Skeletal muscle relaxants acting on the NMJ Flashcards
Name the non-depolarising skeletal muscle relaxants?
Competitive antagonists of Nm
- Isoquinolines
D-tubocurarine Mivacurium Cistracurium Atracurium Doxacurium
Which non-depolarising SM relaxant is metabolised by Pseudocholinesterase?
Mivacurium
How are Cistracurium and Atracurium metabolised?
Spontaneous (Hoffmann-elimination)
Which non-depolarising skeletal muscle relaxants are metabolised spontaneously?
Cistracurium and atracurium
What is the duration of action of Mivacurium?
Short acting (10-15 mins)
What is the duration of action of Cistracurium?
Intermediate acting (20-30 mins)
What is the duration of action of Atracurium?
Intermediate acting (15-35 mins)
What is the duration of action of Doxacurium?
Long acting
What is the duration of action of D-tubocurarine?
> 35 mins
Which drug is safe in renal and hepatic impairment?
Why?
Atracurium
Because it is spontaneously inactivated to Laudonosine (therefore does not use the liver or kidneys in its metabolism)
What is the break down product of Atracurium?
Laudonosine
In which patients do we not use Mivacurium?
In those who are quick metabolisers (pseudocholinesterase). It already has a short duration of action.
How do you reverse the block induced by non-depolarising SM relaxants?
Competitive non depolarising SM relaxants are competitive so you over come the effects by increasing the concentration of the ligand of the receptor; in this case, Ach - so you use an AchE inhibitor.
You use Neostigmine (quartenary AchE inhibitor) - cannot enter the CNS.
Not physostigmine as it is a tertiary amine and can enter the CNS
Not Edrophonium as it has a short half life.
Name the non-depolarising SM relaxants?
Steroids
Vecuronium
Rocuronium
Pancuronium
Pipecuronium
Which non depolarising SM relaxants are metabolised by the Liver?
Vecuronium
Rocuronium
Which non depolarising SM relaxants are metabolised by kidney filtration?
Pancuronium
Pipecuronium
Which is the longest acting non-depolarising SM relaxant?
Pancuronium
What is the duration of action of Vecuronium?
Intermediate acting
What is the duration of action of Rocuronium?
Intermediate acting (dose dependent)
What is the duration of action of Pancuronium?
Long acting
What is the duration of action of Pipecuronium?
Long acting
What are the long acting SM relaxants?
Doxacurium
Pancuronium
Pipecuronium
What are the intermediate acting SM relaxants?
Vecuronium
Rocuronium
Atracuronium
Cistracuronium
What are the short acting SM relaxants?
Mivacurium
What is the time order o the curare-induced muscle paralysis?
- Outer eye muscles
- Facial muscles
- Pharyngeal muscles
- Extremities
- Truncal muscles
- Respiratory muscles
- Full Paralysis
How long does it take to reach full paralysis?
2-6 mins
What can be used to terminate the effect of the steroid non-depolarising SM relaxants?
Sugammadex
What is the depolarising non competitive SM relaxant?
Succinylcholine
How is Succinylcholine metabolised?
Pseudocholinesterase
What is the time order of the Succinylcholine induced muscle paralysis?
- Arms
- Neck
- Legs
- Respiratory muscles
- Facial muscles
- Pharyngeal muscles