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MSK Pharm > Smooth m relaxants--Agents that act on the NMJ > Flashcards

Smooth m relaxants--Agents that act on the NMJ Flashcards

1
Q

Neuromuscular blocking drugs

A

Nondepolarizing- Isoquinoline derivatives, Steroid derivatives
-Depolarizing- Succinylcholine

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2
Q

Isoquinoline derivatives

A

-Atracurium
-Cisatracurium
-Doxacurium
-Metocurine
-Mivacurium
-Tubocurarine
CURIUM

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3
Q

Steroid derivatives

A

-Pancuronium
-Pipercuronium
-Rocuronium
-Vecuronium
CURONIUM- PPRV

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4
Q

M relaxants (spasmolytics)

A
  • Dantrolene

- Botulinum toxin

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5
Q

Acetycholinesterase inhibitors

A
  • Ambeonium
  • Donepezil
  • Echothiophate
  • Edrophonium
  • Galantamine
  • Neostigmine
  • Physostigmine
  • Pyridostigmine
  • Rivastigmine
  • Tacrine
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6
Q

Antimuscarinic compounds

A
  • atropine

- glycopyrrolate

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7
Q

Cholinesterase reactivators

A

-Pralidoxime

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8
Q

neuromuscular blocking drugs- 2 mech’s

A
  • Nondepoliarizing- antagonists at nAChR (d-tubocurarine- prototype)
  • Depolarizing- excess of a depolarizing agonist (prototype- succinylcholine)
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9
Q

Nondepolarizing neuromuscular blocking agents- moa, pharmacodynamics

A
  • competitive antagonist at nAChR
  • large doses- can enter the pore of nAChR- diminish the ability of ACHase inhibitors to antagonist their effects
  • larger m’s- more resistant to blockade and recover more rapidly (diaphragm- last m to be paralyzed, quickest to recover)
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10
Q

Reversal of neuromuscular blockade

A
  • ACH (nAChR agonist) or succinylcholine (rarely used)
  • Neostigmine and pyridostigmine (cholinesterase inhibitors)- inc availability of ACH at motor end plate AND inc release of NT from motor n terminal
  • Edrophonium- purely a cholinesterase inhibitor
  • Anticholinergic agents (coadmin w cholinesterase inhibitors)- minimize adverse cholinergic effects
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11
Q

Nondepolarizing agents- adverse effects

A
  • produce histamine release- wheals, bronchospasm, hypotension, bronchial and salivary secretion
  • at large doses- hypotension and tachycardia
  • d-tubocurarine causes significant histamine release; very long duration of action- not used as much clinically
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12
Q

Nondepolarizing agents- drug-drug interactions

A
  • Anesthetics- (inhaled)- potentiate the neuromuscular blockade - Isoflurane&raquo_space; sevoflurane = desflurane = enflurane = halothane > NO
  • aminoglycosides enhance blockade; some reduce the release of ACH in prejunctonal neuron
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13
Q

Nondepolarizing agents- effects of dz and aging on neuromuscular response

A
  • prolonged duration of action- in elderly pts w reduced hepatic and renal fxn
  • enhanced in pts w MG
  • severe burns and UMN dz- resistant to nondepolarizing agents!!
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14
Q

Atracurium

A
  • intermediate-acting
  • inact by Hofmann elimination
  • breakdown products- Laudanosine
  • Laudanosine- slowly metabolized in liver- crosses BBB- can cause seizures- only a problem for pts w prolonged infusions of atracurium!!!
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15
Q

Neuromuscular blockers- short duration of action

A
  • Mivacurium

- Succinylcholine!!

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16
Q

Neuromuscular blockers- intermediate duration of action

A

-atracurium
-cisatracurium
-rocuronium
-vecuronium
(ACRV)

17
Q

Neuromuscular blockers- long duration of action

A

-Doxacurium
-Pancuronium
-Pipecuronium
(DPP)

18
Q

Mivacurium

A
  • shortest duration of action; onset of action is slower than succinylcholine
  • larger dose used to speed onset- assoc w profound histamine release and CV effects
  • metabolism by plasma cholinesterase (pts w renal failure have dec levels)
19
Q

Steroid derivatives

A

-intermediate-acting (vecuronium, rocuronium) - hepatic metabolism- more likely to be used clinically than long-acting (pancuronium, pipecuronium)

20
Q

Steroid derivatives- metabolites

A
  • 3-hydroxy metabolites
  • if a pt has given a steroidal nondepolarizing agent for several days in a ICU setting, the 3-hydroxy metabolite can cause prolonged paralysis b/c it has a longer half-life
21
Q

Rocuronium

A
  • most rapid time of onset, intermediate duration, lower potency
  • rapid onset- used as an alternative to succinylcholine in rapid-induction anesthesia and in relaxing the laryngeal and jaw m’s to facilitate tracheal intubation
22
Q

Succinylcholine- pharcokinetics

A
  • only depolarizing blocking drug!!
  • ultra-short duration of action
  • plasma cholinesterase hydrolyzes succinylcholine- onal a small percentage of dose reaches the NMJ
  • pts with genetically abnormal variant of plasma cholinesterase- can have prolonged blockade!!
23
Q

Succinylcholine- phases

A
  • phase I block (depolarizing)- depolarization of motor end plate spreads to adj membranes causing m contraction- m’s remain depolarized, unresponsive to subsequent impulses- flaccid paralysis occurs; augmented by cholinesterase inhibitors
  • phase II block (desensitizing)- continued exposure to succinylcholine causes the initial end plate depolarization to dec and memb becomes repolarized- memb is unable to be depolarized b/c the R is desensitized; reversed by acetylcholinesterase inhibitors
24
Q

Succinylcholine- effects

A
  • transient m twitches over chest and abdomen (30 s)
  • paralysis (<90s) in arm, neck, leg m’s, followed by resp m’s
  • used for rapid sequence induction (secure airway rapidly), and for quick surgical procedures
25
Q

succinylcholine- reversal

A

-plasma cholinesterases

26
Q

succinylcholine- adverse effects

A

CV
-cardiac arrhythmias- when admin during halothane anesthesia
-negative inotropic and chronotropic effects- can be attenuated by admin of an anticholinergic drug
-large doses can have + inotropic and chronotropic effects
Hyperkalemia- in pts w burns, n damage, or neuromuscular dz, closed head injury- release K into blood- can cause cardiac arrest
inc intraocular P
inc intragastric P
m pain
slight histamine release

27
Q

succinylcholine- contraindications

A
  • malignant hyperthermia hx
  • myopathies assoc w elevated CPK
  • acute phase of injury after major burns, mult trauma, extensive denervation of skeletal m or UMN injury
  • black box warning- cardiac arrest risk!!!- after admin to healthy children w an undiagnosed skeletal m myopathy!!
28
Q

succinylcholine- drug-drug interactions

A
  • Anesthetics- can cause malignant hyperthermia
  • Antibiotics
  • local anesthetics and antiarrhythmic drugs (minor)
29
Q

neuromuscular blocking drugs- uses

A
  • surgical relaxation
  • tracheal intubation
  • control of ventilation- in pts who have ventilatory failure; neuromuscular blockind rugs reduce chest wall resistance and improve thoracic compliance
  • tx of convulsions
30
Q

Spasmolytic agents- drugs

A
  • dantrolene

- botulinum toxin

31
Q

Dantrolene- moa

A
  • causes inhibition of RyR (ryanodine R) Ca channel- blocks release of Ca thru the SR and m contraction is impaired
  • cardiac and smooth m are unaffected (diff RyR subtype)
  • SEs- m weakness, sedation, hepatitis
32
Q

Dantrolene- used for?

A
  • tx spasticity assoc w UPMN disorders

- malignant hyperthermia!!!!!

33
Q

Botulinum toxin- moa

A
  • cleaves the SNARE complex and blocks release of ACh by preventing vesicle exocytosis
  • tx- generalized spastic disorders

MSK Pharm (10 decks)

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