Skeletal muscle relaxants

Question 1

Baclofen

Answer 1

Centrally acting spasmolytic
GABA-B receptos agonist, selective agonist (Gi): stimulates GABA-B receptors in the central nervous system leading to inhibition of excitatory neurotransmitters—> reduction of muscle tone and spasticity

Orally active
Crosses BBB

Side effects: convulsions, hallucination

Question 2

Tolperisone

Answer 2

Centrally acting spasmolytic
Voltage gated Na+ and Ca2+ channel blocker
Central cholinolytic - it is able to inhibit the action of acetylcholine in the central nervous system

Question 3

Diazepam

Answer 3

It is a benzodiazepine
Centrally acting spasmolytic
GABA-A agonist
Reduces spasticity in the spinal cord
It has anxiolytic effects
Side effects: sedation, tolerance and dependence

BOTH antispasmodic and antispastic

Question 4

Tizanidine

Answer 4

Centrally acting spasmolytic
Alpha2 agonist
BOTH antispasmodic and antispastic

Question 5

Dantrolene

Answer 5

A directly acting spasmolytic - RyR1
Inhibits Ca2+ release from the sacroplasmic reticulum

INDICATION: malignant hyperthermia, multiple sclerosis, spasms, spinal cord injuries

SIDE EFFECTS: muscle weakness, sedation, euphoria, rarely severe hepatotoxic effect

Question 6

Botulinum toxin

Answer 6

Ach release inhibitor
It metabolizes SNARE proteins (SNAP-25, syntaxin, synaptobrevin)
Therapeutic use: hemifacial spasm, after stoke (hand spasm), cervical dystonia, opthalmic purpose, cosmetic procedure

DOSE: 2.5 U (0.1 ml) max 25U

Effevt shows in 2-3 days maximum 5-6 weeks and lasts for 12 weeks

Question 7

Pipecuronium

Answer 7

Non-depolarizing neuromuscular blocker
It has an aminosteroid derivative
It works by competitively blocking the action of acetylcholine at the neuromuscular junction

Duration of action is long >35 minutes

There is no histamine-releaser effect —> histamine release can cause various side effects including hypotension, bonchospasm, and skin infections

Question 8

Cis-atracurium

Answer 8

Non-depolarizing neuromuscular blocker
It has an isoquinoline derivative
Intermediate duration of action (20-35min)

Produces less laudanosine–> so less CNS side effects as laudanosine can cross the BBB

Weak release of histamine

Question 9

Vecuronium

Answer 9

Non-depolarizing competitive neuromuscular blocker

It has an aminosteroid derivative
Intermediate duration of action (20-35min)

It is clinically used as the cardiac effect is more favorable

Question 9

Rocuronium

Answer 9

Non-depolarizing competitive neuromuscular blocker
It has an aminosteroid derivative
Intermediate duration of action (20-35min)

Relatively rapid onset (1-2 minutes)
Used in longer surgical procedures

Question 10

Mivacurium

Answer 10

Non-depolarizing competitive neuromuscular blocker
It has an isoquinolone derivative
Short duration of action (10-20min)

Pseudo-cholinesterase break down quickly
4x more effective than dT
It is a total i.v anesthesia
Antidote: neostigmine
It has a weak release of histamine

Question 11

Succinylcholine

Answer 11

A depolarizing non-competitive neuromuscular blocker
Ultra short acting (5-10 min)
Only i.v
Two linked acetylcholine molecules
Metabolized by plasma cholinesterase

Therapeutic indication: rarely- placement of endotracheal tube at the start of anesthetic procedure and control of muscle contractions in status epilepticus

SIDE EFFECTS: malignant hyperthermia (treatment is dantrolene), arrhythmia, increase intraocular pressure, prolonged respiratory depression, hypersensitive reactions, myalgia (postoperative)

Question 12

Sugammadex

Answer 12

A medication used to reverse the effects of certain non-depolarizing (non competitive) neuromuscular blockers (rocuronium, vecuronium)
It encapsulates the NM blcoker molecules —> inactivating them