Neuromuscular Blockers and Spasmolytics

Question 1

• MOA of Succinylcholine?
• Complications?

Answer 1

• MOA:
  
  • Strong AChR agonist
    
    • sustained depolarization prevents muscle contraction
    • produces muscles relaxation
    • for surgery or breathing on a ventilator
• Complications:
  
  • Hypercalcemia
  • Hyperkalemia (K+)
  • Malignant hyperthermia

Question 2

• How do you reverse the blockade of Succinylcholine?
  
  • Phases?

Answer 2

• Phase I: (prolonged depolarization)- no antidote
  
  • block potentiated by cholinesterase inhibitor
• Phase II:
  
  • repolarized but blocked, AChR are available but desensitized
    
    • may be reversed with cholinesterase inhibitors

Question 3

• What is the MOA of nondepolarizing neuromuscular blocking drugs?
  
  • all end in?
  • reversal of blockade?

Answer 3

• - curium or - curonium
  
  • Tubocurarine, atracurium, mivacurium, pancuronium, vecuronium, rocuronium
• MOA:
  
  • competitive antagonists; compete with ACh for receptors
    
    • muscle relaxant
• Reversal of blockade:
  
  • neostigmine
    
    • must be given with atropine to prevent muscarinic effects such as bradycardia
    • edrophonium
    • other cholinesterase inhibitors

Question 4

What are 5 Spasmolytics (muscle relaxant) drugs?

Answer 4

1. Dantrolene
2. Baclofen
3. Cyclobenzaprine
4. Diazopram
5. Botox (Botulinin)

Question 5

MOA of Dantrolene?

Answer 5

Prevents release of Ca2+ from the sarcoplasmic reticulum of skeletal muscle by binding to the ryanodine receptor

Question 6

• MOA of Baclofen?
  
  • used for?

Answer 6

• MOA:
  
  • Activates GABABreceptors at the spinal cord level, inducing skeletal muscle relaxation
    
    • ​GABA agonist
• Used for:
  
  • ​muscle spasms (e.g. acute low back pain)

Question 7

• Cyclobenzaprine
  
  • MOA
  • Used for

Answer 7

• MOA:
  
  • centrally acting skeletal muscle relaxant
  • structurally related to TCAs (tricyclic antidepressent)
    
    • similar anticholinergic side effect
• Used for:
  
  • muscle spasms

Question 8

• MOA of Diazepam?
• Used for?
• Side effects?

Answer 8

• MOA:
  
  • Positive allosteric modulators of GABA_A receptors
    
    • Binding of benzodiazepines to this receptor complex promotes binding of GABA, which in turn increases the total conduction of chloride ions across the neuronal cell membrane.
    • hyperpolarization; decrease neuronal firing
• Used for:
  
  • anxiety
  • spasticity
• Side effects:
  
  • sedation
  • tolerance and dependence
  • respiratory depression

Question 9

• MOA of Botulinum toxin?
  
  • causes?

Answer 9

• MOA:
  
  • protease that cleave SNARE proteins required for NT release via vesicular fusion
    
    • prevent release of stimulatory (ACh) signals at neuromuscular junction
• Causes:
  
  • flaccid paralysis
    
    • for spasmolytic