Pharmacology of Neuromuscular Blockers Flashcards
What does Ach hydrolyze into?
Acetate and choline
What are the three skeletal muscle relaxants acting at the neuromuscular junction used in therapy?
Competitive Neuromuscular Blockers
Depolarizing Neuromuscular Blockers
Botulinum Toxin
What are two types of competitive neuromuscular blockers?
Isoquinolones
Steroid-like
What is a common direct acting muscle relaxant?
Dantrolene
What is a common depolarizing neuromuscular blocker?
Succinylcholine
What are common Isoquinolones?
Atracurium
Cisatracurium
Doxacurium
What are common steroid-like skeletal muscle relaxants?
Pancuronium
Rocuronium
Vecuronium
What are two general chemical types of competitive neuromuscular blockers?
Aliphatic chain bis-quaternaries
Steroid-like chain bis-quaternaries
How do competitive neuromuscular blocking agents work?
Competitively inhibit acetylcholine from binding to the nicotinic receptor at the neuromuscular junction
Why do isoquinolines and steroid-like drugs not work well on muscarinic receptors?
Because they have 2 positive charges and fit poorly into a ganglionic nicotinic receptor
What happens when pancuromium or rocuronium are administered?
Pupil dilation
Tachycardia
What gives cisatracurium an advantage over atracurium?
Atracurium caused release of histamine whereas cisatracurium does not so there is no inflammation
How do non-depolarizing agents work?
Competitively inhibit acetylcholine binding to nicotinic receptors at the neuromuscular junction
What drug reverses the neuromuscular blockade?
Neostigmine (anticholinesterase)
How are steroid like NM blockers excreted?
In bile and renally
What is the order of susceptibility to blockade?
Small muscles of eye -> Muscles of hand, facial muscles -> Diaphragm and vocal cords
What is the byproduct of atracurium and cisatracurium hydrolysis?
Laudosine
What happens when succinylcholine is administered?
Initially there is a repeated activation of nicotinic receptors (muscle rigidity) followed by flaccid paralysis (muscle is not sensitive to depolarization anymore)
Succinylcholine initially stimulates autonomic ganglia causing what?
Bradycardia (prevented by atropine) and cardiac arrhythmia
What can Succinylcholine cause?
Hyperkalemia: cardiac arrest/arrhythmia
How does Dantrolene work?
Binds to ryanodine (RyR1) receptors in skeletal muscle not allowing calcium to be released from SR
Why does Dantrolene not work in smooth or cardiac muscle?
They have RyR2 not RyR1
What is Dantrolene used to treat?
malignant hyperthermia
How many types are botox are approved for use?
2 type A
1 type B
