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30 Cards in this Set

  • Front
  • Back
Depolarizing Agent
binds to nicotinic receptors at NMJ

causes initial depolarization & muscle contraction
Phase I --depolarizing agent
occupies receptor longer than ACh, prevention repolarization and further depolarization
Phase II -- depolarizing agent
with time, membrane gradually repolarizes, but is desensitized since nicotinic receptors are still occupied
Phase I vs. Phase II --Depol. agen
Phase I = flaccid paralysis = can't reverse block

Phase II = neostigmine may reverse block
Succinylcholine
is a depolarizing drug
Competitive "non-depolarizing" Drugs
d-tubocurarine
pancuronium
atracurium
vercuronium
rocuronium
mivacurium --- not in U.S.
Competitive Agents
bind to nicotinic receptors @ NMJ

block in competitive manner = flaccid paralysis "Limp"

small muscles 1st > large later > diaphragm last
Malignant Hyperthermia
fast rise in body temperature + muscle contractions

due to excessive Calcium release in a genetically susceptible patient

assoc. w/ genetic mutation of autosomal dominant mutation chromosome 19
Succinylcholine -- adverse effect
malignant hyperthermia

due to excessive Calcium release in a genetically susceptible
Malignant Hyperthermia-- drug reactions
anesthetics -- malignant hyperthermia

anti-psychotics -- neuroleptic malignant syndrome
Duration of Action -- depolarizing v. competitive
Depolarizing agent = quick start, short duration

Competitive agent = slower start, longer duration
Duration of Action -- specific drug
Succinylcholine = 1 min start, 5 min duration

Pancuronium = 1.5 min start, 3 hour duration

Atracurium = 1.5 min start, 30 min duration
Baclofen
GABAa agonist

↑K+ conductance in Spinal Cord neurons
=
decrease Excitatory Neurotransmitter release
Baclofen -- clinical use
multiple sclerosis (MS) and other spasticity disorders
Diazepam
binds to benzodiazepine site on GABAa receptor

↑chloride influx in response to stimulation of receptor

= ↑↑ GABA mediated inhibition
Diazepam -- clinical uses
decrease muscle tone in muscle spasms of any cause
Dantrolene
prevents calcium release from sarcoplasmic reticulum in skeletal muscle
Dantrolene -- clinical use
prevents Excessive Ca release in genetically susceptible patients

Prevents adverse effects .....
Malignant Hyperthermia (succinylcholine )
Neuroleptic Malignant syndrome (anti-psychotics)
Cyclobenzaprine & Carisoprodol
treat acute local muscle spasm

believe to act thru brainstem to relieve muscle spasm to acute muscle injury
Depolarizing and Competitive Muscle Relaxants
treat muscle paralysis during . . .

Surgery
Mechanical Ventilation (w/ anesthetic agent)
Succinylcholine -- Adverse Effects
Excessive intracellular Calcium = malg. hyperthermia

Hyperkalemia = patients w/ damaged skeletal muscle
Pancuronium -- Adverse Effect
Cardiac Muscarinic block
Curare---Adverse Effects
Histamine release

Ganglionic Block
Atrcurium -- Adverse Effect
Histamine release
What drugs trigger histamine release?
Curare (d-turbocararine)

Atracurium
What triggers Ganglionic Block?
Curare -- competive nondepolarizing msk relaxant
Prolongs duration of Succinylcholine effects
genetic defect leading to deficient cholinesterases
Succinylcholine -- metabolism
rapidly metabolized by plasma cholinesterases
What drug's effects can be reversed by cholinesterase inhibitors?
Succinylcholine

(-) cholinesterase = (-) metabolic breakdown
Neostigmine
reversible acetylcholinesterase inhibitor

(-) ACh metabolism = more ACh = stimulates muscle

reverses Succinylcholine muscle relaxation