Centrally acting skeletal muscle relaxants (Spasmolytics). Datrolene. Botulinum toxin Flashcards
Name the spasmolytics
Baclofen
Diazepam
Tizanidine
Tolperisone
Name the direct acting muscle relaxants
Dantrolene and Botulinum toxin
Name the drugs used in acute muscle spasm with unknown mechanism
Mephensin
Guaiphenesin
Chlorzoxasone
Carisoprodol
What receptor does Baclofen work on?
What sort of drug is Baclofen?
GABA B
GABA B agonist
What are the clinical uses of Baclofen?
- Decrease spasm in patients with MS
- Decrease pain in patients with spasticity by inhibiting substance P in the spinal cord
- Decrease craving in recovering alcoholics
How can Baclofen be administered?
- Oral and intrathecal uses
When would you administer Baclofen intrathecally?
- When patients are not responding to medication by other routes
What are the characteristics of Baclofen when it is administered orally?
Rapid and complete absorption in the oral route
What are the adverse effects of Baclofen?
- Sedation
- Tolerance with chronic use
- Enhancement of sedative and respiratory effect of opiates and alcohol
What sort of drug is Diazepam?
GABA A agonist
What receptor does Diazepam work on?
GABA A receptor
What are the clinical uses of Diazepam?
- Muscle spasm of almost any origin
- Cervical and lumbar syndromes
- Spasticity induced by neurological disorders
What enzyme is Diazepam metabolised by?
CYP1A2
How is Diazepam administered?
Oral and parental routes
What is the dosage of Diazepam in non epileptics?
5-10mg
What is the dose of Diazepam for status epilepticus?
IV 30mg
What sort of drug is Tizanidine?
Alpha 2 agonist
What is the mechanism of action of Tizanidine?
It is an alpha 2 agonist - it reinforces the presynaptic inhibition of the spinal cord.
What are the clinical uses of Tizanidine?
- Muscle spasm of almost any origin
- Cervical and lumbar syndromes
- Spasticity induced by neurological disorders
What enzyme is Tizanidine metabolised by?
CYP1A2
How is Tizanidine administered?
Orally
What are the adverse effects of Tizanidine?
- Asthenia
- Drowsiness
- Dry mouth
- Hypotension
What is the mechanism of action of Mephenesin?
Inhibition of polysynaptic reflexes
What is the mechanism of action of Guaiphenesin?
Inhibition of polysynaptic reflexes
What is the mechanism of action of Chlorzoxazone and Carisoprodol?
Inhibition of polysynaptic reflexes
What is the clinical use of Mephenesin?
Muscle spasm accompanying trauma and inflammation
What is the clinical use of Guaiphenesin?
- Muscle spasm accompanying trauma and inflammation
- Abdominal and anorectal surgery
What are the clinical uses of Chlorzoxazone and Carisoprodol?
Muscle spasm accompanying trauma and inflammation
What are the adverse effects of Carisoprodol?
- It has the potential to be abused
- Meprobamate is hepatotoxic
What type of drug is Dantrolene?
Direct acting Ryanodine receptor antagonist
What is the mechanism of action of Dantrolene?
Dantrolene acts on the skeletal muscular cells to reduce the release of calcium from the SR by interacting with the RyR1 receptor - reducing the actin-myosin interaction.
Cardiac and SMC use RyR2 receptors so they are minimally affected
Why does Dantrolene only affect skeletal muscles?
Because cardiac and SMCs use RyR2 whereas skeletal muscles have RyR1
What is the clinical use of Dantrolene?
Malignant hyperthermia (IV)
Spinal injury
Spasm after stroke (oral)
How is Dantrolene administered in malignant hyperthermia?
IV
How is Dantrolene administered when used to treat spasms after strokes?
Orally
What are the adverse effects of Dantrolene?
Hepatotoxic
Sedation
Generalised muscle weakness
What type of compound is Botulinum toxin?
Exotoxin
Which pathogen produces Botulum toxin?
Clostridium Botulinum
What is the mechanism of action of botulinum toxin?
BT inhibits the release of Ach from vesicles by binding synaptobrevin
What are the clinical uses of botulinum toxin?
Blepharospasm Dystopia Strabismus Cosmetics(wrinkles) Generalised spastic disorders (e.g.,cerebral palsy)
What is blepharospasm?
Uncontrolled movement of the eyelid
What is dystonia?
Uncontrollable muscle contraction