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Skeletal Muscle Relaxants (Pharmacology) - Coggle Diagram
Skeletal Muscle Relaxants (Pharmacology)
1.Depolarizing
Receptor Interactions
Stimulates ANS ganglia and M receptors
Pharmacokinetics
Parenteral: short action, inactivated by plasma esterases
Mechanism of Action
Agonist at ACh-N receptor causing initial
twitch then persistent depolarization
Adverse Effects
Muscle pain, hyperkalemia increased intragastric and intraocular pressure
Drugs
Succinylcholine
2.Nondepolarizing
Receptor Interactions
ANS ganglion block (tubocurarine) ,Cardiac M block
(pancuronium)
Pharmacokinetics
Parenteral use, variable disposition
Spontaneous inactivation (atracurium, cisatracurium) Plasma ChE (mivacurium)
-Hepatic metabolism rocuronium, vecuronium)
-Renal elimination (doxacurium),pancuronium, tubocurarine)
Mechanism of Action
Competitive antagonists at skeletal muscle ACh-N receptors
Adverse Effects
Histamine release
(mivacurium, tubocurarine)
Laudanosine formation
(atracurium) Muscle
relaxation is potentiated by inhaled anesthetics,
aminoglycosides and inhaled anesthetics, possibly quinidine
Drugs
d-Tubocurarine
Atracurium
Cisatracurium
Mivacurium a
Rocuronium
Vecuronium
3.Centrally acting
Cyclobenzaprine
Receptor Interactions
Mechanism unknown
Pharmacokinetics
Oral for acute muscle
spasm due to injury or inflammation
Adverse Effects
M block, sedation,
confusion, and ocular effects
Mechanism of Action
Inhibition of spinal stretch reflex
Diazepam
Receptor Interactions
GABA A receptor activation: postsynaptic
Pharmacokinetics
Oral and parenteral for acute and chronic spasms
Mechanism of Action
Facilitates GABA-ergic transmission in CNS
Adverse Effects
Sedation, additive with
other CNS depressants
Baclofen
Pharmacokinetics
Oral; intrathecal for severe spasticity
Receptor Interactions
GABA B receptor
activation: pre- and postsynaptic
Adverse Effects
Sedation, muscle weakness
Mechanism of Action
Facilitates spinal
inhibition of motor neurons
Tizanidine
Mechanism of Action
Pre- and postsynaptic inhibition
Receptor Interactions
α2 Agonist in spinal cord
Pharmacokinetics
Oral for acute and chronic spasms
Adverse Effects
Muscle weakness, sedation, hypotension
4.Direct-acting
Receptor Interactions
Blocks RyR1 Ca2+ channels in skeletal muscle
Pharmacokinetics
Oral for acute and chronic spasms ,IV for malignant hyperthermia
Mechanism of Action
Weakens muscle contraction by reducing myosin-acting interaction
Drugs
Dantrolene
Adverse Effects
Muscle weakness