Neuromuscular Agents

Question 1

Types of nicotinic receptors

Answer 1

Nn: CNS excitation
Ng: autonomic ganglia –> ganglionic transmission
Nm: skeletal muscle contraction

Question 2

What are the nondepolarizing NM blockers?

Answer 2

Isoquinolones:
-atracurium
-cisatracurium
-doxacurium
Steroid-like
-Pancuronium
-Rocuronium
-Vecuronium

Question 3

What are the depolarizing NM blockers?

Answer 3

succinylcholine

Question 4

What isoquinolone is no longer used?

Answer 4

Tubocurarine

Question 5

Describe the onset, elimination, and clearance of isoquinolones

Answer 5

Onset: faster in younger patients
Elimination: spontaneous hydrolysis (atracurium and cisatracurium; temperature & pH dependent process
Clearance: 5-6 mL/kg/min

Question 6

List the isoquinolones in order of potency and duration of action (highest to lowest)

Answer 6

Doxacurium
Cisatracurium
Atracurium

Question 7

What are the indications of isoquinolones?

Answer 7

• skeletal muscle relaxation or mechanical ventilation during surgery
• endotracheal intubation

Question 8

What is the reversal agent for isoquinolones?

Answer 8

Neostigmine with atropine

-increases ACh which stimulates nerve and mAChR

Question 9

What are the adverse reaction of isoquinolones?

Answer 9

• dose dependent histamine release
• cutaneous flushing, hypotension
• CV effects (tachycardia)
• seizures wit atracurium
• Laudanosine (metabolite from cisatracurium)

Question 10

Describe the elimination and clearance of steroid-like blockers

Answer 10

elimination: kidneys (pancuronium) and liver (rocuronium & vecuronium)
clearance: 1.7-5.3 mL/kg/min

Question 11

What are the indications for steroid-like blockers?

Answer 11

• skeletal muscle relaxation or mechanical ventilation during surgery
• endotracheal intubation
• euthanasia (pancuronium/rocuronium)

Question 12

What are the adverse effects of using steroid-like blockers?

Answer 12

• sinus tachycardia (pancuronium > rocuronium)
• hypotension
• at high doses – relaxed diaphragm mediated asphyxiation

Question 13

What is the reversal agent for rocuronium and vecuronium?

Answer 13

neostigmine

• increase ACh –> stimulate nerve and nAChR
• 17 min reversal time

Question 14

Describe Sugammadex

Answer 14

• used to reverse rocuronium (then vecuronium and pancuronium)
• rapid, so 1st selective relaxant binding agent (SRBA)
• doesn’t inhibit AChE
• inactivates rocuronium by wrapping around it
• expensive

Question 15

What is the mode of action for succinylcholine?

Answer 15

repeated activation of nAChRs –> increased depolarization = paralysis

Question 16

Describe the elimination and clearance of succinylcholine

Answer 16

elimination: plasma ChE
clearance: >100 mL/kg/min

Question 17

What are the indications for succinylcholine?

Answer 17

• S/T paralysis as part of general anesthesia

- tracheal intubation

Question 18

What are the adverse side effects of succinylcholine?

Answer 18

• sinus bradycardia
• malignant hyperthermia & allergic reactions
• hyperkalemia – efflux of K+ into extracellular space from large muscle groups

Question 19

What is the reversal agent for succinylcholine?

Answer 19

none!

Question 20

Describe the duration of action, elimination, and resistance to succinylcholine

Answer 20

DOA: <8 mins

elimination: via plasma ChE
resistance: associated with obesity

Question 21

What are the black box warnings for succinylcholine?

Answer 21

• muscular dystrophy
• cardiac dysfunction
• pseudocholinesterase deficiency
• metabolic acidosis
• myasthenia gravis
• can only be used on children under 8 yo for intubation

Question 22

Describe Dantrolene

Answer 22

• direct acting muscle relaxant
• binds RyR1 receptors = reduced Ca2+ release
• malignant hyperthermia

Question 23

Describe Botulinum toxin

Answer 23

• blocks release of ACh from vesicles at NMJ = paralysis of SM
• Toxins A and B

Question 24

What are the indications for botulinum toxin in adults?

Answer 24

• incontinence w/ overactive bladder
• prevent headaches w/ chronic migraines
• muscle stiffness w/ upper limb spasticity
• cervical dystonia
• hyperhidrosis
• improve moderate to severe frown lines
• improve crow’s feet lines

Question 25

What are the indications for botulinum toxin in children 12 yo +?

Answer 25

-strabismus or blepharospasm associated w/ dystonia

Question 26

What are the adverse reactions associated with botulinum toxin?

Answer 26

• visual disturbances (most sensitive)
• headache
• difficulty breathing
• light sensitivity
• allergy
• double vision
• urinary retention