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MSK Pharmacology 4 & 5 (Skeletal Muscle Relaxants) Flashcards

GOOOAL: To understand how to manage spasticity and spasms in patients with upper and lower motor neuron lesions, respectively. (82 cards)

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1
Q

two classes of skeletal muscle relaxants

A

neuromuscular blocking drugs and skeletal muscle spasmolytic drugs

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2
Q

uses of neuromuscular blocking drugs

A

to produce muscle paralysis in order to facilitate surgery or artificial ventilation

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3
Q

purpose of spasmolytic drugs

A

to reduce abnormally elevated muscle tone (spasticity) without paralysis (e.g. baclofen, dantrolene, etc.)

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4
Q

definition of spasm

A

sudden, violent, painful, and involuntary contractions of a muscle or group of muscles (i.e. cramps)

involves motor neurons (balance between musculoskeletal movement and body posture)

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5
Q

relation of action potentials to neuromuscular junctions (NMJs)

A

action potentials by motor neurons are conducted directly to nerve terminals in muscle fibers that form synapses called neuromuscular junctions (NMJs)

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6
Q

______ is released from the nerve terminal, stimulating ______ receptors on the muscle to produce contraction

A

acetylcholine, nicotinic receptors

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7
Q

spasticity

A

an increase in the passive stretch resistance of a muscle or muscle group

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8
Q

physical manifestation of spasticity

A

stiff and awkward movements due to increased muscle tone or contractions

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9
Q

duration of spasticity

A

permanent condition and may progress to disabling condition without therapy

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10
Q

common causes of spasticity

A

closed head injuries
cerebral palsy
multiple sclerosis
stroke

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11
Q

mediator of spasm

A

lower motor neurons (LMNs)

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12
Q

mediator of spasticity

A

upper motor neurons (UMNs)

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13
Q

typical causes of spasm

A 
bursitis
dislocation
fracture
epilepsy
herniated disc
hypocalcemia
myositis
neuritis
strains
"whiplash" injuries
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14
Q

typical causes of spasticity

A 
cerebrovascular accident
closed head injury
hemiplegia
paraplegia
quadriplegia
multiple sclerosis
poliomyelitis
spinal cord trauma
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15
Q

Where do neuromuscular blockers work?

A

interfere with transmission at the neuromuscular end plate and are NOT centrally acting drugs (e.g. atracurium, pancuronium, gallamine)

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16
Q

Where do spasmolytics work?

A

they been traditionally called “centrally acting” muscle relaxants but one member, dantrolene is peripherally acting and has no significant central effects (e.g. baclofen, diazepam, tizanidine)

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17
Q

baclofen (Lioresal)

A

centrally-acting drug used to treat spasticity

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18
Q

botulinum toxin type A (Botox)

A

centrally-acting drug used to treat spasticity

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19
Q

diazepam (Valium)

A

centrally-acting drug used to treat spasticity

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20
Q

tizanidine (Zanaflex)

A

centrally-acting drug used to treat spasticity

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21
Q

dantrolene (Dantrium)

A

PERIPHERALLY-acting drug used to treat spasticity

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22
Q

How does baclofen work?

A

acts within the spinal cord to suppress hyperactive relfexes involved in regulation of muscle movement

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23
Q

baclofen is the structural analogue of _____

A

GABA (mimics the actions of GABA on spinal neurons)

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24
Q

For which receptor is baclofen selective?

A

GABA B (B for baclofen!)

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25
Dr. Ngu's take home message about the action of baclofen
acts at the level of the spinal cord to restore inhibiting tone
26
therapeutic use of baclofen
to reduce spasticity associated with MS, spinal cord injury, and cerebral palsy
27
For which two condition is baclofen NOT effective?
stroke and Parkinson's
28
therapeutic effect of baclofen
decreases flexor and extensor spasms and suppresses resistance to passive movement (reduction of the discomfort of spasticity and allowing increased performance)
29
Preferred treatment for patients whose spasticity is associated with significant muscle weakness?
baclofen instead of dantrolene
30
absorption of baclofen
generally good
31
time to peak concentration of baclofen
2-3 hrs.
32
onset of action of baclofen
variable (hours to days)
33
half life of baclofen
2.5-4 hrs.
34
location of baclofen metabolism
liver
35
location of baclofen excretion
kidneys
36
Side effects of baclofen are most associated with which body systems?
CNS and GI tract (serious adverse effects are rare)
37
effects of baclofen on the CNS
CNS depressant frequently causes drowsiness, dizziness, weakness, and fatigue (most intense during the early phase of therapy and diminish with continued drug use)
38
baclofen contraindications
patients should not use alcohol or other CNS depressants because baclofen potentiates the depressant action of these drugs
39
family to which diazepam belongs
benzodiazepine family
40
only benzodiazepine labeled for treating spasticity
diazepam
41
How does diazepam act?
acts within the CNS by facilitating GABA-mediated presynaptic inhibition (mimics GABA A at receptors in the spinal cord and brain)
42
use of diazepam
in patients with muscle spasm of almost any origin, including local muscle trauma
43
side effect of diazepam
sedation (occurs in most patients at the doses required to significantly reduce muscle tone)-- minimized by initiating therapy with low doses
44
Preferred drug in patients with marginal strength?
diazepam over dantrolene
45
drugs that interact with baclofen
alcohol antihistamines CNS depressants MAO inhibitors
46
drug interaction effects with baclofen
increased CNS depression, increased risk of hepatotoxicity with combination of chlorzoxazone and alcohol
47
drugs that interact with chlorphenesin (antifungal, antibacterial)
tricyclic antidepressants (e.g. amitriptyline)
48
effects of drug interactions with chlorphenesin
inc. CNS depression, inc. risk of hepatotoxicity with combo of chlorzoxazone and alcohol
49
location of dantrolene action
peripheral (directly on skeletal muscle itself)
50
primary action of dantrolene
suppression of calcium release from the sarcoplasmic reticulum (decreases the ability of skeletal muscle to contract)
51
therapeutic advantage of dantrolene
minimal effects on smooth muscle and cardiac muscle
52
therapeutic uses of dantrolene
1. spasticity (MS, cerebral palsy, spinal cord injury) | 2. malignant hyperthermia
53
side effect of dantrolene
may be associated w/ a significant decrease in strength (generalized reduction in ability of skeletal muscle to contract)
54
malignant hyperthermia
life-threatening syndrome that can be triggered by any general anesthetic and by succinylcholine, a neuromuscular blocking agent
55
prominent symptoms of malignant hyperthermia
muscle rigidity, profound elevation of temp. (heat is generated by muscle contraction secondary to massive release of calcium from the SR)
56
How does dantrolene treat malignant hyperthermia?
acts on the SR to block calcium release
57
most serious toxic effect of dantrolene
dose related liver damage liver damage has incidence of 1 in 1,000 death from extensive liver damage has occurred
58
What should be performed prior to and throughout treatment with dantrolene?
tests of liver function
59
adverse toxic effects of dantrolene
``` drowsiness dizziness malaise lightheadedness insomnia fatigue confusion increased urinary frequency ```
60
dantrolene drug interactions causing increased toxicity
estrogen (hepatotoxicity) CNS depressants (sedation) clindamycin (increased neuromuscular blockade) verapamil (hyperkalemia and cardiac depression) warfarin clofibrate tolbutamine
61
carisoprodol (Soma, Vanadom)
centrally-acting drug for acute local muscle spasm (LMNs) | can be addictive
62
chlorphenesin (Maolate)
antifungal, antibiotic | centrally-acting drug for acute local muscle spasm (LMNs)
63
chlorzoxazone (Paraflex, Relaxone)
centrally-acting drug for acute local muscle spasm (LMNs)
64
cyclobenzaprine (Cycloflex, Felexeril)
centrally-acting drug for acute local muscle spasm (LMNs) | injury-related spasms
65
diazepam (Valium)
centrally-acting drug for acute local muscle spasm (LMNs AND UMNs)
66
metaxalone (Skelaxin)
centrally-acting drug for acute local muscle spasm (LMNs)
67
methocarbamol (Carbacol, Robaxin, Skelex)
centrally-acting drug for acute local muscle spasm (LMNs) | high risk in the elderly, can slow HR, cause itchy skin rash and sedation
68
vigabatrin (Sabril)
centrally-acting drug for acute local muscle spasm (LMNs) | GABA transaminase inhibitor
69
laundry list of centrally-acting drugs for acute local spasms (LMNs)
Carisoprodol (Soma, Vanadom) Chlorphenesin (Maolate), (anti fungal & anti biotic) Chlorzoxazone (Paraflex, Relaxone) Cyclobenzaprine (Cycloflex, Flexeril) (injury-related spasms) Diazepam (Valium) Metaxalone (Skelaxin) (strains, sprains) Methocarbamol (Carbacol, Robaxin, Skelex) (high risk in elderly) Vigabatrin (Sabril) – a GABA transaminase inhibitor
70
another laundry list of drugs used for acute local muscle spasm
Chlorphenesin (contraindicated during pregnancy) Chlorzoxazone Metaxalone Methocarbamol Orphenadrine (anticholinergic properties) Carisoprodol Cyclobenzaprine
71
Drugs used for acute local muscle spasm are promoted for...
...the relief of acute temporary muscle spasm caused by local trauma or strain. (yes, this is redundant) Most act as a sedative or at the level of the spinal cord or brain stem.
72
Which drug is the prototype of the group of drugs used for acute local muscle spasm?
cyclobenzaprine (believed to act at the level of the brain stem; has some muscarinic effects such as contraction of the detrusor muscle by the bladder)
73
For which conditions is cyclobenzaprine ineffective in treating muscle spasm?
cerebral palsy and spinal cord injury
74
cyclobenzaprine's protein binding and why it's significant
93%, very high, has the ability to interact with other drugs
75
dantrolene's protein binding and why it's significant
90%, very high, ability to interact with other drugs
76
effects of orphenadril
inhibits H1 receptors (antihistamine), inhibits muscarinic receptors (anticholinergic), inhibits NMDA receptors in CNS, inhibits norepinephrine reuptake (the drug has many uses including treatment of fibromyalgia)
77
baclofen contraindication
skeletal muscle spasms caused by rheumatoid arthritis
78
carisoprodol contraindication
patients with known hypersensitivity to meprobamate
79
cyclobenzaprine contraindication
MI, cardiac conduction disorders, hyperthyroidism
80
dantrolene contraindication
active hepatic disease, muscle spasms caused by rheumatoid arthritis
81
tixanidine
alpha2 agonist | hypotension, drowsiness, dry mouth
82
botulinum toxin
spasticity from cerebral palsy | cosmetics surgery

Pharmacology (1 decks)

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