Muscle Relaxers
SHANNON KEHR
PHYSIOLOGY
APRIL 1, 2014
What is a Muscle Relaxer?
 A muscle relaxer, also
known as a muscle
relaxant, is a drug which
affects skeletal
muscle function and
decreases the muscle
tone. It may be used to
alleviate symptoms such
as muscle spasms, pain.
History of Muscle Relaxers
 The earliest known use of
muscle relaxant drugs
dates back to the 16th
century, when European
explorers encountered
natives of the Amazon were
using poison-tipped arrows
that produced death by
skeletal muscle
paralysis. By 1943,
neuromuscular blocking
drugs became established
as muscle relaxants in the
practice of anesthesia
and surgery.
Muscle Relaxers and the Nervous System
 Muscle relaxers
refer to two major
therapeutic groups:
neuromuscular
blockers
and spasmolytics
Two Therapeutic Muscle Relaxers
Neuromuscular Blockers
Spasmolytics
 Neuromuscular blockers
 Spasmolytics, also
act by interfering with
transmission at the
neuromuscular end plate
and have no central
nervous system activity.
They are often used during
surgical procedures and
in intensive
care and emergency
medicine to cause
temporary paralysis.
known as "centrally
acting" muscle
relaxants, are used to
alleviate
musculoskeletal pain
and spasms and to
reduce spasticity in a
variety of neurological
conditions.
Neuromuscular Blockers
 Most neuromuscular blockers function by blocking transmission at
the end plate of the neuromuscular junction.
 Normal end plate function can be blocked by two mechanisms. Non
depolarizing agents, such as tubocurarine, block the agonist,
acetylcholine, from binding to nicotinic receptors and activating
them, thereby preventing depolarization.
 Alternatively, depolarizing agents, such as succinylcholine, are
nicotinic receptor agonists which mimic Ach, block muscle
contraction by depolarizing to such an extent that it desensitizes the
receptor and it can no longer initiate an action potential and cause
muscle contraction.
 Both of these classes of neuromuscular blocking drugs are
structurally similar to acetylcholine, the endogenous ligand, in
many cases containing two acetylcholine molecules linked end-toend by a rigid carbon ring system, as in pancuronium (a
nondepolarizing agent).
Spasmolytics
 Spasmolytic agents generally work by either enhancing
the level of inhibition, or reducing the level of excitation.
 Inhibition is enhanced by mimicking or enhancing the
actions of endogenous inhibitory substances, such as
gamma-Aminobutyric acid (GABA).
 GABA is the chief inhibitory neurotransmitter in
the mammalian central nervous system. It plays a role in
regulating neuronal excitability throughout the nervous
system. In humans, GABA is also directly responsible for
the regulation of muscle tone.
 Spasmolytics are referred to as “centrally acting muscle
relaxants” because they can be used to target specific
regions of the body such as low back and neck.
Spasmolytics
Types of Muscle Relaxers
 Carisoprodol “Soma”
 Cyclobenzaprine
“Flexeril”
 Diazepam “Valium”
 Metaxalone
“Skelaxin”
 Methocarbamol
“Robaxin”
Side
Effects
•Heart Failure
•Paralysis
•Sedation
•Dizziness
•Headache
•Drowsiness
•Nausea and
Vomiting
•Irritability