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Skeletal Muscle Relaxants
COMLEX
6
Pharmacology
Professional
05/28/2010

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Cards

Term
why do we need to used skeletal muscle relaxants?
Definition
to obtain a flaccid muscle field for surgery, and to prevent laryngospasm with intubation
Term
what are the two classes of drugs used as muscle relaxants?
Definition

non-depolarizing agents that block the Ach binding site

*atracurium

*mivacurium

 

depolarizing agents that send the muscle into contraction and desensitize them

*succinylcholine

Term
describe the MOA, side effects, and uses for atracurium and mivacurium
Definition

these bind the alpha-site on the Nm receptor found on skeletal muscle, blocking depolarization of the muscle

 

they competitively inhibit Ach binding

 

they have NO EFFECT of CNS, cardiac or smooth muscle

 

atracurium is safe in renal and hepatic impairment, but it is spontaneously metabolized into laudanosine, which can cause seizures once off the drug. CI in pts w Hx of seizure

mivacurium is metabolized by plasma cholinesterase, so slow metabolizers will have longer effect of drug

 

toxicity or effect of these drugs can be reveresed with AchE inhibitors (neostigmine)

Term
describe the moa, side effects, and clinical uses for succinylcholine
Definition

is a depolarizing/noncompetitive nicotinic agonist

 

initially stimulates (phase I)contraction, so will see fasciculations then moves into (phase II) desensitization

 

caution: some pts have abnormal ryanodine receptor that lets out way too much Ca2+ with the initial contraction induced by succinylcholine, which can send the pt into -> malignant hyperthermia (50% of pts who suffer this rxn have the mut ryanodine gene)

some patients will be slow metabolizers with atypical pseudocholinesterases, and will have increased effect and duration

 

hyperkalemia can increase the effect of the drug as well

Term
besides acting on the skeletal muscles themselves, what's another way to achieve muscle relaxation?
Definition

centrally!!

 

can use benzo's through GABAa receptors, etc

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