NMJ blockers Flashcards

1
Q

Atracurium (Tracrium®)

A

non-depolarizing NMJ blocker
Benzylisoquinolines
Time to onset of action 2-4 min
-degraded by temp/pH-dependent Hofmann reaction.
-not metabolized by enzymes and may be useful for patients with liver and/or renal failure.

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2
Q

Mivacurium (Mivacron®)

A

non-depolarizing NMJ blocker
Short duration of action (12-18 min)
Benzylisoquinoline, Time to onset of action: 2-4 min
metabolized by plasma
cholinesterase (why short duration)

-Problems if given when decreased plasma cholinesterase activity
Pts with liver disease or nutritional deficiencies may have abnormal plasma cholinesterase activity. Flushing of the face and neck is common.

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3
Q

Rocuronium (Zemuron®)

A

non-depolarizing NMJ blocker
Intermediate Duration of action (30-60 min)
Steroidal structure, Liver metabolism
Time to onset of action: very rapid (1-2 min) similar to succinylcholine and used to rapidly relax laryngeal and jaw muscles for tracheal intubation

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4
Q

Succinylcholine (Anectine®)

A

depolarizing NMJ blocker
Duration (5-8 min); Time to onset; 1-1.5 min – very fast
*Used for very short procedures (e.g. intubation)
*initial fasciculations mostly in the chest and abdomen,
occur immediately after drug admin
-no antidote, (like non-depol NMJ blockers)

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5
Q

NMJ blocker uses

A

GA adjuncts in sx: Cause the complete relaxation of skeletal muscle
-no CNS effects; only given IV

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6
Q

1st muscles to be blocked/affected ??

A

small rapid moving muscles → limb trunk muscles → intercostal muscles → lastly, the diaphragm
*recovery in reverse order, diaphragm is 1st to regain function

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7
Q

Botox is used to treat ??

A

blephorospasm (involuntary eyelid closing), strabismus (eye spasms) and wrinkle treatment

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8
Q

Non-depolarizing (competitive) NMJ blockers characteristics

A

Not metabolized by AChE

  • Competitive inhibitors of ACh binding to ACh receptor at NMJ
  • antiAChE agents (e.g. neostigmine) reverse NMJ block by non-depolarizing NMJ blockers
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9
Q

general non-depolarizing (competitive) NMJ blocker SEs

A

Prolonged apnea, histamine release (bronchospasm, hypotension)

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10
Q

Benzylisoquinonlines ( “___curium” name) SEs

A

Histamine release, few vagal/ganglionic blocking effects

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11
Q

Steroidal compounds (“___curonium” name) SEs

A
  • Block of ganglionic muscarinic receptors can occur resulting in tachycardia due to effects on vagus
  • Vecuronium and rocuronium are newer agents with little or no associated tachycardia or histamine release
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12
Q

succinylcholine metabolism

A

Degraded by plasma choline esterase (e.g. butyrylcholinesterase)
Problems with decreased butyrylcholineesterase: atypical or deficient plasma cholinesterase, hepatic or liver disease, nutritional deficiencies

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13
Q

succinylcholine MOA

A

alters electro-chemical driving forces: excessive opening of nicotinic ACh receptors by SCh results in decreased electro- chemical driving forces and therefore less positive ion entry in presence of ACh resulting in less muscle response to motor neuron activity.
-this is phase I: single dose, fast onset; neostigmine augments blocking action of SCh

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14
Q

Phase II SCh

A

after prolonged infusion or dosing 10X of normal dose (5 mg/kg); slow onset

  • MP: -80mV
  • Neostigmine antagonizes SCh block
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15
Q

botulinum toxin

A

besides wrinkles, for
blephorospasm – involuntary closing of eyelid and strabismus – deviation of eye position that cannot be overcome
MOA: prevent release of presynaptic ACh at NMJ
SEs: upregulation of post-synaptic nicotinic ACh receptors at previous injection site(s) resulting in increased wrinkles and ptosis - eyelid droop

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