Pharmacology Muscle Relaxants Flashcards
What is the primary goal of muscle relaxers
Selectively decrease muscle excitability
What is meant by selectively decreasing excitability
Only decrease excitability of the muscles with too much excitability
Muscle spasm
Result of an injury to a muscle or a peripheral nerve, causes a tonic contraction.
What is a tonic contraction
A sustained Strong solid contraction over time
Muscle spasticity
Damage to the CNS resulting in exaggerated Stretch reflexes
What agents are used to treat muscle spasms
Polysynaptic inhibitors
Diazepam (Valium)
What are Polysynaptic inhibitors
They act on the Polysynaptic reflex arc to decrease excitability of alpha motor neuron
Common Polysynaptic inhibitor names
Carisoprodol Chlorophenesin Chlorzoxazone Cyclobenzaprine Metaxalone Methocarbamol Orphenadrine citrate
How do anti-spasm drugs work
Work through sedative effect
What shoulder be coupled with anti-spasm drugs during rehab
Aggressive PT
When and how should anti-spasm drugs be taken away
ASAP (3-4 days), and then use PT to continue anti-spasm effects
What type of agent is diazepam and what was it originally made for
Benzodiazepine, made as an anti-anxiey first
How does Diazepam(valium) work
Increases the inhibitory effects of GABA.
How does Valium increase the effects of GABA
GABA binds to the BDR protein allowing Cl- to enter the muscle making the muscle more negative and harder to excite. The Valium increases the binding of GABA so it can stay on the BDR protein longer and allow more Cl- to enter.
What is a draw back of Valium
Excess amounts will cause sedation
What agents are used to treat spasticity
Diazepam (Valium) Baclofen Alpha-2-agonists Gabapentin Dantrolene Botulinum toxin
How does diazepam treat spasticity
Acts on the CNS to increase GABA mediated inhibition, also causes sedation
What is the best patient to treat with diazepam
Pt who has spasticity and anxiety issues
How does Baclofen work
Is a synthetic form of GABA which activates the receptors (GABAb) to open channels for Cl-
How is Baclofen administered
Orally or Intrathecally (spinal injection)
Why use intrathecal over oral
Takes less dosage to get same results
Better effect
Injected locally
What is a intrathecal Baclofen pump
Catheter placed in the abdomen that pumps the baclophen into the subarachnoid space at the level of the cauda equina
Drawbacks of the intrathecal Baclofen pump
Repitory problems
Stupor
Coma
Withdrawal if the pump malfunctions and does not pump anymore
What are alpha-2 agonists
Stimulate a receptor on interneurons in the spinal arc. These alpha-2 receptors inhibit the excitability of the interneurons
What is the primary agent that is a alpha-2 receptor
Tizanidine
How does Gabapentin work
Enhances GABA by blocking Calcium from entering and decreasing glutamate. More effective GABA means decreased excitability
How does dantrolene sodium (dantrium) work
Blocks the entry of Ca into skeletal muscle, so there is less actin/myosin interactions causing weaker or less muscle contractions
What makes dantrolene sodium different from other muscle relaxants
Is the only one that acts directly on the skeletal muscle where as the others act on the CNS
What is botulinum toxin
Local injections used for severe spasms such as torticollis and laryngospasms. Causes paralysis of muslce
Botulinum toxin mechanism of action
Eats up the connection proteins so the vessicles don’t release AcH. Now when there is an action potential it will have no effect on the muscle.
How long does it take for botulinum to take effect and how long does it last
3-7 days
Lasts 2 to 3 months
What are some of the problems or limitations with botulinum
Immune system may create antibodies that destroy the toxin
Can only use on one muscle.
Must pick the muscle that you believe would increase function the most.
Signs of OD from Botulinum toxin
Drooping of eyes
Difficulty speaking
Muscle weakness
Respiratory problems
What are some concerns for muscle relaxants
Weakness
Sedation
Drastic change in tone in short time
