Parasympathetic System - Direct acting Flashcards
Parasympathomimetics
Drugs that stimulate parasympathetic nervous system through modulation of cholinergic receptors or ACh.
what are the 3 muscarinic parasympathomimetics?
Acetylcholine
Muscarine
Policarpine
You would like to perform ocular surgery on a patient? Which drug would you use and why?
Acetylcholine to obtain miosis. It does however have bradycardia and hypotension as side effects.
A patient gets mushroom poisoning from muscarine ingestion. Which side effects would he present with?
SLUDGE BBB/ DUMBELLS
What is policarpine’s clinical indication?
It can be used to treat glaucoma and ocular hypertension by allowing excess fluid to drain from the eye. As a side effect it causes eye spasms.
What is the action of direct nicotinic drugs on recepetors?
Direct interaction with cholinergic receptors to promote parasympathetic activity
In the case of cessation of smoking would you use Nicotine or Varenicline drugs?
Nicotine because it’s side effects include allergic reactions, coughing and increased salivation whereas Varenicline induces vomiting, causes nausea and there is increased risk of suicidal ideation.
A patient is about to undergo surgery. Which drug would you administer and why?
syn. succinylcholine because it is a depolarizing neuromuscular blockade. Depolarizing neuromuscular blockers are drugs used to induce anesthesia and relax skeletal muscles (paralysis) during intubation, mechanical ventilation, and surgical procedures
How do indirect cholinesterases work?
Drugs that decrease the ACh metabolism
They blocks AChE-mediated metabolism
of ACh resulting in increased synaptic ACh, boosting cholinergic function.
To reverse the actions of a depolarizing neuromuscular blockade that can cross through the blood brain barrier, which drug would you use?
Donepezil
Which other clinical implication does Donepezil have?
It is used to treat Alzheimers disease as it’s a drug that targets the Central Nervous System.
What are the PERIPHERAL side effects of using neostigmine and pyridostigmine?
SLUDGE BBB/ DUMBELLS
For a longer reversal of depolarizing neuromuscular blockades, would you use neostigmine or pyridostigmine?
Pyridostigmine.
Does preventing neuromuscular junction transmission prevent pain?
No
To aid with pain prevention, add anesthetics and analgesics to help prevent anaesthesia awareness as well.
What is the difference between depolarized and non-depolarized neuromuscular blockades?
Non- depolarizing:
Paralyses muscles but does NOT depolarize motor endplate.
Depolarizing
Paralyses muscles by depolarising motor endplate
Describe the mechanism of action of depolarizing neuromuscular blockades.
nAChR agonist
▪ Two ACh molecules bound by acetyl groups
▪ Allows for slower removal
▪ Binds to and activates nAChR, which depolarises
muscle cells, causing muscle fasciculations
▪ Muscle cells lose excitability because repolarisation
does not occur
▪ Further ACh binding does not cause
depolarisation
▪ Muscle paralysis follows fasciculations
Describe the mechanism of action of non-depolarizing neuromuscular blockades.
Competitive cholinergic antagonist
▪ Blocks nAChR at the motor endplate
▪ ACh cannot bind and activate nAChR
▪ Paralysis of muscle in characteristic order
▪ Extrinsic eye muscle
▪ Small muscle of face, limbs and pharynx
▪ Respiratory muscles
▪ Some may also reduce ACh release
Organize the following non-depolarizing neuromuscular blockades by length of activity. From short to intermediate.
Cisatracurium, Mivacurium ,Rocuronium ,Atracurium.
Mivacurium - S
Atracurium - IM
Rocuronium -IM
Cisatracurium - IM
What is the common side effect of all non-depolarizing neuromuscular blockades?
post-paralysis muscle weakness and hypotension & flushing( M&A)
What causes hypotension and flushing with the use of Mivacurium and Atracurium?
The release of histamines.
What is the name of the ONE depolarizing neuromuscular blockade? What is its mechanism of action?
Syn. succinylcholine
Onset: ~30
seconds
Duration: ~10
minute
Scoline apnoea refers to:
Scoline apnoea
Rare extended paralysis with suxamethonium chloride
A patient presents with difficulty breathing and maintained paralysis after a surgery. What are they suffering from and how can it be treated?
Scoline apnoea
Maintain artificial ventilation until metabolised
Which enzyme is responsible for the metabolism of syn. succinylcholine? Explain the mechanism that leads to Scoline apnoea.
butyrylcholinesterase
Butyrylcholinesterase activity is poor due to genetic
abnormality
▪ Poor metabolism of butyrylcholinesterase-associated
drugs (e.g. muscle relaxant suxamethonium chloride)
▪ Prolonged paralysis due to slow metabolism
▪ Breathing complications due to respiratory muscles
