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Skeletal muscle relaxant (Oral route, parenteral route)

Brand Names:

  • Amrix
  • Flexeril
  • Lioresal
  • Norflex
  • Orfro
  • Parafon Forte DSC
  • Remular-S
  • Robaxin
  • Robaxin-750
  • Skelaxin
  • Soma
  • Vanadom
  • Zanaflex
  • Lioresal Double Strength

Dosage Forms:

  • Tablet, Extended Release
  • Tablet
  • Capsule
  • Capsule, Extended Release

Uses of This Medicine:

Skeletal muscle relaxants are used to relax certain muscles in your body and relieve the stiffness, pain, and discomfort caused by strains, sprains, or other injury to your muscles. However, these medicines do not take the place of rest, exercise or physical therapy, or other treatment that your doctor may recommend for your medical problem. Methocarbamol also has been used to relieve some of the muscle problems caused by tetanus.

Skeletal muscle relaxants act in the central nervous system (CNS) to produce their muscle relaxant effects. Their actions in the CNS may also produce some of their side effects.

These medicines are available only with your doctor's prescription. In Canada, some of these medicines are available without a prescription.

Before Using This Medicine:


Tell your doctor if you have ever had any unusual or allergic reaction to medicines in this group or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.


Studies with the skeletal muscle relaxants have been done only in adult patients, and there is no specific information comparing use of these medicines in children with use in other age groups. However, carisoprodol and chlorzoxazone have been used in children. They have not been reported to cause different side effects or problems in children than they do in adults.

Older adults

Many medicines have not been tested in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people. There is no specific information about the use of skeletal muscle relaxants in the elderly.


Although skeletal muscle relaxants have not been shown to cause birth defects or other problems, studies on birth defects have not been done in pregnant women. Studies in animals with metaxalone have not shown that it causes birth defects.


Carisoprodol passes into the breast milk and may cause drowsiness or stomach upset in nursing babies. It is not known whether chlorphenesin, chlorzoxazone, metaxalone, or methocarbamol passes into the breast milk. However, these medicines have not been reported to cause problems in nursing babies.

Other medicines

Using medicines in this class with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

  • Adinazolam
  • Alfentanil
  • Alprazolam
  • Amobarbital
  • Anileridine
  • Aprobarbital
  • Bromazepam
  • Brotizolam
  • Butabarbital
  • Butalbital
  • Carisoprodol
  • Chloral Hydrate
  • Chlordiazepoxide
  • Chlorzoxazone
  • Clobazam
  • Clonazepam
  • Clorazepate
  • Codeine
  • Dantrolene
  • Diazepam
  • Estazolam
  • Ethchlorvynol
  • Fentanyl
  • Flunitrazepam
  • Flurazepam
  • Halazepam
  • Hydrocodone
  • Hydromorphone
  • Ketazolam
  • Levorphanol
  • Lorazepam
  • Lormetazepam
  • Medazepam
  • Meperidine
  • Mephenesin
  • Mephobarbital
  • Meprobamate
  • Metaxalone
  • Methocarbamol
  • Methohexital
  • Midazolam
  • Morphine
  • Morphine Sulfate Liposome
  • Nitrazepam
  • Nordazepam
  • Oxazepam
  • Oxycodone
  • Oxymorphone
  • Pentobarbital
  • Phenobarbital
  • Prazepam
  • Primidone
  • Propoxyphene
  • Quazepam
  • Remifentanil
  • Secobarbital
  • Sodium Oxybate
  • Sufentanil
  • Temazepam
  • Thiopental
  • Triazolam

Other interactions

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other medical problems

The presence of other medical problems may affect the use of medicines in this class. Make sure you tell your doctor if you have any other medical problems, especially:

  • Allergies, history of, or
  • Blood disease caused by an allergy or reaction to any other medicine, history of, or
  • Drug abuse or dependence, or history of, or
  • Kidney disease or
  • Liver disease or
  • Porphyria Depending on which of the skeletal muscle relaxants you take, the chance of side effects may be increased; your doctor can choose a muscle relaxant that is less likely to cause problems.
  • Epilepsy Convulsions may be more likely to occur if methocarbamol is given by injection.

Proper Use of This Medicine:

Chlorzoxazone, metaxalone, or methocarbamol tablets may be crushed and mixed with a little food or liquid if needed to make the tablets easier to swallow.


The dose medicines in this class will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of these medicines. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For oral dosage form (tablets):
    • For relaxing stiff, sore muscles:
      • Adults and teenagers 350 milligrams (mg) four times a day.
      • Children 5 to 12 years of age 6.25 mg per kilogram (2.5 mg per pound) of body weight four times a day.
      • Children up to 5 years of age Dose must be determined by your doctor.
  • For oral dosage form (tablets):
    • For relaxing stiff, sore muscles:
      • Adults and teenagers 800 milligrams (mg) three times a day, at first. Your doctor may decrease your dose after you begin to feel better.
      • Children Use and dose must be determined by your doctor.
  • For oral dosage form (tablets):
    • For relaxing stiff, sore muscles:
      • Adults and teenagers 500 milligrams (mg) three or four times a day.
      • Children 125 to 500 mg three or four times a day, depending on the child's size and weight.
  • For oral dosage form (tablets):
    • For relaxing stiff, sore muscles:
      • Adults and teenagers 800 milligrams (mg) three or four times a day.
      • Children Use and dose must be determined by your doctor.
  • For oral dosage form (tablets):
    • For relaxing stiff, sore muscles:
      • Adults and teenagers 1500 milligrams (mg) four times a day, at first. Your doctor may decrease your dose after you begin to feel better.
      • Children Use and dose must be determined by your doctor.
  • For injection dosage form:
    • For relaxing stiff, sore muscles:
      • Adults and teenagers 1 to 3 grams a day, injected into a muscle or a vein. This total daily dose may be divided into smaller amounts that are given several times a day, especially when the medicine is injected into a muscle.
      • Children Use and dose must be determined by your doctor.

Missed dose

If you miss a dose of this medicine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double doses.


Keep out of the reach of children.

Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Keep from freezing.

Do not keep outdated medicine or medicine no longer needed.

Precautions While Using This Medicine:

If you will be taking this medicine for a long time (for example, more than a few weeks), your doctor should check your progress at regular visits.

This medicine will add to the effects of alcohol and other CNS depressants (medicines that slow down the nervous system, possibly causing drowsiness). Some examples of CNS depressants are antihistamines or medicine for hay fever, other allergies, or colds; sedatives, tranquilizers, or sleeping medicine; prescription pain medicine or narcotics; barbiturates; medicine for seizures; other muscle relaxants; or anesthetics, including some dental anesthetics. Do not drink alcoholic beverages, and check with your doctor before taking any of the medicines listed above, while you are using this medicine.

Skeletal muscle relaxants may cause blurred vision or clumsiness or unsteadiness in some people. They may also cause some people to feel drowsy, dizzy, lightheaded, faint, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or are not alert, well-coordinated, and able to see well.

For diabetic patients:

  • Metaxalone (e.g., Skelaxin) may cause false test results with one type of test for sugar in your urine. If your urine sugar test shows an unusually large amount of sugar, or if you have any questions about this, check with your health care professional. This is especially important if your diabetes is not well controlled.

Side Effects of This Medicine:

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

Less common
fast heartbeat
hive-like swellings (large) on face, eyelids, mouth, lips, and/or tongue
mental depression
shortness of breath, troubled breathing, tightness in chest, and/or wheezing
skin rash, hives, itching, or redness
slow heartbeat (methocarbamol injection only)
stinging or burning of eyes
stuffy nose and red or bloodshot eyes
Blood in urine
bloody or black, tarry stools
convulsions (seizures) (methocarbamol injection only)
cough or hoarseness
fast or irregular breathing
lower back or side pain
muscle cramps or pain (not present before treatment or more painful than before treatment)
painful or difficult urination
pain, tenderness, heat, redness, or swelling over a blood vessel (vein) in arm or leg (methocarbamol injection only)
pinpoint red spots on skin
puffiness or swelling of the eyelids or around the eyes
sores, ulcers, or white spots on lips or in mouth
sore throat and fever with or without chills
swollen and/or painful glands
unusual bruising or bleeding
unusual tiredness or weakness
vomiting of blood or material that looks like coffee grounds
yellow eyes or skin

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common
Blurred or double vision or any change in vision
dizziness or lightheadedness
Less common or rare
Abdominal or stomach cramps or pain
clumsiness or unsteadiness
excitement, nervousness, restlessness, or irritability
flushing or redness of face
muscle weakness
nausea or vomiting
pain or peeling of skin at place of injection (methocarbamol only)
trouble in sleeping
uncontrolled movements of eyes (methocarbamol injection only)

Although not all of the side effects listed above have been reported for all of these medicines, they have been reported for at least one of them. However, since all of these skeletal muscle relaxants have similar effects, it is possible that any of the above side effects may occur with any of these medicines.

In addition to the other side effects listed above, chlorzoxazone may cause your urine to turn orange or reddish purple. Methocarbamol may cause your urine to turn black, brown, or green. This effect is harmless and will go away when you stop taking the medicine. However, if you have any questions about this, check with your doctor.

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Last Updated: 6/12/2013
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