Pharmacology - Skeletal Muscle Relaxants Flashcards
Give an example of a depolarizing neuromuscular depolarizing drugs?
- Succinylcholine
Give an example of a long duration and a short duration non-depolarizing neuromuscular blocking drugs?
- Long duration: tubocurarine
- Short duration: mivacurium
Give 3 types of drugs that work on the CNS of chronic spasmolytic conditions?
- baclogen, diazepam, tizanidine
Give 3 type of drug that work on the muscle for chronic conditions of chonic spasmolytic conditions?
- dantrolene
Give one drug that treats acute conditions of spasmolytic conditions?
- Cyclobenzaprine
What are neuromuscular blocking drugs?
- They are used to produce muscle paralysis in order to facilitate surgery or artificial ventilation.
What are spasmolytic drugs?
- A drug that reduces abnormally elevated muscle tone (Spasticity) without paralysis.
What are Spasms?
Spasms are sudden, violent, painful, involuntary contractions of a muscle or group of muscles.
What type of neurons are involved in spasms?
- There is involvement of Motor neurons, which maintain a balance between musculoskeletal movement and body posture.
How does a contraction occur in a spasm?
- Acetylcholine is released from the nerve terminal and stimulates nicotinic receptors on the muscle producing a contraction.
What is the difference between a spams and spasticity?
- Spasticity is an increase in the passive stretch resistance of a muscle or muscle group that cause stiff awkward movements.
- Spasm: a sudden, violent, painful involuntary contractions of a muscle or group of muscles
Is spasticity considered acute or permeant? What can assist in its management?
- Permeant
- Therapy
What are the common causes of spasticity?
- Head injuries
- Cerebral palsy
- MS
- Stroke
- Others: Hemiplegia, Paraplegia, Quadriplegia, Poliomylelitis, Spinal Cord trauma, Cerebrovascular accident
Are spasm or spasticity mediators Lower motor neurons (LMN)
-Are Spasm or Spasticity mediators Upper motor neurons (UMNs)
- LMN : Spasm
- UMN : Spasticity
What are some etiologies for Spasm?
- Bursitis
- Fracture
- Herniated disc
- Hypocalcemia
- Other: Dislocation, Epilepsy, Myositis, Neuritis, Strains, Whiplash injuries
What are skeletal muscle relaxants members of?
- Where do they interfere with transmission?
- What are they definitely not?
- What are some examples of them?
- Members of neuromuscular blockers
- Interfers with transmission at the neuromuscular end plate.
- The are definitely not central acting drugs!!
- Atracurium, pancuronium, and gallamine
Where do a majority of spasmolytics act?
What are some examples of spasmolytics?
Dantrolene (a spasmolytic) acts where?
- Centrally acting
- Baclogen, diaszepam, tizanidine
- Peripherally acting ( the only apparent exception)
What are the two main treatments for spasmolytic drugs?
- Muscle strains and back pain
What is the stretch reflex arc pathway?
Upon muscle stretch of a muscle, Ia afferents send a signal to the dorsal root, this signal is carried by an interneuron that then sends an inhibitory signal ( via Gaba) out through the ventral root via extrafusal efferents that effect muscle relaxation.
When is the stretch reflex arc active?
It is tonically active at all times
Name 4 centrally-acting skeletal muscle relaxants that treat spasticity?
- Baclofen
- Botulinum toxin type A
- Diazepam
- Tizanidine
What is the one peripherally-acting drug for spasticity?
- Dantrolene
Where does Baclofen work and what does it do?
What is it an analog of?
Acts within the spinal cord to sprpress hyperactive reflexes involved in regulation of muscle movement.
- It is a structural analog of GABA (which may act by mimicking GABAs actions)
What type of GABA is Baclofen more selective for?
- GABA B > GABA A allowing it to stick around for longer
What is the postulated sites of spasmolytic action of diazepm and baclofen in the spinal cord?
Diazepam facilitates GABA-mediated presynaptic inhibition and Baclogen interferes with release of excitatory transmitters
What receptors do Benzodiazepine act on and what NT does it reinforce?
- Acts on the ryanodine receptor and reinforces GABA
What is the big picture point of Baclofen action to remember?
- Acts at the level of spinal cord to restore inhibiting tone
What can therapeutic use of baclofen reduce and what disorders can it be used for?
- Reduce spasticity and associated with MS, spinal cord injury, and cerebral palsy. (Not effective in a stroke)
What does Baclofen actually do?
- Decreases flexor and extensor spasms and suppresses resistance to passive movement, hopefully reducing the discomfort of spasticity and allowing increased performance.
During what conditions is Baclofen preferred to dantrolene?
- Does Baclogen relieve the spasticity of Parkinson’s?
- in patients whose spasticity is associated with significant muscle weakness.
- DOES NOT relieve Parkinson’s disease
Baclofen: what is the time to peak conc? what is the half-life? Where is it metabolized? What is it excreted by?
- Peak conc.: 2-3 hours
- Half-life: 2.5-4 hours
- Metabolized in liver
- Excreted in the kidneys
Where do Baclofen’s most common side-effects occur?
What are the CNS effects?
- in the CNS and GI tract (sites of action and the site of metabolization/excretion)
- CNS depressant, Frequently causes drowsiness, dizziness, weakness, and fatigue.
What are the contraindication for Baclofen?
What can occur if ignored? What could potentiate the problem?
- Alcohol intake, antihistamines, MAO inhibitors, and CNS depressants (since baclogen potentiates the depressant action of these drugs)
- CNS depression Increased risk of hepatotoxicity with combination of chlorzoxazone and alcohol
What family is diazepam a member of?
What is its MOA?
- A member of the benzodiazepine family ( the only benzodiazepine labeled for treating spasticity)
- It acts within the CNS by facilitating GABA- mediated presynaptic inhibition in the spinal cord and brain
