MSK Pharmacology Flashcards by Kathryn Colburn

what are muscle relaxants used to treat?

spasticity and muscle spasms

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features of UMN lesions

site: cerebrum, cerebellum, brainstem, spinal cord
weakness: quad/hemi/para/diplegia
tone: spasticity, rigidity
fasciculation: absent
reflex: hyperreflexive
abdominal reflex: absent depending on spinal level
sensory loss: cortical
EMG: normal nerve conduction

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features of LMN lesions

site: anterior horn cell, nerve root, peripheral nerves, NMJ, muscle
weakness: proximal or distal
tone: hypotonia
fasciculation: present
reflex: hyporeflexive
abdominal reflex: present
sensory loss: peripheral sensation
EMG: abn nerve conduction

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what disordered are associated with spasticity

MS
stroke
CP
spinal cord/brain injury
neurodegenerative dxs

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spasticity definition

muscle stiffness
muscle spasms
rapid muscle contractions/clonus
exaggerated muscle jerks
joint pain

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goal of skeletal muscle relaxants

decrease skeletal muscle excitability
decrease pain
avoid profound decrease in muscle function

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common generic names of skeletal muscle relaxants

baclofen
cyclobenzaprine
diazepam

also:
botuliniuum
carisoprodol
chlorzoxazone
dantrolene
maraxalone
methocabamol
orphenadrine
riluzole
tizanidine

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common brand names of skeletal muscle relaxants

Lioresal
Flexeril
Valium

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antispastic drugs

target spasticity, the velocity dependent increase from hyperirritability of the stretch reflex

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spasmolytics

muscle relaxants
target muscle spasms- involuntary contractions of a muscle/muscle group

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antispasticity drugs vs spasmolytics

antispasticity is for increased muscle tone due a CNS issue while spasmolytics are for painful, acute muscle contractions

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polysynaptic inhibitors

list drugs

type of spasmolytics drug
includes carisoprodol/Soma
+ flexeril/cyclobenzaprine
methocarbamol/Robaxin
orphenadrine citrate/norflex

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polysynaptic inhibitor MOA

acts on polysynaptic reflex in spinal cord
decrease alpha motor neuron excitability to relax skeletal muscle

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polysynaptic inhibitor uses

relieve muscle spasms instead of PT/bed rest
can contain analgesic

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polysynaptic inhibitor side effects

drowsiness
nausea
lightheadedness
vertigo
ataxia
headache
med tolerance

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Diazepam

Valium
benzodiazepine
treat anxiety, seizures, spasticity

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Diazepam MOA

increase inhibition at CNS synapses using GABA
increase effect of GABA by binding gamma receptors and alpha motor neuron inhibition

Diazepam side effects

anxiolysis, anterograde amnesia, sedation, anticonvulsant, antiemesis, muscle relaxation
tolerance
withdrawal - anxiety/tachycardia/death/coma

Diazepam uses

muscle spasms from MSK, spasticity, tetanus toxin spasms

Baclofen

Lioresal
derived from GABA

Baclofen MOA

stimulate GABA receptors in the spinal cord (agonist), inhibit spinal cord transmission to decrease alpha motor neuron firing and relax skeletal muscle

Baclofen uses

spasticity associated with spinal cord lesions
treat para/quadplegia and MS demyelination

Baclofen side effects

transient drowsiness
confusion
hallucination
nausea
mm. weakness
headache

intrathecal injections

directly into subarachnoid space of spinal cord
inject baclofen to decrease severe spasticity

intrathecal baclofen pump

surgical implant programmable pump in abdominal wall to deliver drug at slow cont. rate disruption can cause overdose/withdrawal tolerance can develop

Adrenergic alpha 2 receptor agonist drug name MOA

Zanaflex stimulates alpha 2 receptors on spinal interneurons inhibit interneurons to decrease excitation of alpha motor neurons

uses of alpha 2 agonists

control spasticity (MS, SCI, CVA) as effective as other drugs to decrease spasticity with less generalized mm weakness and other CV side effects

alpha 2 agonist side effects

sedation dizziness dry mouth

gabapentin drug name MOA

Neurontin increase GABA effect in spinal cord (inhibition) originally anti seizure

uses of gabapentin

decrease central spasticity (SCI, MS) used in combination w other drugs like baclofen may reduce chronic pain in those w spasticity

side effects of gabapentin

sedation fatigue dizziness ataxia

dantrolene sodium drug name MOA

Dantrium inhibit Ca release from skeletal muscle SR

dantrolene sodium uses

reduce severe muscle spasticity not for muscle spasms from MSK

dantrolene sodium side effects

generalized muscle weakness hepatotoxicity fatal hepatitis

botulinum toxin drug name MOA

Botox muscle paralytic by local injection for severe spasms inhibits Ach release at skeletal m NMJ

botulinum toxin uses

relax/paralyze muscle remove spastic dominance to allow motor function, improved gait and function, stretch muscles to prevent joint contractures

side effects of botulinum toxin

local irritation limited amount of muscles can be injected limit total dose immune response making future injections less effective

duration of skeletal muscle relaxants

chlorzoxazone - 3-4 carisoprodol - 4-6 metaxalone - 4-6 orphenadrine - 12 cyclobenzaprine - 12-24 diazepam - up to 24 hrs methocarbamol - unknown

alternative to skeletal muscle relaxants for acute low back pain

PT, ibuprofen

alternative to skeletal muscle relaxants for chronic low back pain

skeletal muscle relaxants should not be used PT, NSAIDs, tramadol, opioids

alternative to skeletal muscle relaxants for spasticity

PT, baclofen, tizanidine, dantrolene

effects of spasticity drugs interfering with rehabilitation

motor control problems fxal decline in ADLs decreased alertness weakness tolerance/physical dependence