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Musculoskeletal System > Pharm Muscle Relaxants > Flashcards

Pharm Muscle Relaxants Flashcards

1
Q

Skeletal muscle relaxants

A

Manage spasticity (upper motor neuron) and spasms (lower acute neuron) in pts w/ LMN and UMN lesions

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2
Q

Spasticity

A

Stiff or rigid muscles (tightness)
Abnormally elevated muscle tone
Increase in muscle tone or contractions cause movements to be stiff and awkward
Considered a permanent condition and may progress to disabling condition if therapy is not instituted

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3
Q

Two classes of muscle relaxants

A

Neuromuscular blocking drugs
-depolarizing (succinylcholine)
-nondepolarizing - long duration (tubocurarine), short duration (mivacurium)
Skeletal muscle spasmolytic drugs
-For chronic conditions: CNS action (Baclofen, diazepam, tizanidine); muscle action (dantrolene)
-For acute conditions: cyclobenzaprine

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4
Q

Nondepolarizing neuromuscular blocking drugs

A

Can be used in conjunction with procedures requiring anesthetics e.g. Tracheotomy

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5
Q

Succinylcholine

A

nACh agonist/Tx short term muscle relaxant in endotrach intubation/Mentioned: contraindicated with pseudocholinesterases (butyrylcholinesterase) as it breaks succinylcholine very quickly

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6
Q

MOA of succinylcholine

A

Depolarizing skeletal muscle relaxant
It combines with cholinergic receptors of the motor end plate to produce depolarization (observed as fascinations or spasms)
***** “persistent” depolarization of the neuromuscular junction leading to desensitization and eventually muscle relax

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7
Q

Therapeutic use of nonpolarizing neuromuscular blocking drugs

A

High dose will be administered to paralyze person prior to giving potassium bromide to kill them
Used as an adjunctive therapy for general anesthetics ; used to produce muscle paralysis in order to facilitate surgery or artificial ventilation

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8
Q

CNS action spasmolytic drugs

A

Treat muscle spasms or muscle cramps

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9
Q

Muscle action of spasmolytic drugs

A

Treat Spasticity

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10
Q

Therapeutics of spasmolytics

A

Drug that reduces abnormally elevated muscle tone (spasticity) without paralysis

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11
Q

What are Spasms or cramps

A

Spasms are sudden, violent, painful, involuntary contractions of a muscle or group of muscles
Tend to occur in acute setting and are temporary (whereas spasticity appears in a chronic setting and are persistent)

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12
Q

What neurons are involved in spasms?

A

Motor neurons
Balance between musculoskeletal movement and body posture
Cell bodies resides in the ventral ganglia
LMN
Acetylcholine is chief neurotransmitter

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13
Q

Action potentials and NMJ

A

Action potentials by motor neurons are conducted directly to nerve terminals in muscle fibers that form synapses called neuromuscular junctions

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14
Q

Acetylcholine is released from the nerve terminal to what receptors on the muscle for contraction ?

A

Nicotinic receptors

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15
Q

What type of injury involves Spasticity ?

A

Upper motor neuron
Spasticity is an increase in the passive stretch resistance (which is the force of gravity on the limb or on the body weighing down on it) of a muscle or muscle group

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16
Q

What are the etiologies of spasticity (more permanent)?

A

Head injuries, cerebral palsy, Ms, stroke
Cerebrovascular accident
Closed head injury
Hemiplegia- paralysis of the arm, leg, trunk on the same side of the body
Paraplegia- spinal injury results in an impairment in motor or sensory function of the lower half of person’s body
Quadriplegia- paralysis or partial paralysis of all limbs of the body
MS -demyelination of neurons
Poliomyelitis
Spinal cord trauma

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17
Q

Compare spasm and spasticity

A

Spasm - sudden, violent, painful involuntary contractions of a muscle or group of muscles
Mediator is lower motor neurons
Spasticity- increased muscle tone, or muscle contractions that cause stiff, awkward movement
Mediator is upper motor neurons

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18
Q

What are etiologies for spasm?

Acute/treatable

A 
Bursitis
Dislocation
Fracture
Epilepsy
Herniated disc
Hypocalcemia
Myositis, neuritis 
Strains
Whiplash injuries
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19
Q

Atracurium
Pancuronium
Gallamine

A

Neuromuscular blockers
Muscle relaxants
Indirect acting bc they interfere with transmission at the neuromuscular end plate and are not centrally acting drugs

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20
Q

Baclofen, diazepam, tizanidine

A

Spasmolytics that have traditionally been called “centrally acting” muscle relaxants
However, dantrolene is a peripherally acting and has no significant central effects

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21
Q

Major uses of spasmolytic drugs

A

Skeletal muscle relaxants
For muscle strains and back pain
Muscle strains-accompanied by pain
Back pains-poor posture, abnormal gait

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22
Q

Stretch reflex arc

A

UMN (Ia afferents carried from spindle fiber) acts at all times on interneurons to cause inhibition if muscle contraction ?
A lesion at UMN prevents this inhibition and results in spasticity

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23
Q

What lesion leads to spasticity?

A

UMN

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24
Q

Interneurons

A

2 small interneurons that act as inhibitory by release of GABA and glycine

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25
Q

Where are the cell bodies for LMN?

A

Ventral root ganglion

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26
Q

Centrally acting skeletal muscle relaxants

A

Drugs used to treat spasticity or UMN lesions
Baclofen
Botox
Diazepam -acts on alpha-2 (centrally active)
Tizanidine

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27
Q

Peripherally acting drug for spasticity

A

Dantrolene which acts on the muscle itself

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28
Q

Baclofen

A

GABA mimetic - drug may act by mimicking the actions of GABA on spinal neurons
Acts within the spinal cord to suppress hyperactive reflexes
Involved in regulation of muscle movement
Structurally analog of GABA selective to GABAb
Longer half life than GABA

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29
Q

Baclofen and diazepam

A

Assists in GABA-mediated signal transduction

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30
Q

Diazepam

A

Facilitates GABA-mediated presynaptic inhibition
Anti-anxiety agent
Member of Benzodiazepine
Tx. Spasticity and spasms (LMNs and UMNs)
Can be used in pts with muscle spasm of almost any origin, including local muscle trauma

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31
Q

Tizanidine

A

Acts on UMNs and inhibits their firing
Stimulates relaxation
Acts on alpha2 adrenergic agonist (central)
Can be used for neuropathic pain but it interferes with alpha 2
Tx hypotension, drowsiness, dry mouth ? Or causes these?

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32
Q

MOA of Baclofen

A

The drug interferes with the release of excitatory transmitters
Stabilizes the neuron and prevents it from firing ; allows rigid

33
Q

Dorsal horn of the spinal cord

A

Sensory going in

34
Q

Ventral horn of the spinal cord

A

Motor going out

35
Q

Baclofen action

A

Acts on the level of spinal cord to restore inhibiting tone

36
Q

Therapeutic use of Baclofen

A

Can reduce spasticity associated with MS, spinal cord, injury, and cerebral palsy
Not effective in stroke!!!!
Decreases flexor and extensor spasms
Suppresses resistance to passive movement
Reduce the discomfort of spasticity and allowing increased performance

37
Q

Passive resistance of muscle

A

Muscle tone is continuous and its passive contraction

In other words, it is the muscle’s resistance to passive stretch during resting state

38
Q

Baclofen is preferred over what drug in patients whose spasticity is associated with significant muscle weakness?

A

Dantrolene

39
Q

Baclofen is effective (does not relieve spasticity) of what disease ?

A

Parkinson’s

40
Q

Baclofen’s pharmacokinetics

A 
Good absorption 
Time to peak concentration is 2-3 hrs
Variable onset of action (hours to days) 
Half life - 2.5-4 hours 
Metabolized in the liver 
Excreted in the kidneys
41
Q

Baclofen accumulation

A

Since GABA recpts are everywhere …
If it accumulates in the body, it can act on other GABA receptors, causing sedation, drowsiness, and dizziness bc it depresses the CNS (therefore pts shouldn’t drink alcohol while taking it

42
Q

Adverse effects of Baclofen

A

The most common side effects involve the CNS and GI tract
CNS effects: depressant, drowsiness, dizziness, weakness, and fatigue
-most intense during the early phase of therapy and diminish with continued drug use (tolerance?)

43
Q

Contraindications of Baclofen

A

Pts should be cautioned against the use of alcohol and other CNS depressants Since Baclofen potentiates the depressant action of the drugs

Skeletal muscle spasms caused by rheumatoid arthritis

44
Q

Dantrolene

A

Ryanadine receptor antagonist - prevents calcium release
Ryandine rcpt mediates ca2+ associated ca2+ release
Acts directly on skeletal muscle to relieve spasticity from UMN injury
(Unlike Baclofen and diazepam)
Relieves Sx of malignant hyperthermia by acting on the SR to block calcium release

45
Q

What receptor does diazepam bind to?

A

Act within. The CNS by facilitating GABA mediated presynaptic inhibition (mimics the actions of GABAa at rcpts in the spinal cord and brain)
Binds to specific subunit of GABA rcpt

46
Q

Tx, SfX, and dosage of diazepam

A

SfX: Produces sedation in last pts at doses required to significantly reduce muscle tone
Causes dizziness
Minimize sedation by administering low doses
Dosage begins at 4 mg/d gradually increased to 60 mg/d
Drug preferred over dantrolene in pts with marginal strength -wont cause more muscle weakness unlike other drugs

47
Q

High affinity of drug to plasma proteins

A

Drug interactions

Long half life

48
Q

Baclofen drug interactions

A

Alcohol
Antihistamine-
CNS Depressants -potentiates each other by causing excessive CNS depression
MAO inhibitors

49
Q

What effects are associated with the drug interactions for Baclofen ?

A

increase risk of hepatotoxicity with combination of chlorzoxazone and alcohol
Increase CNS depression

50
Q

Chlorzoxazone

A

Tx spasms

51
Q

MOA of dantrolene

A

Suppression of calcium release from sarcoplasmic reticulum (SR)
Will lead to decrease ability of skeletal muscle to contract
Also used to tx Malignant hyperthermia

52
Q

Malignant hyperthermia

A

Autosomal dominant
Defect in the Ryanodine recpt causing more ca2+ release
Severe muscle contractions
Fast rise in body temperature
A life-threatening syndrome that can be triggered by any general anesthetic and by succinylcholine, a neuromuscular blocking agent

53
Q

Tx, SfX, and therapeutic use dantrolene

A

Minimal effects on smooth muscle and cardiac muscle which is a therapeutic advantage - therefore, it wouldn’t increase TPR and Bp
Tx. Spasticity associated with MS, cerebral palsy, and spinal cord injury, malignant t hyperthermia ( inherited, muscle breakdown)
Can be associated with significant decrease in strength ( generalized reduction in the ability for skeletal m. To contract)

54
Q

Sx of malignant hyperthermia

A

Muscle rigidity
Profound elevation of temperature
Heat is generated by muscle contraction occurring secondary to massive release of calcium from the SR

55
Q

Adverse toxic effects of dantrolene

A

Hepatic - dose related liver damage - most serious
Liver damage incidence 1/1000
Death - due to extensive liver damage
CNS : drowsiness, dizziness, malaise, lightheadness, insomnia, fatigue, confusion
Urinary : increased urinary frequency

56
Q

What tests should be performed prior to tx with dantrolene

A

Liver function test

Monitor liver damage

57
Q

Dantrolene drug interactions

A

Increased toxicity : estrogen, CNS depressants, Clindamycin, Verapamil, Warfarin, Clofibrate, Tolbutamine

58
Q

Dantrolene-estrogen

A

Hepatotoxicity
Post-menopausal women on estrogen regimen
Produces additive effect to liver toxicity

59
Q

Dantrolene-CNS depressant

A

Sedation

60
Q

Dantrolene-Clindamycin

A

Increased neuromuscular blockage

61
Q

Dantrolene-verapamil

A

Hyperkalemia and cardiac depression

Verapamil is a calcium channel blocker - treat angina and hypertension

62
Q

Warfarin, Clofibrate, Tolbutamine

A

Drug interaction with dantrolene

Interaction occurs at the level of enzyme mechanism

63
Q

Drugs for muscle (acute local) spasms or LMN legions

A

Carisoprodol, Chlorophenesin, Chlorzoxazone, cyclobenzaprine, diazepam, metaxalone, methocarbamol, vigabratin

64
Q

Carisoprodol

A

Metabolized to a different drug used to treat anxiety - has sedative or hypnotic properties

Contraindicated with pts that have known hypersensitivity to meprobamate

65
Q

Meprobamate

A

Highly addictive
Metabolite of carisprodol
Combined with rohypnol (date rape drug)

66
Q

Chlorophenesin

A

Anti fungal and antibiotic
Potential interaction with Baclofen
Contraindicated during pregnancy !

67
Q

Chlorzoxazone

A

For spasms from trauma or electrolyte imbalance

68
Q

Cyclobenzaprine

A

Injury- related spasms
May be regarded as the prototype of the group (acute local spasm drugs)
Has muscuranic effects - contraction of the detrusor muscle by bladder - urinary incontinence?)
Will not work well in pts with muscle spams due to cerebral palsy or spinal cord injury

69
Q

Metaxalone

A

For strains, sprains
Increase absorption with food
Can cause headaches, dizziness, but less addictive than carisprodol

70
Q

Methocarbamol

A

High risk in elderly
Skeletal muscle relaxant
Slow down heart
May cause skin rash, itching, and significant depression of the CNS (therefore can cause sedation)

71
Q

Vigabratin

A

GABA transaminase inhibitor

72
Q

GABA transaminase

A

uses GABA as a substrate to produce something else (transforms it; uses it up)
Inhibition of this enzyme allows GABA to linger, allowing significant relief from spasms and pain

73
Q

Orphenadrine

A 
Anti cholinergic properties 
Tx acute local muscle spasm ; fibromyalgia (acting on NET)
Antihistamine of H1 receptor
inhibits muscuranic rcpts 
Inhibits NMDA rcpt in CNS 
Inhibits NE reuptake by blocking NET
74
Q

How do the drugs for acute local muscle spasm work?

A

Promoted for the relief of acute temporary muscle spasm caused by local trauma or strain
Most act as sedative or at the level of spinal cord or brain stem

75
Q

What promotes long half life and drug interaction?

A

High level of protein binding
Cyclobenzaprine has 93% protein binding
Dantrolene has high protein binding but half life is in hours
And half life is 1-3 days but unlike other muscle relaxants that have half life in hours

76
Q

Contraindications of cyclobenzaprine

A

MI, cardiac conduction disorders, hyperthyroidism

77
Q

Contraindications of dantrolene

A

Active hepatic disease

Muscle spasms caused by rheumatoid arthritis

78
Q

Botox

A

Binds to synaptobrevin, syntaxin, or SNAP-25
Depending on the type

Tx spasticity from cerebral palsy, cosmetic surgery

Musculoskeletal System (27 decks)

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