Skeletal muscle relaxants/ antispastic drugs Flashcards
What type of drug is baclofen?
What pathway is that receptor on?
GABA receptor agonist
Baclofen binds to GABA receptors in the descending excitatory pathway, which reduces the release of glutamate.
What is the MoA of baclofen?
binds to GABA receptor in descending excitatory pathway, reducing release of glutamate and thus decreased skeletal muscle contraction
This is particularly useful for treating spasticity.
What conditions is baclofen used to treat?
- Spasticity in MS, ALS, stroke, head injury
- Spinal cord injury
- Cerebral palsy
What are common side effects of baclofen?
CNS depression: drowsiness, dizziness, weakness, fatigue
GI symptoms: nausea, constipation, urinary retention
Abruptly stopping intrathecal dosing dangerous for rebound effects
What is the receptor type and action of pancuronium?
Nicotinic M (Nm) receptor antagonist
It competitively blocks ACh receptors at the neuromuscular junction.
What type of muscle relaxant is pancuronium?
Non-depolarizing muscle relaxant
or Non-depolarizing neuromuscular blocker
What is the primary use of pancuronium?
Induce skeletal muscle relaxation during surgery and intubation
or ECT therapy
What is the MoA of pancuronium?
“nondepolarizing because it is blocking action
Competitively blocks ACh receptors at the neuromuscular junction, leading to paralysis”
What is the receptor type and action of succinylcholine?
Nm receptor agonist.
What type of muscle relaxant is succinylcholine?
Depolarizing muscle relaxant
Succinctly, it acts as an Nm receptor agonist.
What is the mechanism of action of succinylcholine?
It binds to the Nm receptor for a prolonged period, causing conformational change and inactivation, preventing twitch summation and sustained contraction
This leads to muscle relaxation.
What are the primary uses of succinylcholine?
- Rapid sequence intubation
- Short surgical procedures
It is especially useful in situations requiring quick muscle relaxation.
What are the risks associated with succinylcholine?
- Hyperkalemia
- Malignant hyperthermia
- Muscle fasciculations
- post-op muscle pain
It is contraindicated in burn injuries, neuromuscular disorders, or denervation injuries.
What are the phases of block for succinylcholine?
- Initial block: depolarization
- Sustained desensitization block
Describe initial block for succinylcholine.
equivalent to excess Ach:
binds -> activates -> very strong response
Describe sustained desensitization block for succinylcholine.
equivalent to R inactivation:
prolonged occupancy of R by succ
->
change in config. of R
->
prevents membrane depolarization and a sustained muscle contraction
What is twitch summation?
new twitch before prev relaxed;
membrane potential of that musc cell remains ABOVE threshold
What type of drug is botulinum toxin?
ACh release inhibitor at the neuromuscular junction
It inhibits the fusion of vesicles to the neuron’s membrane.
What is the mechanism of action of botulinum toxins?
- Inhibits membrane fusion proteins necessary for exocytosis of Ach by motor neurons;
- blocks excitation secretion coupling
- causes skeletal muscle paralysis
This prevents muscle contraction at the neuromuscular junction.
What are the primary uses of botulinum toxins?
- Strabismus
- Facial wrinkles
- Migraines
- overactive bladder
What are the potential side effects of botulinum toxin injections?
- Injection site pain
- Localized muscle weakness
- Potential for systemic spread if improperly dosed (symmetric descending paralysis)
txt systemic spread w/antitoxin or botulinum immune globulin
What type of drug is dantrolene?
ryanodine receptor antagonist;
Inhibitor of Ca²⁺ release; muscle relaxant
It specifically inhibits Ca2+ release to prevent muscle contraction.
What are the primary uses of dantrolene?
- Malignant hyperthermia
- Neuroleptic malignant syndrome
- Spasticity
It is used in critical care situations to manage severe muscle contraction.
What is the MoA of dantrolene?
Dantrolene depresses excitation-contraction coupling in skeletal muscle by binding to the ryanodine receptor 1, and decreasing intracellular calcium concentration.
Ryanodine receptors mediate the release of calcium from the sarcoplasmic reticulum, an essential step in muscle contraction.
How does dantrolene help malignant hyperthermia?
stops muscle rigidity, stops hypermetabolic state (decr O2 comsumption and CO2 prod), decreases body temp, prevents rhabdo and multiorgan failure
