
What is pancuronium?
Competitive antagonist of Nm nicotine acetylcholine receptors.
Used for surgical paralysis
What is succinylcholine + what is its biggest risk
Depolarising blockade: same as high dose nicotine.
Risk of sleep apnea
Used for surgical paralysis
List 3 non-comestic uses of botulinum toxin
Cervical dystonia
Blepharospasm
Spasticity
