A muscle relaxant is a drug that affects
skeletal muscle function and decreases the
muscle tone. It may be used to alleviate symptoms such as muscle
spasm
A spasm is a sudden involuntary contraction of a muscle, a group of muscles, or a hollow organ such as the bladder.
A spasmodic muscle contraction may be caused by many medical conditions, including dystonia. Most commonly, it is a muscle c ...
s,
pain, and
hyperreflexia
Hyperreflexia is overactive or overresponsive bodily reflexes. Examples of this include twitching and spastic tendencies, which indicate upper disease of the upper motor neurons and the lessening or loss of control ordinarily exerted by higher ...
. The term "muscle relaxant" is used to refer to two major therapeutic groups:
neuromuscular blockers
Neuromuscular-blocking drugs block neuromuscular transmission at the neuromuscular junction, causing paralysis of the affected skeletal muscles. This is accomplished via their action on the post-synaptic acetylcholine (Nm) receptors.
In c ...
and
spasmolytics
A muscle relaxant is a drug that affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate symptoms such as muscle spasms, pain, and hyperreflexia. The term "muscle relaxant" is used to refer to two major therapeu ...
. Neuromuscular blockers act by interfering with transmission at the neuromuscular end plate and have no
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
(CNS) activity. They are often used during surgical procedures and in
intensive care
Intensive care medicine, also called critical care medicine, is a medical specialty that deals with seriously or critically ill patients who have, are at risk of, or are recovering from conditions that may be life-threatening. It includes pro ...
and
emergency medicine to cause temporary
paralysis. Spasmolytics, also known as "centrally acting" muscle relaxant, are used to alleviate
musculoskeletal
The human musculoskeletal system (also known as the human locomotor system, and previously the activity system) is an organ system that gives humans the ability to move using their muscular and skeletal systems. The musculoskeletal system prov ...
pain and spasms and to reduce
spasticity
Spasticity () is a feature of altered skeletal muscle performance with a combination of paralysis, increased tendon reflex activity, and hypertonia. It is also colloquially referred to as an unusual "tightness", stiffness, or "pull" of muscles ...
in a variety of
neurological
Neurology (from el, νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the brain, the spinal c ...
conditions. While both neuromuscular blockers and spasmolytics are often grouped together as muscle relaxant,
[Definition of Muscle relaxant]
"
MedicineNet.com
'' (c) 1996–2007. Retrieved on September 19, 2007.[muscle relaxant]
."
mediLexicon
.'' (c) 2007. Retrieved on September 19, 2007. the term is commonly used to refer to spasmolytics only.
[Muscle relaxants]
" ''WebMD
WebMD is an American corporation known primarily as an online publisher of news and information pertaining to human health and well-being. The site includes information pertaining to drugs. It is one of the top healthcare websites.
It was fou ...
.'' Last Updated: February 15, 2006. Retrieved on September 19, 2007.[Skeletal Muscle Relaxant (Oral Route, Parenteral Route)]
" '' Mayo Clinic.'' Last Updated: April 1, 2007. Retrieved on September 19, 2007.
History
The earliest known use of muscle relaxant drugs was by natives of the
Amazon Basin in South America who used
poison-tipped
arrows that produced death by skeletal muscle paralysis. This was first documented in the 16th century, when European explorers encountered it. This poison, known today as
curare
Curare ( /kʊˈrɑːri/ or /kjʊˈrɑːri/; ''koo-rah-ree'' or ''kyoo-rah-ree'') is a common name for various alkaloid arrow poisons originating from plant extracts. Used as a paralyzing agent by indigenous peoples in Central and South ...
, led to some of the earliest scientific studies in
pharmacology. Its active ingredient,
tubocurarine
Tubocurarine (also known as ''d''-tubocurarine or DTC) is a toxic alkaloid historically known for its use as an arrow poison. In the mid-1900s, it was used in conjunction with an anesthetic to provide skeletal muscle relaxation during surgery or ...
, as well as many synthetic derivatives, played a significant role in scientific experiments to determine the function of
acetylcholine in
neuromuscular transmission.
By 1943, neuromuscular blocking drugs became established as muscle relaxants in the practice of
anesthesia and
surgery.
The U.S.
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
(FDA) approved the use of
carisoprodol in 1959,
metaxalone
Metaxalone, sold under the brand name Skelaxin, is a muscle relaxant medication used to relax muscles and relieve pain caused by strains, sprains, and other musculoskeletal conditions. Its exact mechanism of action is not known, but it may be du ...
in August 1962, and
cyclobenzaprine in August 1977.
Other skeletal muscle relaxants of that type used around the world come from a number of drug categories and other drugs used primarily for this indication include
orphenadrine (anticholinergic),
chlorzoxazone
Chlorzoxazone ( INN) is a centrally acting muscle relaxant used to treat muscle spasm and the resulting pain or discomfort. It can also be administered for acute pain in general and for tension headache (muscle contraction headache). It acts on t ...
,
tizanidine
Tizanidine, sold under the brand name Zanaflex among others, is a medication that is used to treat muscle spasticity due to spinal cord injury or multiple sclerosis as well as spastic cerebral palsy. Effectiveness appears similar to baclofen ...
(
clonidine relative),
diazepam
Diazepam, first marketed as Valium, is a medicine of the benzodiazepine family that acts as an anxiolytic. It is commonly used to treat a range of conditions, including anxiety, seizures, alcohol withdrawal syndrome, muscle spasms, insomnia, ...
,
tetrazepam and other
benzodiazepines,
mephenoxalone
Mephenoxalone (trade names Dorsiflex, Moderamin, Control-OM) is a muscle relaxant and mild anxiolytic. MIMSMephenoxalone/ref> It inhibits neuron transmission, relaxing skeletal muscles by inhibiting the reflex arc. As the effect of muscle relaxat ...
,
methocarbamol
Methocarbamol, sold under the brand name Robaxin among others, is a medication used for short-term musculoskeletal pain. It may be used together with rest, physical therapy, and pain medication. It is less preferred in low back pain. It has l ...
,
dantrolene
Dantrolene sodium, sold under the brand name Dantrium among others, is a postsynaptic muscle relaxant that lessens excitation-contraction coupling in muscle cells. It achieves this by inhibiting Ca2+ ions release from sarcoplasmic reticulum s ...
,
baclofen
Baclofen, sold under the brand name Lioresal among others, is a medication used to treat muscle spasticity such as from a spinal cord injury or multiple sclerosis. It may also be used for hiccups and muscle spasms near the end of life. It is ta ...
,
Drugs once but no longer or very rarely used to relax skeletal muscles include
meprobamate
Meprobamate—marketed as Miltown by Wallace Laboratories and Equanil by Wyeth, among others—is a carbamate derivative used as an anxiolytic drug. It was the best-selling minor tranquilizer for a time, but has largely been replaced by the be ...
,
barbiturates,
methaqualone
Methaqualone is a hypnotic sedative. It was sold under the brand names Quaalude ( ) and Sopor among others, which contained 300 mg of methaqualone, and sold as a combination drug under the brand name Mandrax, which contained 250 mg me ...
,
glutethimide and the like; some subcategories of opioids have muscle relaxant properties, and some are marketed in combination drugs with skeletal and/or smooth muscle relaxants such as whole
opium products, some
ketobemidone
Ketobemidone, sold under the brand name Ketogan among others, is a powerful synthetic opioid painkiller. Its effectiveness against pain is in the same range as morphine, and it also has some NMDA-antagonist properties imparted, in part, by its m ...
,
piritramide and
fentanyl
Fentanyl, also spelled fentanil, is a very potent synthetic opioid used as a pain medication. Together with other drugs, fentanyl is used for anesthesia. It is also used illicitly as a recreational drug, sometimes mixed with heroin, cocain ...
preparations and
Equagesic
Aspirin/ meprobamate (trade name Equagesic ) is a combination drug indicated for short-term pain treatment accompanied by tension or anxiety in patients with musculoskeletal disorders or tension headache.
Adverse effects
Combinations
The ...
.
Neuromuscular blockers
Muscle relaxation and paralysis can theoretically occur by interrupting function at several sites, including the
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...
,
myelin
Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can be ...
ated somatic nerves, unmyelinated motor nerve terminals,
nicotinic acetylcholine receptor
Nicotinic acetylcholine receptors, or nAChRs, are receptor polypeptides that respond to the neurotransmitter acetylcholine. Nicotinic receptors also respond to drugs such as the agonist nicotine. They are found in the central and peripheral ner ...
s, the motor end plate, and the muscle membrane or contractile apparatus. Most neuromuscular blockers function by blocking transmission at the end plate of the
neuromuscular junction. Normally, a nerve impulse arrives at the motor nerve terminal, initiating an influx of
calcium
Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
ions, which causes the
exocytosis of
synaptic vesicles
In a neuron, synaptic vesicles (or neurotransmitter vesicles) store various neurotransmitters that are released at the synapse. The release is regulated by a voltage-dependent calcium channel. Vesicles are essential for propagating nerve impulse ...
containing
acetylcholine. Acetylcholine then diffuses across the synaptic cleft. It may be hydrolysed by
acetylcholine esterase
Acetylcholinesterase (HGNC symbol ACHE; EC 3.1.1.7; systematic name acetylcholine acetylhydrolase), also known as AChE, AChase or acetylhydrolase, is the primary cholinesterase in the body. It is an enzyme that catalyzes the breakdown of acet ...
(AchE) or bind to the nicotinic receptors located on the motor end plate. The binding of two acetylcholine molecules results in a
conformational change in the receptor that opens the sodium-potassium channel of the nicotinic receptor. This allows and ions to enter the cell and ions to leave the cell, causing a depolarization of the end plate, resulting in muscle contraction. Following depolarization, the acetylcholine molecules are then removed from the end plate region and enzymatically hydrolysed by acetylcholinesterase.
Normal
end plate function can be blocked by two mechanisms. Nondepolarizing agents, such as
tubocurarine
Tubocurarine (also known as ''d''-tubocurarine or DTC) is a toxic alkaloid historically known for its use as an arrow poison. In the mid-1900s, it was used in conjunction with an anesthetic to provide skeletal muscle relaxation during surgery or ...
, block the
agonist, acetylcholine, from binding to nicotinic receptors and activating them, thereby preventing depolarization. Alternatively, depolarizing agents, such as
succinylcholine
Suxamethonium chloride, also known as suxamethonium or succinylcholine, or simply sux by medical abbreviation, is a medication used to cause short-term paralysis as part of general anesthesia. This is done to help with tracheal intubation or ele ...
, 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
An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, ...
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-to-end by a rigid carbon ring system, as in
pancuronium
Pancuronium (trademarked as Pavulon) is an aminosteroid muscle relaxant with various medical uses. It is used in euthanasia and is used in some states as the second of three drugs administered during lethal injections in the United States.
Mec ...
(a nondepolarizing agent).
Spasmolytics
The generation of the
neuronal signals in motor neurons that cause muscle contractions is dependent on the balance of synaptic excitation and inhibition the motor neuron receives. 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
GABA.
Terminology
Because they may act at the level of the cortex, brain stem, or spinal cord, or all three areas, they have traditionally been referred to as "centrally acting" muscle relaxants. However, it is now known not every agent in this class has CNS activity (e.g.
dantrolene
Dantrolene sodium, sold under the brand name Dantrium among others, is a postsynaptic muscle relaxant that lessens excitation-contraction coupling in muscle cells. It achieves this by inhibiting Ca2+ ions release from sarcoplasmic reticulum s ...
), so this name is inaccurate.
Most sources still use the term "centrally acting muscle relaxant". According to
MeSH
A mesh is a barrier made of connected strands of metal, fiber, or other flexible or ductile materials. A mesh is similar to a web or a net in that it has many attached or woven strands.
Types
* A plastic mesh may be extruded, oriented, exp ...
, dantrolene is usually classified as a centrally acting muscle relaxant. The
World Health Organization
The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...
, in its
ATC, uses the term "centrally acting agents", but adds a distinct category of "directly acting agents", for dantrolene. Use of this terminology dates back to at least 1973.
The term "spasmolytic" is also considered a synonym for
antispasmodic
An antispasmodic (synonym: spasmolytic) is a pharmaceutical drug or other agent that suppresses muscle spasms.
Smooth muscle spasm
One type of antispasmodics is used for smooth muscle relaxation, especially in tubular organs of the gastrointest ...
.
Clinical use
Spasmolytics such as
carisoprodol,
cyclobenzaprine,
metaxalone
Metaxalone, sold under the brand name Skelaxin, is a muscle relaxant medication used to relax muscles and relieve pain caused by strains, sprains, and other musculoskeletal conditions. Its exact mechanism of action is not known, but it may be du ...
, and
methocarbamol
Methocarbamol, sold under the brand name Robaxin among others, is a medication used for short-term musculoskeletal pain. It may be used together with rest, physical therapy, and pain medication. It is less preferred in low back pain. It has l ...
are commonly prescribed for
low back pain
Low back pain (LBP) or lumbago is a common disorder involving the muscles, nerves, and bones of the back, in between the lower edge of the ribs and the lower fold of the buttocks. Pain can vary from a dull constant ache to a sudden sharp feel ...
or
neck pain
Neck pain, also known as cervicalgia, is a common problem, with two-thirds of the population having neck pain at some point in their lives.
Neck pain, although felt in the neck, can be caused by numerous other spinal problems. Neck pain may arise ...
,
fibromyalgia,
tension headaches
Tension headache, also known as stress headache, or tension-type headache (TTH), is the most common type of primary headache. The pain can radiate from the lower back of the head, the neck, eyes or other muscle groups in the body typically affecti ...
and
myofascial pain syndrome.
However, they are not recommended as first-line agents; in acute low back pain, they are not more effective than
paracetamol or nonsteroidal anti-inflammatory drugs (
NSAID
Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...
s),
and in fibromyalgia they are not more effective than
antidepressants
Antidepressants are a class of medication used to treat major depressive disorder, anxiety disorders, chronic pain conditions, and to help manage addictions. Common side-effects of antidepressants include dry mouth, weight gain, dizziness, hea ...
.
Nevertheless, some (low-quality) evidence suggests muscle relaxants can add benefit to treatment with NSAIDs.
In general, no high-quality
evidence supports their use.
No drug has been shown to be better than another, and all of them have
adverse effects
An adverse effect is an undesired harmful effect resulting from a medication or other intervention, such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. The term complica ...
, particularly
dizziness
Dizziness is an imprecise term that can refer to a sense of disorientation in space, vertigo, or lightheadedness. It can also refer to disequilibrium or a non-specific feeling, such as giddiness or foolishness.
Dizziness is a common medical c ...
and
drowsiness
Somnolence (alternatively sleepiness or drowsiness) is a state of strong desire for sleep, or sleeping for unusually long periods (compare hypersomnia). It has distinct meanings and causes. It can refer to the usual state preceding falling asleep ...
.
Concerns about possible abuse and
interaction
Interaction is action that occurs between two or more objects, with broad use in philosophy and the sciences. It may refer to:
Science
* Interaction hypothesis, a theory of second language acquisition
* Interaction (statistics)
* Interactions o ...
with other drugs, especially if increased sedation is a risk, further limit their use.
A muscle relaxant is chosen based on its adverse-effect profile, tolerability, and cost.
Muscle relaxants (according to one study) were not advised for
orthopedic
Orthopedic surgery or orthopedics ( alternatively spelt orthopaedics), is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat musculoskeletal ...
conditions, but rather for
neurological
Neurology (from el, νεῦρον (neûron), "string, nerve" and the suffix -logia, "study of") is the branch of medicine dealing with the diagnosis and treatment of all categories of conditions and disease involving the brain, the spinal c ...
conditions such as spasticity in
cerebral palsy
Cerebral palsy (CP) is a group of movement disorders that appear in early childhood. Signs and symptoms vary among people and over time, but include poor coordination, stiff muscles, weak muscles, and tremors. There may be problems with sens ...
and
multiple sclerosis.
Dantrolene, although thought of primarily as a peripherally acting agent, is associated with CNS effects, whereas baclofen activity is strictly associated with the CNS.
Muscle relaxants are thought to be useful in painful disorders based on the theory that pain induces spasm and spasm causes pain. However, considerable evidence contradicts this theory.
In general, muscle relaxants are not approved by FDA for long-term use. However,
rheumatologists
Rheumatology (Greek ''ῥεῦμα'', ''rheûma'', flowing current) is a branch of medicine devoted to the diagnosis and management of disorders whose common feature is inflammation in the bones, muscles, joints, and internal organs. Rheumatolog ...
often prescribe
cyclobenzaprine nightly on a daily basis to increase stage 4 sleep. By increasing this sleep stage, patients feel more refreshed in the morning. Improving sleep is also beneficial for patients who have fibromyalgia.
Muscle relaxants such as
tizanidine
Tizanidine, sold under the brand name Zanaflex among others, is a medication that is used to treat muscle spasticity due to spinal cord injury or multiple sclerosis as well as spastic cerebral palsy. Effectiveness appears similar to baclofen ...
are prescribed in the treatment of
tension headaches
Tension headache, also known as stress headache, or tension-type headache (TTH), is the most common type of primary headache. The pain can radiate from the lower back of the head, the neck, eyes or other muscle groups in the body typically affecti ...
.
Diazepam
Diazepam, first marketed as Valium, is a medicine of the benzodiazepine family that acts as an anxiolytic. It is commonly used to treat a range of conditions, including anxiety, seizures, alcohol withdrawal syndrome, muscle spasms, insomnia, ...
and
carisoprodol are not recommended for older adults,
pregnant women
Pregnancy is the time during which one or more offspring develops ( gestates) inside a woman's uterus (womb). A multiple pregnancy involves more than one offspring, such as with twins.
Pregnancy usually occurs by sexual intercourse, but ca ...
, or people who have depression or for those with a history of drug or alcohol
addiction
Addiction is a neuropsychological disorder characterized by a persistent and intense urge to engage in certain behaviors, one of which is the usage of a drug, despite substantial harm and other negative consequences. Repetitive drug use o ...
.
Mechanism
Because of the enhancement of inhibition in the CNS, most spasmolytic agents have the side effects of sedation and drowsiness and may cause dependence with long-term use. Several of these agents also have abuse potential, and their prescription is strictly controlled.
The
benzodiazepines, such as
diazepam
Diazepam, first marketed as Valium, is a medicine of the benzodiazepine family that acts as an anxiolytic. It is commonly used to treat a range of conditions, including anxiety, seizures, alcohol withdrawal syndrome, muscle spasms, insomnia, ...
, interact with the
GABAA receptor in the central nervous system. While it can be used in patients with muscle spasm of almost any origin, it produces sedation in most individuals at the doses required to reduce muscle tone.
Baclofen
Baclofen, sold under the brand name Lioresal among others, is a medication used to treat muscle spasticity such as from a spinal cord injury or multiple sclerosis. It may also be used for hiccups and muscle spasms near the end of life. It is ta ...
is considered to be at least as effective as diazepam in reducing spasticity, and causes much less sedation. It acts as a GABA
agonist at GABA
B receptors in the brain and spinal cord, resulting in hyperpolarization of neurons expressing this receptor, most likely due to increased potassium ion conductance. Baclofen also inhibits neural function presynaptically, by reducing calcium ion influx, and thereby reducing the release of excitatory neurotransmitters in both the brain and spinal cord. It may also reduce pain in patients by inhibiting the release of
substance P
Substance P (SP) is an undecapeptide (a peptide composed of a chain of 11 amino acid residues) and a member of the tachykinin neuropeptide family. It is a neuropeptide, acting as a neurotransmitter and as a neuromodulator. Substance P and its clo ...
in the spinal cord, as well.
Clonidine and other imidazoline compounds have also been shown to reduce muscle spasms by their central nervous system activity.
Tizanidine
Tizanidine, sold under the brand name Zanaflex among others, is a medication that is used to treat muscle spasticity due to spinal cord injury or multiple sclerosis as well as spastic cerebral palsy. Effectiveness appears similar to baclofen ...
is perhaps the most thoroughly studied clonidine analog, and is an agonist at
α2-adrenergic receptors, but reduces spasticity at doses that result in significantly less
hypotension
Hypotension is low blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries as the heart pumps out blood. Blood pressure is indicated by two numbers, the systolic blood pressure (the top number) and the dia ...
than clonidine.
Neurophysiologic studies show that it depresses excitatory feedback from muscles that would normally increase muscle tone, therefore minimizing spasticity.
Furthermore, several clinical trials indicate that tizanidine has a similar efficacy to other spasmolytic agents, such as diazepam and baclofen, with a different spectrum of adverse effects.
The
hydantoin derivative
dantrolene
Dantrolene sodium, sold under the brand name Dantrium among others, is a postsynaptic muscle relaxant that lessens excitation-contraction coupling in muscle cells. It achieves this by inhibiting Ca2+ ions release from sarcoplasmic reticulum s ...
is a spasmolytic agent with a unique mechanism of action outside of the CNS. It reduces skeletal muscle strength by inhibiting the excitation-contraction coupling in the
muscle fiber
A muscle cell is also known as a myocyte when referring to either a cardiac muscle cell (cardiomyocyte), or a smooth muscle cell as these are both small cells. A skeletal muscle cell is long and threadlike with many nuclei and is called a muscl ...
. In normal muscle contraction, calcium is released from the
sarcoplasmic reticulum
The sarcoplasmic reticulum (SR) is a membrane-bound structure found within muscle cells that is similar to the smooth endoplasmic reticulum in other cells. The main function of the SR is to store calcium ions (Ca2+). Calcium ion levels are ke ...
through the
ryanodine receptor channel, which causes the tension-generating interaction of
actin
Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils. It is found in essentially all eukaryotic cells, where it may be present at a concentration of ov ...
and
myosin. Dantrolene interferes with the release of calcium by binding to the ryanodine receptor and blocking the endogenous ligand ryanodine by
competitive inhibition
Competitive inhibition is interruption of a chemical pathway owing to one chemical substance inhibiting the effect of another by competing with it for binding or bonding. Any metabolic or chemical messenger system can potentially be affected b ...
. Muscle that contracts more rapidly is more sensitive to dantrolene than muscle that contracts slowly, although
cardiac muscle
Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle th ...
and
smooth muscle are depressed only slightly, most likely because the release of calcium by their sarcoplasmic reticulum involves a slightly different process. Major adverse effects of dantrolene include general muscle weakness, sedation, and occasionally
hepatitis
Hepatitis is inflammation of the liver tissue. Some people or animals with hepatitis have no symptoms, whereas others develop yellow discoloration of the skin and whites of the eyes ( jaundice), poor appetite, vomiting, tiredness, abdominal ...
.
Other common spasmolytic agents include:
methocarbamol
Methocarbamol, sold under the brand name Robaxin among others, is a medication used for short-term musculoskeletal pain. It may be used together with rest, physical therapy, and pain medication. It is less preferred in low back pain. It has l ...
,
carisoprodol,
chlorzoxazone
Chlorzoxazone ( INN) is a centrally acting muscle relaxant used to treat muscle spasm and the resulting pain or discomfort. It can also be administered for acute pain in general and for tension headache (muscle contraction headache). It acts on t ...
,
cyclobenzaprine,
gabapentin
Gabapentin, sold under the brand name Neurontin among others, is an anticonvulsant medication primarily used to treat partial seizures and neuropathic pain. It is a first-line medication for the treatment of neuropathic pain caused by diabeti ...
,
metaxalone
Metaxalone, sold under the brand name Skelaxin, is a muscle relaxant medication used to relax muscles and relieve pain caused by strains, sprains, and other musculoskeletal conditions. Its exact mechanism of action is not known, but it may be du ...
, and
orphenadrine.
Thiocolchicoside is a muscle relaxant with
anti-inflammatory
Anti-inflammatory is the property of a substance or treatment that reduces inflammation or swelling. Anti-inflammatory drugs, also called anti-inflammatories, make up about half of analgesics. These drugs remedy pain by reducing inflammation as o ...
and
analgesic effects and an unknown mechanism of action.
It acts as a
competitive antagonist
A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of r ...
at
GABAA and
glycine receptors
The glycine receptor (abbreviated as GlyR or GLR) is the receptor of the amino acid neurotransmitter glycine. GlyR is an ionotropic receptor that produces its effects through chloride current. It is one of the most widely distributed inhibitory ...
with similar
potencies, as well as at
nicotinic acetylcholine receptor
Nicotinic acetylcholine receptors, or nAChRs, are receptor polypeptides that respond to the neurotransmitter acetylcholine. Nicotinic receptors also respond to drugs such as the agonist nicotine. They are found in the central and peripheral ner ...
s, albeit to a much lesser extent.
It has powerful
proconvulsant activity and should not be used in
seizure
An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with l ...
-prone individuals.
Side effects
Patients most commonly report
sedation as the main adverse effect of muscle relaxants. Usually, people become less alert when they are under the effects of these drugs. People are normally advised not to drive
vehicles
A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), ...
or operate
heavy machinery
Heavy equipment or heavy machinery refers to heavy-duty vehicles specially designed to execute construction tasks, most frequently involving earthwork operations or other large construction tasks. ''Heavy equipment'' usually comprises five e ...
while under muscle relaxants' effects.
Cyclobenzaprine produces confusion and
lethargy
Lethargy is a state of tiredness, sleepiness, weariness, fatigue, sluggishness or lack of energy. It can be accompanied by depression, decreased motivation, or apathy. Lethargy can be a normal response to inadequate sleep, overexertion, overwo ...
, as well as
anticholinergic
Anticholinergics (anticholinergic agents) are substances that block the action of the neurotransmitter called acetylcholine (ACh) at synapses in the central and peripheral nervous system.
These agents inhibit the parasympathetic nervous sys ...
side effects. When taken in excess or in combination with other substances, it may also be
toxic
Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...
. While the body adjusts to this medication, it is possible for patients to experience
dry mouth
Xerostomia, also known as dry mouth, is dryness in the mouth, which may be associated with a change in the composition of saliva, or reduced salivary flow, or have no identifiable cause.
This symptom is very common and is often seen as a side eff ...
,
fatigue, lightheadedness,
constipation
Constipation is a bowel dysfunction that makes bowel movements infrequent or hard to pass. The stool is often hard and dry. Other symptoms may include abdominal pain, bloating, and feeling as if one has not completely passed the bowel movement ...
or
blurred vision. Some serious but unlikely side effects may be experienced, including mental or mood changes, possible confusion and
hallucinations, and difficulty urinating. In a very few cases, very serious but rare side effects may be experienced: irregular heartbeat, yellowing of eyes or skin,
fainting
Syncope, commonly known as fainting, or passing out, is a loss of consciousness and muscle strength characterized by a fast onset, short duration, and spontaneous recovery. It is caused by a decrease in blood flow to the brain, typically from ...
,
abdominal pain
Abdominal pain, also known as a stomach ache, is a symptom associated with both non-serious and serious medical issues.
Common causes of pain in the abdomen include gastroenteritis and irritable bowel syndrome. About 15% of people have a m ...
including
stomach ache
Abdominal pain, also known as a stomach ache, is a symptom associated with both non-serious and serious medical issues.
Common causes of pain in the abdomen include gastroenteritis and irritable bowel syndrome. About 15% of people have a m ...
,
nausea
Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of the ...
or
vomiting
Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose.
Vomiting can be the result of ailments like food poisoning, gastroenteri ...
,
lack of appetite
Anorexia is a medical term for a loss of appetite. While the term in non-scientific publications is often used interchangeably with anorexia nervosa, many possible causes exist for a loss of appetite, some of which may be harmless, while others i ...
, seizures, dark urine or loss of coordination.
Patients taking carisoprodol for a prolonged time have reported
dependence,
withdrawal
Withdrawal means "an act of taking out" and may refer to:
* Anchoresis (withdrawal from the world for religious or ethical reasons)
* ''Coitus interruptus'' (the withdrawal method)
* Drug withdrawal
* Social withdrawal
* Taking of money from a ban ...
and abuse, although most of these cases were reported by patients with addiction history. These effects were also reported by patients who took it in combination with other drugs with abuse potential, and in fewer cases, reports of carisoprodol-associated abuse appeared when used without other drugs with abuse potential.
Common side effects eventually caused by metaxalone include dizziness,
headache, drowsiness, nausea,
irritability
Irritability (also called as crankiness) is the excitatory ability that living organisms have to respond to changes in their environment. The term is used for both the physiological reaction to stimuli and for the pathological, abnormal or excessi ...
,
nervousness
Nervous may refer to:
* nervousness
* Nervous system, a network of cells in an animal's body that coordinates movement and the senses
** Nervous tissue, the cells of the nervous system that work in aggregate to transmit signals
Music
* "Nervous" ...
,
upset stomach
Abdominal pain, also known as a stomach ache, is a symptom associated with both non-serious and serious medical issues.
Common causes of pain in the abdomen include gastroenteritis and irritable bowel syndrome. About 15% of people have a more ...
and
vomiting
Vomiting (also known as emesis and throwing up) is the involuntary, forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose.
Vomiting can be the result of ailments like food poisoning, gastroenteri ...
. Severe side effects may be experienced when consuming metaxalone, such as severe
allergic reactions
Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derm ...
(
rash
A rash is a change of the human skin which affects its color, appearance, or texture.
A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, c ...
,
hives,
itching
Itch (also known as pruritus) is a Wikt:sensation, sensation that causes the desire or reflex to scratch. Itch has resisted many attempts to be classified as any one type of Sensory system, sensory experience. Itch has many similarities to pain, ...
, difficulty breathing, tightness in the chest, swelling of the mouth, face, lips, or tongue),
chills,
fever
Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...
, and
sore throat
Sore throat, also known as throat pain, is pain or irritation of the throat. Usually, causes of sore throat include
* viral infections
* group A streptococcal infection (GAS) bacterial infection
* pharyngitis (inflammation of the throat)
* to ...
, may require medical attention. Other severe side effects include unusual or severe tiredness or weakness, as well as yellowing of the skin or the eyes. When baclofen is administered
intrathecally
Intrathecal administration is a route of administration for drugs via an injection into the spinal canal, or into the subarachnoid space so that it reaches the cerebrospinal fluid (CSF) and is useful in spinal anesthesia, chemotherapy, or pain ...
, it may cause CNS depression accompanied with cardiovascular collapse and
respiratory failure
Respiratory failure results from inadequate gas exchange by the respiratory system, meaning that the arterial oxygen, carbon dioxide, or both cannot be kept at normal levels. A drop in the oxygen carried in the blood is known as hypoxemia; a rise ...
. Tizanidine may lower
blood pressure. This effect can be controlled by administering a low dose at the beginning and increasing it gradually.
See also
*
Paralysis
*
Quaternary ammonium muscle relaxants
Neuromuscular-blocking drugs block neuromuscular transmission at the neuromuscular junction, causing paralysis of the affected skeletal muscles. This is accomplished via their action on the post-synaptic acetylcholine (Nm) receptors.
In clin ...
*
Caroverine
Caroverine (Spasmium, Tinnitin, Tinnex) is a muscle-relaxing drug used in Austria and Switzerland to relieve spasms in smooth muscles (which include intestines, arteries, and other organs), and the use in those countries was extended to aid wi ...
References
External links
*
{{DEFAULTSORT:Muscle Relaxant