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Pharmacology > MSK Pharmacology 4 & 5 (Skeletal Muscle Relaxants) > Flashcards

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.

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
Q

Dr. Ngu’s take home message about the action of baclofen

A

acts at the level of the spinal cord to restore inhibiting tone

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26
Q

therapeutic use of baclofen

A

to reduce spasticity associated with MS, spinal cord injury, and cerebral palsy

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27
Q

For which two condition is baclofen NOT effective?

A

stroke and Parkinson’s

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28
Q

therapeutic effect of baclofen

A

decreases flexor and extensor spasms and suppresses resistance to passive movement (reduction of the discomfort of spasticity and allowing increased performance)

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29
Q

Preferred treatment for patients whose spasticity is associated with significant muscle weakness?

A

baclofen instead of dantrolene

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30
Q

absorption of baclofen

A

generally good

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31
Q

time to peak concentration of baclofen

A

2-3 hrs.

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32
Q

onset of action of baclofen

A

variable (hours to days)

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33
Q

half life of baclofen

A

2.5-4 hrs.

34
Q

location of baclofen metabolism

A

liver

35
Q

location of baclofen excretion

A

kidneys

36
Q

Side effects of baclofen are most associated with which body systems?

A

CNS and GI tract (serious adverse effects are rare)

37
Q

effects of baclofen on the CNS

A

CNS depressant
frequently causes drowsiness, dizziness, weakness, and fatigue (most intense during the early phase of therapy and diminish with continued drug use)

38
Q

baclofen contraindications

A

patients should not use alcohol or other CNS depressants because baclofen potentiates the depressant action of these drugs

39
Q

family to which diazepam belongs

A

benzodiazepine family

40
Q

only benzodiazepine labeled for treating spasticity

A

diazepam

41
Q

How does diazepam act?

A

acts within the CNS by facilitating GABA-mediated presynaptic inhibition (mimics GABA A at receptors in the spinal cord and brain)

42
Q

use of diazepam

A

in patients with muscle spasm of almost any origin, including local muscle trauma

43
Q

side effect of diazepam

A

sedation (occurs in most patients at the doses required to significantly reduce muscle tone)– minimized by initiating therapy with low doses

44
Q

Preferred drug in patients with marginal strength?

A

diazepam over dantrolene

45
Q

drugs that interact with baclofen

A

alcohol
antihistamines
CNS depressants
MAO inhibitors

46
Q

drug interaction effects with baclofen

A

increased CNS depression, increased risk of hepatotoxicity with combination of chlorzoxazone and alcohol

47
Q

drugs that interact with chlorphenesin (antifungal, antibacterial)

A

tricyclic antidepressants (e.g. amitriptyline)

48
Q

effects of drug interactions with chlorphenesin

A

inc. CNS depression, inc. risk of hepatotoxicity with combo of chlorzoxazone and alcohol

49
Q

location of dantrolene action

A

peripheral (directly on skeletal muscle itself)

50
Q

primary action of dantrolene

A

suppression of calcium release from the sarcoplasmic reticulum (decreases the ability of skeletal muscle to contract)

51
Q

therapeutic advantage of dantrolene

A

minimal effects on smooth muscle and cardiac muscle

52
Q

therapeutic uses of dantrolene

A
  1. spasticity (MS, cerebral palsy, spinal cord injury)

2. malignant hyperthermia

53
Q

side effect of dantrolene

A

may be associated w/ a significant decrease in strength (generalized reduction in ability of skeletal muscle to contract)

54
Q

malignant hyperthermia

A

life-threatening syndrome that can be triggered by any general anesthetic and by succinylcholine, a neuromuscular blocking agent

55
Q

prominent symptoms of malignant hyperthermia

A

muscle rigidity, profound elevation of temp. (heat is generated by muscle contraction secondary to massive release of calcium from the SR)

56
Q

How does dantrolene treat malignant hyperthermia?

A

acts on the SR to block calcium release

57
Q

most serious toxic effect of dantrolene

A

dose related liver damage
liver damage has incidence of 1 in 1,000
death from extensive liver damage has occurred

58
Q

What should be performed prior to and throughout treatment with dantrolene?

A

tests of liver function

59
Q

adverse toxic effects of dantrolene

A 
drowsiness
dizziness
malaise
lightheadedness
insomnia
fatigue
confusion
increased urinary frequency
60
Q

dantrolene drug interactions causing increased toxicity

A

estrogen (hepatotoxicity)
CNS depressants (sedation)
clindamycin (increased neuromuscular blockade)
verapamil (hyperkalemia and cardiac depression)
warfarin
clofibrate
tolbutamine

61
Q

carisoprodol (Soma, Vanadom)

A

centrally-acting drug for acute local muscle spasm (LMNs)

can be addictive

62
Q

chlorphenesin (Maolate)

A

antifungal, antibiotic

centrally-acting drug for acute local muscle spasm (LMNs)

63
Q

chlorzoxazone (Paraflex, Relaxone)

A

centrally-acting drug for acute local muscle spasm (LMNs)

64
Q

cyclobenzaprine (Cycloflex, Felexeril)

A

centrally-acting drug for acute local muscle spasm (LMNs)

injury-related spasms

65
Q

diazepam (Valium)

A

centrally-acting drug for acute local muscle spasm (LMNs AND UMNs)

66
Q

metaxalone (Skelaxin)

A

centrally-acting drug for acute local muscle spasm (LMNs)

67
Q

methocarbamol (Carbacol, Robaxin, Skelex)

A

centrally-acting drug for acute local muscle spasm (LMNs)

high risk in the elderly, can slow HR, cause itchy skin rash and sedation

68
Q

vigabatrin (Sabril)

A

centrally-acting drug for acute local muscle spasm (LMNs)

GABA transaminase inhibitor

69
Q

laundry list of centrally-acting drugs for acute local spasms (LMNs)

A

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
Q

another laundry list of drugs used for acute local muscle spasm

A

Chlorphenesin (contraindicated during pregnancy)
Chlorzoxazone
Metaxalone
Methocarbamol
Orphenadrine (anticholinergic properties)
Carisoprodol
Cyclobenzaprine

71
Q

Drugs used for acute local muscle spasm are promoted for…

A

…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
Q

Which drug is the prototype of the group of drugs used for acute local muscle spasm?

A

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
Q

For which conditions is cyclobenzaprine ineffective in treating muscle spasm?

A

cerebral palsy and spinal cord injury

74
Q

cyclobenzaprine’s protein binding and why it’s significant

A

93%, very high, has the ability to interact with other drugs

75
Q

dantrolene’s protein binding and why it’s significant

A

90%, very high, ability to interact with other drugs

76
Q

effects of orphenadril

A

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
Q

baclofen contraindication

A

skeletal muscle spasms caused by rheumatoid arthritis

78
Q

carisoprodol contraindication

A

patients with known hypersensitivity to meprobamate

79
Q

cyclobenzaprine contraindication

A

MI, cardiac conduction disorders, hyperthyroidism

80
Q

dantrolene contraindication

A

active hepatic disease, muscle spasms caused by rheumatoid arthritis

81
Q

tixanidine

A

alpha2 agonist

hypotension, drowsiness, dry mouth

82
Q

botulinum toxin

A

spasticity from cerebral palsy

cosmetics surgery

Pharmacology (1 decks)

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