Skeletal muscle relaxants Flashcards
What muscle relaxers are for acute use
Cyclobenzaprine
What chronic muscle relaxers act on the CNS
Baclofen
Cyclobenzaprine
Diazepam
Tizanidine
What chronic muscle relaxers act on muscles
Dantrolene
Botulinum toxin
Most spasmolytic drugs act
on the CNS to reduce abnormally elevated tone caused by neirologic or muscle end plate disease
What is the MOA of Baclofen
Acts centrally to reduce release of excitatory transmitters in brain and spinal cord
Suppress activity of la sensory afferents, spinal interneurons, and motor neurons
Activates GABA-b receptors pre- and post-synaptically
(admin is PO or intrathecally)
Baclofen is used for
severe spasticity due to cerebral palsy, MS, and stroke
ADE of Baclofen are
Sedation
Muscle weakness
What is the MOA of cyclobenzaprine (flexeril)
Acts centrally to reduce hyperactive muscle reflexes
Poorly understood, but inhibits spinal stretch reflex
Antimuscarinic effects
lasts 4-6 hours, hepatic metabolism
Cyclobenzaprine is used for
acute spasm 2/2 muscle injury or inflammation
ADE of Cyclobenzaprine include
Antimuscarinic
Sedation
Confusion
Ocular effects
Centrally active drugs that are similar to cyclobenzaprine but less studies include
Carisoprodol (soma) Parafon Forte Skelaxin Robaxin Norflex
The drugs similar to cyclobenzaprine do what
Relieve acute muscle spasm caused by local tissue trauma or muscle strain
They act primarily at the level of the brain stem
What is Carisoprodol (soma)
Scheduled IV drug metabolized to meprobamate (another scheduled IV drug)
Sedatives used as muscle relaxants, but evidence of efficacy w/o sedation is lacking
Withdrawal of Carisoprodol and meprobamate after extensive use elicits
physical withdrawal anxiety tremors muscle twitching insomnia auditory and visual hallucinations **So taper slowly over 14 days
What is the MOA of Diazepam (Valium)
Acts centrally to increase interneuron inhibition of primary motor afferents in spinal cord
Facilitates GABA-ergic transmission in CNS to activate GABA-a receptors (post-synaptic)
Central sedation
Lasts 12-24 hours, hepatic metabolism
Uses for Diazepam include
chronic spasm 2/2 cerebral palsy, stroke, or SCI
Acute spasm 2/2 muscle injury
ADE of Diazepam include
Sedation
Antegrade amnesia
Abuse potential
Idiosyncratic reaction: paradoxical hyperexcitable and combative state
What is the MOS of Tizanidine
Acts centrally to inhibit reflex motor output from pre and post-synaptic
A2 agonist in spinal cord (lowers BP)
lasts 3-6 hours, renal and hepatic elimination
Tizanidine is used for
spasms 2/2 MS, CVA, and ALS
ADE of Tizanidine include
weakness
sedation
hypotension
How does Dantrolene work
Acts directly on muscles by blocking calcium release channels in SR
Reduced myosin-actin interaction=weakens muscle contraction
lasts 4-6 hours, IV and oral use
Dantrolene is used for
IV: malignant hyperthermia
oral: Spasms 2/2 cerebral palsy, SCI, and MS
ADE of Dantrolene include
muscle weakness
What is the MOA of Botulinum toxin
Cleaves fusion proteins in nerve endings causing flaccid paralysis
Lasts 2-3 months after direct injection into muscle
Botulinum toxin is used for
Spasms 2.2 cerebral palsy
MS
overactive bladder
migraine headache
ADE of botulinum toxin include
Muscle weakness
Falls
