Muscle Relaxants Flashcards
What is the primary use of Neuromuscular Blockers?
adjunct to general anesthesia to relax muscles without cardiorespiratory depression
Lack CNS activity
Spasmolytic indications
Chronic Back Pain
Fibromyalgia
Muscle Spasms
“Central Acting” muscle relaxants
2 categories of Neuromuscular blockers
- Nondepolarizing agents
2. Depolarizing agents
Nondepolarizing agent mechanism
Competitive antagonist at the nAChR that blocks depolarization
Depolarizing agent mechanism
causes excess depolarization with no repolarization. Leads to flaccid paralysis
What duration of action is most preferred for the neuromuscular blocking agents?
Intermediate- 20-60m
Adverse effects of Neuromuscular blockers
Effects lasting too long Hypotension with Tachy Histamine release (bronchoconstriction, salivary secretion)
What is used to reverse NMJ blockage
AChE inhibitors
Anticholingeric co-administered to minimize mAChR overactivation
What is the most clinically relevant depolarizing agent?
Succinylcholine
Phase 1 Block of Succinylcholine
Depolarizes membrane and prevents repolarization
Phase 2 Block of Succinylcholine
membrane repolarizes but is desensitized and doesn’t depolarize, similar to nondepolarizing block. Reversed by AChE inhibitor
4 uses for NMBDs
- Surgical relaxation
- Tracheal Intubation
- Control of Ventilation
- Treatment of Convulsions
Drugs used for rapid intubation
Succinylcholine
Rocuronium
Vecuronium
Drugs used as adjuncts to anesthesia
Pancuronium
Atracurium
Cisatracurium
Spasmolytic Agents
relax spastic muscle seen in cerebral palsy, MS, and stroke. Can be centrally acting or non-centrally acting
Centrally acting spasmolytic agents
Baclofen (GABAb agonist)
Carisoprodol (unknown MOA)
Cyclobenzaprine aka Flexeril (unknown MOA)
Diazepam (Benzo)
Non-centrally acting spasmolytic agents
Dantrolene- Ryanodine receptor antagonist that inhibits Ca release from SR
Botox- inhibits ACh release
Agents for MS
Glucocorticoids (in acute attack)
Interferons- interferes with T-cell adhesion
Glatiramer Acetate- activates Tregs to save MBP
Mitoxantrone- DNA intercalating agent
Adverse effects of non depolarizing agents
Histamine release–> wheals, bronchospasm, hypotension, bronchial/salivary secretion
Drug-Drug interactions with Non-depolarizing NMBD
Aminoglycosides and some other classes of ABX
How do burn patients or those with UMN diseases react to non depolarizing NMBD?
They are resistant
How can you recognize a non depolarizing NMBD
-cur- in the name (Atracurium, Cisatracurium, Doxacurium, etc)
What are the steroid derivative muscle relaxants and why are they good?
Less Histamine release.
Vecuronium, Rocuronium, Pancuronium, Pipecuronium,
With steroids, you are Very Red & your Penis is Poppin’
What drug can be given as an alternative to Succinylcholine?
Rocuronium
Black box warning of Succinylcholine
Rhabdomyolysis with Hyperkalemia
How do you treat malignant hyperthermia?
Dantrolene
Baclofen
GABAb agonist that hyper polarizes and inhibits neurotransmitter release
Tizanidine
a2-agonist that decreases input to alpha motor neurons
Dantrolene
RyR inhibitor that stops efflux of Ca from SR in muscle
Cardiac and SM not affected
