Muscle Relaxers - Mechanisms, Indications, Side Effects
Summary
TLDRThis video covers the topic of muscle relaxants, which reduce muscle tone and treat conditions like muscle spasms, hyperreflexia, and pain. Muscle relaxants are divided into neuromuscular blockers and spasmolytics. Neuromuscular blockers work peripherally to induce short-term paralysis during surgery, while spasmolytics act centrally in the brain or spinal cord. The video explains various drugs like diazepam, baclofen, tizanidine, and dantrolene, their mechanisms, and their use in conditions such as multiple sclerosis, cerebral palsy, and spinal cord injuries. It also emphasizes the potential side effects and precautions of these medications.
Takeaways
- 💊 Muscle relaxants decrease muscle tone and are used to treat symptoms such as muscle spasms, hyperreflexia, and pain.
- 🧠 Muscle relaxants are divided into two groups: neuromuscular blockers and spasmolytics. Neuromuscular blockers work at the neuromuscular junction, while spasmolytics act centrally in the brain or spinal cord.
- ⚡ Neuromuscular blockers are used for short-term flaccid paralysis during surgeries and procedures like intubation by blocking nicotinic 1 receptors.
- 💡 Spasmolytics, often referred to as muscle relaxants, are used to treat painful musculoskeletal conditions and disorders like multiple sclerosis and cerebral palsy.
- 🧬 Diazepam, a benzodiazepine, enhances GABA-A receptor activity, increasing chloride permeability in lower motor neurons, causing hyperpolarization and reducing muscle contraction.
- 🦴 Baclofen, used for spinal cord injuries, activates GABA-B receptors, increasing potassium conductance and reducing excitatory neurotransmitter release, leading to muscle relaxation.
- 🔗 Tizanidine is an alpha-2 agonist that decreases the release of excitatory neurotransmitters, used for managing spasms associated with multiple sclerosis.
- ⚙️ Dantrolene, a direct-acting muscle relaxant, blocks ryanodine receptors in skeletal muscles, preventing calcium release and muscle contraction, making it useful for conditions like malignant hyperthermia.
- 🚫 Muscle relaxants acting in the CNS can cause adverse effects like dizziness, fatigue, muscle weakness, and euphoria, with cautions against alcohol use and driving.
- ⚠️ Commonly prescribed muscle relaxants for local spasms include carisoprodol, cyclobenzaprine, and metaxalone, though their mechanisms are not well understood.
Q & A
What are the two major groups of muscle relaxants?
-The two major groups of muscle relaxants are neuromuscular blockers and spasmolytics.
What is the primary function of neuromuscular blockers?
-Neuromuscular blockers block nicotinic 1 receptors at the neuromuscular junction, preventing skeletal muscle contractions, often used during surgeries and intubation to induce short-term flaccid paralysis.
How do spasmolytics work in the body?
-Spasmolytics work primarily in the central nervous system, either at the spinal cord or brain level, to reduce muscle tone and spasms.
What are some common indications for the use of muscle relaxants?
-Muscle relaxants are indicated for treating painful musculoskeletal conditions such as muscle spasms, hyperreflexia, and conditions like multiple sclerosis and cerebral palsy.
How does diazepam work as a muscle relaxant?
-Diazepam, a benzodiazepine, enhances the effect of GABA by increasing chloride permeability in the lower motor neurons, which hyperpolarizes the cell, reducing muscle spasms.
What is the mechanism of action for baclofen?
-Baclofen activates GABA-B receptors, increasing potassium conductance and hyperpolarizing lower motor neurons. It also reduces excitatory neurotransmitter release by decreasing calcium influx in upper motor neurons.
What role does tizanidine play in muscle relaxation?
-Tizanidine is an alpha-2 agonist that reduces excitatory neurotransmitter release, commonly used for managing muscle spasms in conditions like multiple sclerosis.
How does dantrolene differ from other muscle relaxants in terms of its mechanism?
-Dantrolene acts directly on skeletal muscles by blocking ryanodine receptors, preventing calcium release from the sarcoplasmic reticulum, thereby inhibiting muscle contraction.
What is malignant hyperthermia, and how is it treated?
-Malignant hyperthermia is a severe reaction to certain anesthetics, characterized by muscle rigidity and fever. It is treated with dantrolene, which prevents excessive calcium release in muscles.
What are common adverse effects associated with CNS-acting muscle relaxants?
-Common adverse effects include euphoria, dizziness, fatigue, and muscle weakness. Patients should avoid alcohol and be cautious when operating machinery.
Outlines
💊 Overview of Muscle Relaxants
This paragraph introduces muscle relaxants, explaining that they are used to decrease muscle tone and treat symptoms like spasms, hyperreflexia, and pain. Muscle relaxants are categorized into two main groups: neuromuscular blockers and spasmolytics. Neuromuscular blockers act at the neuromuscular junction, causing temporary paralysis, often used in surgeries or intubation. In contrast, spasmolytics act centrally in the brain or spinal cord and are the focus of this discussion. Muscle relaxants are mainly indicated for treating painful musculoskeletal conditions and chronic disorders such as multiple sclerosis and cerebral palsy, working best alongside physical therapy.
🧠 Mechanism of Muscle Relaxants
Here, the focus shifts to the mechanisms by which muscle relaxants function. It starts with a review of motor neuron synapses in the spinal cord. Voluntary muscle contraction involves upper motor neurons (UMNs) from the brain, which activate lower motor neurons (LMNs) to stimulate muscles. Inhibitory interneurons release GABA to dampen LMN excitation, preventing overactivity. Diazepam, a benzodiazepine, enhances GABA's inhibitory effect by increasing chloride ion permeability, further hyperpolarizing LMNs and reducing muscle contractions. The mechanisms of other muscle relaxants such as baclofen, tizanidine, and dantrolene, each with distinct actions on neurotransmitters and receptors, are also described in detail.
💉 Detailed Actions of Specific Muscle Relaxants
This paragraph elaborates on the specific functions of several muscle relaxants. Baclofen, for instance, activates GABA receptors, causing hyperpolarization of LMNs and reducing excitatory neurotransmitter release from UMNs, thus reducing muscle spasms. Tizanidine, used for multiple sclerosis, works as an alpha-2 agonist, decreasing the release of excitatory neurotransmitters. Dantrolene, a direct-acting relaxant, prevents muscle contractions by blocking calcium release in skeletal muscle. It’s particularly useful in treating conditions like malignant hyperthermia and other muscle-related disorders. Unlike other relaxants, dantrolene doesn’t act within the CNS but directly on muscles.
🩺 Common Uses and Side Effects of Muscle Relaxers
This paragraph discusses common muscle relaxants prescribed for local muscle spasms resulting from overexertion or injuries. Cyclobenzaprine, carisoprodol, and others are mentioned, though their exact mechanisms are not well understood. Muscle relaxants that act in the CNS generally share similar side effects such as euphoria, dizziness, fatigue, and muscle weakness. Patients taking these drugs should be monitored and advised not to mix them with alcohol or operate heavy machinery due to their CNS depressant effects.
Mindmap
Keywords
💡Muscle Relaxants
💡Neuromuscular Blockers
💡Spasmolytic Agents
💡Diazepam
💡Baclofen
💡Tizanidine
💡Dantrolene
💡Malignant Hyperthermia (MH)
💡CNS Depressants
💡Motor Neuron Synapses
💡Hyperpolarization
Highlights
Muscle relaxants are divided into two groups: neuromuscular blockers and spasmolytics.
Neuromuscular blockers work peripherally by blocking nicotinic 1 receptors at the neuromuscular junction.
Neuromuscular blockers are used in surgeries and procedures like intubation to cause short-term flaccid paralysis.
Spasmolytics act centrally at the level of the spinal cord or brain.
The term 'muscle relaxants' typically refers to spasmolytics, which are used to treat painful musculoskeletal conditions.
Diazepam, a benzodiazepine, increases the action of GABA by binding to GABA-A receptors and enhancing chloride permeability.
Baclofen activates GABA-B receptors, increasing potassium conductance, which hyperpolarizes neurons and reduces muscle spasms.
Tizanidine, an alpha-2 agonist, reduces the release of excitatory neurotransmitters, helping manage muscle spasms.
Dantrolene is a direct-acting muscle relaxant that blocks ryanodine receptors in skeletal muscles, preventing calcium release.
Dantrolene is used to treat muscle spasms in conditions like multiple sclerosis, cerebral palsy, and malignant hyperthermia.
Malignant hyperthermia is a severe reaction to certain anesthetics and muscle relaxants, characterized by fever and muscle rigidity.
Dantrolene selectively targets skeletal muscle, sparing the heart due to the different types of ryanodine receptors.
Common muscle relaxers for local muscle spasms include carisoprodol, cyclobenzaprine, and metaxalone.
The mechanisms of most CNS-acting muscle relaxers are not fully understood but are thought to involve the brainstem.
Adverse effects of CNS-acting muscle relaxers include euphoria, dizziness, fatigue, and muscle weakness, requiring caution with tasks like driving.
Transcripts
our pharmacology topic today is muscle
relaxants muscle relaxants decrease
muscle tone they are used to treat
symptoms associated with increased
muscle tone such as muscle spasms
hyperreflexia and pain technically the
term muscle relaxants can be subdivided
into two major groups including
neuromuscular blockers and spasmolytic
s' neuromuscular blockers work in the
periphery neuromuscular blockers block
nicotinic 1 receptors in the
neuromuscular Junction to stop skeletal
muscle contractions they are useful
during certain types of surgery and for
procedures such as intubation to cause
short-term flaccid paralysis most
spasmolytic centrally at the level of
the spinal cord or brain the term muscle
relaxants is most often used to refer
just to spasmolytic s' and these are the
topic of this video remember that an
indication is the reason the drug is
used as mentioned muscle relaxants are
often indicated for the treatment of
painful musculoskeletal conditions
some examples include treating muscle
spasms associated with over exertion and
helping manage the spasticity of severe
chronic disorders like multiple
sclerosis and cerebral palsy these drugs
usually work best when used alongside
physical therapy to understand the
mechanisms for the muscle relaxers
diazepam tizen adeana baclofen let's
review a cross-section of the spinal
cord and zoom in on the motor neuron
synapses
for voluntary muscle contraction of
limbs the upper motor neuron or a umn is
activated in the cerebral cortex and
action potentials travel down the spinal
cord or they synapse with lower motor
neurons or elements at the level of exit
inhibitory interneurons regulate the
excitation of the element an action
potential traveling down the upper motor
neuron will cause the release of
excitatory neurotransmitters like
norepinephrine or glutamate onto the lmn
which will then activate the skeletal
muscle the inhibitory neurotransmitter
gaba is released from the inhibitory
neuron and acts to decrease the
excitation of the element by increasing
chloride permeability in the element
diazepam a benzodiazepine used for
muscle spasms will bind to the BZD
binding site of gaba-a receptors located
on cell bodies of the lower motor
neurons to increase the permeability of
chloride even more
thus the action of diazepam augments or
increases the action of GABA and
hyperpolarizes the cell even more the
hyper-polarization decreases the
frequency of action potentials traveling
through the element to the muscle
baclofen is a drug used for spasms
associated with spinal cord injuries
baclofen activates gamma b receptors in
the postsynaptic membrane to cause an
increase in potassium conductance in the
alamin which also causes
hyper-polarization there are also gamma
B receptors in the presynaptic membrane
of the upper motor neuron activation of
these receptors leads to less release of
calcium ions and consequently less
release of excitatory neurotransmitters
like norepinephrine and glutamate from
the umn onto the element consequently
less action potentials travel down the
lmn to reach the muscle ties Anna Dean
is one of the drugs used for spasms
associated with multiple sclerosis this
drug is an alpha-2 agonist and binds to
um
and axon terminals and causes less
release of excitatory neurotransmitter
another muscle relaxer dantrolene is a
direct acting muscle relaxant that
blocks ryanodine receptors in skeletal
muscles therefore unlike the other
muscle relaxants it doesn't act in the
CNS dantrolene is indicated for the
treatment of muscle spasms associated
with multiple sclerosis cerebral palsy
spinal cord injuries and malignant
hyperthermia or mhm mhm is a severe
reaction characterized by fever muscle
rigidity tachycardia although rare mhm
occurs in susceptible individuals that
are exposed to volatile general
anesthetics like halothane and
depolarizing neuromuscular blockers like
succinylcholine dantrolene binds to the
ryanodine channel and prevents it from
opening when the action potential
reaches the D HPR this prevents release
of calcium from the sarcoplasmic
reticulum and prevents muscle
contraction dantrolene is more selective
for skeletal muscle because the heart
has ryouta dean type 2 receptors instead
of type 1 that is in skeletal muscle
several muscle relaxers are used for
local muscle spasms associated with over
exertion or injuries manual laborers or
those in car accidents are examples of
individuals who may have these drugs
prescribed by a physician common muscle
relaxers that fit this category are car
sore / doll cyclobenzaprine Mattacks
alone Clorox is owned and orphan adrene
the mechanism for these drugs is not
well understood but is believed that
they are to act in the brain stem
most relaxers that act in the cns have
the following adverse effects in common
euphoria lightheadedness or dizziness
fatigue and muscle weakness due to these
effects it is important to advise
patience and monitor them while taking
these medications also since most muscle
relaxers are CNS depressants don't mix
with alcohol and use caution when
driving and operating machinery here is
a summary of the mechanisms of action
for muscle relaxers pause the video now
for review here now is a practice
problem to test your knowledge pause the
video and think of your answer
if you answered age then you are correct
thanks for watching
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