Hyperexcitable muscle disorders, antispasm and antispastic medications - Study guide Flashcards
Order of process of muscle contraction
- entry of Na+ = intiate action potential thru sarcolemma and T-tubules
- activate voltage-sensitive receptors = trigger Ca2+ release into cytosol
- Ca ions bind to troponin -> changes shape -> removes block of tropomyosin -> active sites exposed
- contraction by myosin heads attaching and detaching with release of energy
- Removal of Ca2+ by active transport into the SR
- blocking respored and fibers relax
What is the difference between upper motor neuron and lower motor neuron lesion?
What is spasticity?
Velocity dependent increase in muscle tone
- because of increased excitability of the muscle stretch reflex
What is a muscle spasm?
Involuntary muscle contraction
What are the common neurologic disorders associated with spasticity?
MS
Stroke
Cerebral palsy
spinal cord and brain injuries
Neurodegenerative diseases affecting the:
- uppermotor neuron
- pyramidal
- extrapyramidal pathways
What are the sx of severe spasticity?
- muscle stiffness
- muscle spasm
- rapid muscle contraction (clonus)
- fixed joints (contractions)
- exaggerated muscle jerks
- pain or tightness around the joint
What are the primary goals of skeletal muscle relaxants?
- selective decrease in skeletal muscle excitability
- decrease pain w/o causing a profound decrease in muscle function
What are the agents used for skeletal muscle relaxants?
anti-spasticity or antispasmodic
What is brand name of baclofen?
Lioresal
What is the brand name of chlorzoxazone?
Parafon forte
What is the brand name of cyclobenzaprine?
Flexeril
What is the brand name for Dantrolene?
dantrium
What is the brand name of diazepam?
valium
What is the brand name of tizanidine?
zanaflex
What is the brand name of metaxalone?
Skelaxin
What is the mechanism of action for baclofen?
Acts on the GABA which facilitates spinal inhibition of motor neuron = inhibits reflexes and decrease spasticity
What are the uses for baclofen?
- treat spasticity with SC lesions
- for MS
- doesn’t cause as much generalized muscle weakness
What are the adverse effects of baclofen?
- transient drowsiness (goes away in a few days)
- confusion and hallucinations with CVA or elderly
- nausea
- mm weakness
- headaches
What is the route of administration of baclofen?
Oral
Intrathecal
What is the mechanism of action for cyclobenzaprine?
poorly understood inhibition of muscle stretch reflex in the spinal cord
What are the adverse of effects of cyclobenzaprine?
blurred vision
dizziness
drowsiness
lightheadness
dryness of the mouth
What is the uses for cyclobenzaprine?
relief of muscle spasms
What is the route of administation for cyclobenzaprine?
oral route is the usual way but can also be intravenous
What is the mechanism of action for tizanidine?
- stimulates alpha-2 receptors in the spinal interneurons
- cause interneuron inhibition = decrease excitatory input into the alpha motor neuron
- decreases excitatability by both pre and post synaptic inhibition
What are the uses for tizanidine?
- control spasticity from spinal lesions and central lesions
- as effective as others
- milder side effects and less generalized mm weakness
- doesn’t cause as much hypotension and other CV side effects compared to clonidine
What are the adverse effects of tizanidine?
sedation
dizziness
dry mouth
Less generalized weakness than baclofen or diazepam
What is the route of administration for tizanidine?
oral or can also be intraveous
What is the mechanism of action for diazepam?
facilitate GABAergic transmission in the CNS
increases GABA-mediated inhibition of alpha motor neuron -> less excitability -> muscle relaxation
What are the uses of diazepam?
Extensively in treating spasms associated with musculoskeletal injuries
What are the adverse effects of diazepam?
- sedation and general reduction in psychomotor ability
- long term use also limited by tolerance and dependence
- sudden use withdrawl = seizues, anxiety, agitation, tachycardia and even death
- overdose of diazepam = coma or death
What is the mechanism of dantrolene?
stops the release of Ca from skeletal muscle into the SR
What are the uses of dantrolene?
Treating severe spasticity
not presribed to treat mm spasms caused by musculoskeletal injury
Used in traumatic cord lesions, advanced MS, cerebral palsay, CVA
What are the adverse effects of dantrolene?
- generalized muscle weakness is the most common
- severe hepatoxicity
- fatal hepatitis
How is dantrolene use be counterproductive?
increased motor function with a decreased spasticity is offset by generalized mm weakness
What are the uses for metaxalone?
mod to strong muscle relaxant used in symptomatic treatment of musculoskeletal pain
What is the mechanism of action of metaxalone?
Has not yet been established but is possibly due to general CNS depression
What are the adverse effects of metaxalone?
drowsiness
irritability
upset stomach
There’s a crap load but these are the most common (???)
What is the route of administration for metaxalone?
oral route
taken 3-4x per day
What is the use of chlorzoxazone?
relax certain muscles in the body to get relief caused by acute musculoskeletal disfunctions
What is the mechanism of action for chlorzoxazone?
MOA is unknown but might act @ the spinal cord and subcortical levels of the brain
- this slows multisynaptic reflex arcs that has to do with muscle spasms
What are some adverse effects of chlorzoxazone?
Drowsiness, dizziness, lightheadedness, tiredness, upset stomach, or headache may occur
What is the route of administration for chlorzaxazone?
Oral route
What is a patient controlled analgesia?
safe way for people to give themselves intravenous and pain medicine when they need
What are the benefits of PCA?
- allows for better pain control with less side effects
- but does need patient awareness and cognitive ability
- increases patient satisfaction
What is nociceptive pain?
pain coming from actual or threatened damage to non-neural tissue
= activation of nociceptors
What is neuropathic pain?
pain from neurons or somatosensory nervous system
What is the difference between nociceptive vs neuropathic pain?
Picture
What are the causes of acute pain?
generally known what caused the pain
What are the causes of chronic pain?
often unknown
What is the duration of pain for acute pain?
short
well-characterized
What is the duration of pain for chronic?
Persistent after healing
greater than 3 months
What is the treatment approach of acute pain?
When the cause is fixed = pain goes away
- usually self limiting
What is the treatment approach of chronic pain?
the underlying cause and pain disorder
- pain control is the goal and not cure
