Central Skeletal Relaxants

Question 1

What are pharmacological ways to decrease spasticity?

Answer 1

decrease hyperactive stretch reflex arc, interfering directly with skeletal muscle, increase action of inhibitory internuncial neurons

Question 2

Acts at all GABA-A synapses mediated in spinal cord: produces sedation in most pts at doses required to significantly muscle tone.

Answer 2

Diazepam

Question 3

potentiate GABAergic inhibition at all levels of neuraxis

Answer 3

BZs

Question 4

muscle relaxing subunit

Answer 4

a2

Question 5

Drugs that interact with GABAa receptors

Answer 5

• benzodiazepines
  -barbiturates
  
  • zolpidem
  • alcohol
  • I.V. anesthetics: etomidate and propofol
  • volatile anesthetics
  • anticonvulsants
  • anthelmintic agent

Question 6

What are some disadvantages of BZs?

Answer 6

risk of psychologic dependence, amnestic effects (anterograde), additive CNS depression, alertness + motor coordination.

Question 7

reverses actions of BZs
does not reverse effects of:
 barbiturates
 meprobamate
 ethanol

Answer 7

Flumazenil( Romazicon)

Question 8

Produces spasmolytic activity at GABA-B receptors, probably by increased K+ conductance.

May also reduce pain in pts with spasticity by less release of substance P in cord.

Answer 8

Baclofen

Question 9

Disadvantages of Baclofen

Answer 9

Needs to be given intrathecal for spasticity and muscle pain not responsive to meds by other routes of admin.

Peripheral ADRs rare due to

Major disadvantage: difficulty of maintaining catheter in subarachnoid space …. but prolonged i.t. admin can  quality of life for pts with severe spastic disorders.

Question 10

For ALS

Answer 10

Riluzole

Question 11

Strong a2 adrenoceptor agonist; related to
clonidine.

Also decreases nociceptive transmission in dorsal horn.

Answer 11

Tizanidine

Question 12

ADRs of tizanidine

Answer 12

droswy, dry mouth, hypotension

Question 13

Direct action on skeletal muscle strength by decreasing excitation-contraction coupling by decreasing release of activator Ca2+ through this
calcium channel by binding to ryanodine receptor.
Cardiac muscle and smooth muscle minimally depressed

Answer 13

Dantrolene

Question 14

good treatment of malignant hyperthemia and neuroleptic malignant syndrome

Answer 14

dantrolene

Question 15

Tx for ophthalmic purposes and local muscle spasm. Prevents ACh vesicle release

Answer 15

Botulinum

Question 16

Two agents that are anticholinergic acting

Answer 16

Cyclobenzaprine (FLEXERIL)*
- structural relationship to tricyclic antidepressnts
- not effective in treatment of muscle spasms caused
by CNS pathology
- strong antimuscarinic actions:
significant sedation

Orphenadrine (Norflex)