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47 Cards in this Set
- Front
- Back
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What are neuromuscular blocking agents (NMBA)used for?
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--Relax skeletal muscle for surgical procedures and tracheal intubation
--prevent fractures and dislocations associated with ECT --Control of muscle spasms of tetanus --Sustained NM blockade in critically ill patients |
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What are the non-depolarizing (competitive antagonists) isoquinoline derivative agents?
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Tubocurarine
Atracurium Cistracurium Mivacurium |
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What are the non-depolarizing (competitive antagonsits) steroid derivative agents?
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Pancuronium
Vercuronium |
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What is the depolarizing (agonist) agent?
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Succinylcholine
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What are the muscle relaxant agents used for?
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Provide relief of spasticity associated with cerebral palsy, MS, spinal cord lesions, head trauma, etc.
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What are the muscle relaxant agents?
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Baclofen
Diazepam Dantrolene |
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What does the NMBA have a structural relationship to?
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ACh
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NMBA have...
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at least one quaternary N (charged)
All are highly polar and are inactive orally |
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NMBA Tubocurarine...
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--non-depolarizing blocker
--Quarternary N --Competitive antagonist to ACh at NMJ (nicotinic)--skeletal muscle endplates --Autonomic ganglia (adrenal medulla (Nn) --Little or no effect on muscarinics |
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NMBA Tubocurarine...
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--no effect on excitability or conduction of nerve or muscle
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Flaccid paralysis of muscles goes in what order?
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Smaller rapid muscles first and progress to larger slow moving muscles:
eyes face limbs abdominal intercostals diaphragm Function is recovered in reverse order |
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Why do you see hypotensive effects in Tubocurarine?
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Due to ganglia/adrenal effect and histamine release
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What are the adverse effects of Tubocurarine?
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Hypotension
Reflex tachycardia Respiratory paralysis Bronchospasm (esp. in asthmatics) |
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What is the onset of action of Tubocurarine?
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5 minutes and duration ~ 90 minutes
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What reverses effects of NMBA?
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AChE such as neostigmine
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NMBA Tubocurarine...
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Doesn't cross BBB and is eliminated extensively by kidneys
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NMBA Tubocurarine have interactions with...
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--Several drugs have some NMB effects that augment those of NMB agents--some anesthetics and antibiotics
--Low K potentiates and high K opposes --Newborns, aged, and myasthenics are sensitive |
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NMBA Succinylcholine Duration
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~ 5 minutes
Elimination--plasma cholinesterase |
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NMBA Mivacurium Duration
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~ 10-20 minutes
Elimination--plasma cholinesterase |
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NMBA Atracurium Duration
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~ 30-60 minutes
Elimination--Spontaneous and plasma cholinesterase |
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NMBA Cistracurium Duration
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~30-60 minutes
Elimination--Mostly spontaneous |
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NMBA Vecuronium Duration
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~60-90 minutes
Elimination--Liver metabolism |
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NMBA Tubocurarine Duration
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~80-120 minutes
Elimination--Renal |
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NMBA Pancuronium Duration
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~120-180 minutes
Elimination--Renal |
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Depolarizing NMJ Blockers Succinylcholine...
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--Depolarizing agonist
--short acting --produces initial depolarization...then block --muscle fasiculations may be seen |
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Depolarizing NMJ Blockers Succinylcholine...
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--Phase 1-depolarizatio like that of ACh but longer
--non-reversible by AChE inhibitors --Phase II-with high dose or continuous exposure (desensitization) |
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Depolarizing NMJ Blockers Succinylcholine...
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--Stimulates histamine release (< tubo but > than pancuronium)
--hyperkalemia can be extensive (denervation)--can be life threatening in certain patients, be careful in CHF on dig or diuretics --use on short term procedures |
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Depolarizing NMJ Blockers Succinylcholine...
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--AChE agents may increase blockade
--Rapidly metabolized by plasma and liver pseudocholinesterase --Bradycardia --Post-op muscle pain |
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What causes malignant hyperthermia (MH)?
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--Genetic disorder of skeletal muscle
--One of main causes of death due to anesthesia --Triggered by anesthetics or succs |
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What do you see in MH?
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--Rapid hyperthermia and metabolic acidosis
--tachycardia --accelerated muscle metabolism and contractures --potentially fatal |
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How do you treat MH?
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Symptomatically and with Dantrolene
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Why is muscle relaxants used?
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--Spasticity d/t loss of supraspinal control over spinal cord reflexes-results in "hyperreflexia" of spinal refexes
--spasticity with MS, CP, etc. --used to reduce hyperactive reflex by decreasing activity of Ia fibers or enhancing of internuncial inhibitory neurons |
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What is Baclofen?
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--Skeletal muscle relaxant
--GABA analog acts on GABAb pre and post synaptic receptors --increased K conductance, decreased calcium influx --decreased excitatory NT release, decreased motor neuron activity --effective as diazepam with less sedation and little effect on muscle strength (unlike dantrolene) |
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What are the side effects of Baclofen?
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--graduated doses minimizes
--drowsiness and dizziness --hypotension (OD) --elderly/MS--more senstive and need smaller doses --abrupt withdrawal potentiate increases spasm --sometimes given via infusion pump |
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What is the agent of choice for spinal spasticity?
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Baclofen
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What is diazepam?
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--Skeletal muscle relaxants
--anxiolytic agent (benzodiazepine) --acts at all GABAA synapses but reduces spasticity partly at spinal cord level --Not a GABA agonist but enhances GABA effect |
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What is the primary problem with Diazepam?
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Sedation
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What type of metabolism does diazepam have?
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Complex hepatic
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Does tolerance develop with diazepam?
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Yes, both therapeutic as well as side-effects
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What is diazepam used to control?
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Flexor and extensor spasms, spinal spasticity and MS as well as treat anxiety D/O
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What drugs are used to treat signs and symptoms of localized muscle spasm?
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--Analgesic-antiinflammatory
--most are sedative and muscle relaxant properties may be partly a result of sedatoin (Drowsiness a common side effect) |
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What is the most popular drug for localized muscle spasm?
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cxyclobenzaprine (Flexeril)--has significant anticholinergic side effects
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What are other agents used to treat localized muscls spasm?
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Carispoprodol
Chlorzoxazone Metaxalone Methocarbamol Orphenadrine Tizanidine Cyclobenzaprine |
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What is a peripheral acting skeletal muscle relaxant?
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Dantrolene
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How does dantrolene work?
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Acts at level of muscle --> inhibits calcium release form SR and uncouples excitation-contraction --> doesnt alter membrane contraction
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What is the biggest problem with dantrolene?
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Dose-dependent muscle weakness is biggest
--diarrhea --hepatotoxicity (rare) |
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What is dantrolene used for?
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MS
CP Spinal cord lesions DOC for MH |
