Prescription Drugs Information
HEALTH GUIDE / Prescription Drugs / Muscle Relaxants

Muscle Relaxants

Skeletal Muscle Relaxants


About skeletal muscle relaxants

Skeletal muscle relaxants are drugs that work on the central nervous system to relax certain skeletal muscles in the body. Skeletal muscles are muscles that are attached to the bones and are associated with movement. Skeletal muscle relaxants are typically used to treat muscular pain and spasms due to musculoskeletal conditions, as well as spasticity resulting from syndromes of the upper motor neurons.

Physicians usually prescribe these medications early in a patient’s treatment regimen. In most cases, they are intended to be used on a short-term basis only. Long-term use of skeletal muscle relaxants involves the potential for abuse and dependency, and is therefore discouraged by many physicians.

Most skeletal muscle relaxants are taken in tablet form, but a prescription injection also is available for some patients. Examples of skeletal muscle relaxants include:

Generic NameBrand Name(s)


Kemstro, Lioresal




Parfon Forte DSC, Strifon Forte DSC


Amrix, Flexeril









quinine sulfate




Conditions treated

Skeletal muscle relaxants are often used to relieve tenderness and muscle spasms related to various types of musculoskeletal conditions. These conditions tend to be acute and are quite common. Such conditions include:

  • Fibromyalgia
  • Mechanical low-back or neck pain
  • Myofascial pain syndromes
  • Nocturnal leg cramps
  • Tension headaches

Skeletal muscle relaxants also may be used to treat neurological conditions associated with spasticity. This is a condition characterized by tight or stiff muscles and an inability to control those muscles. For many patients, spasticity can be disabling and painful. These conditions are chronic, but tend to be less common than musculoskeletal conditions. Neurological conditions that may be treated with skeletal muscle relaxants include:

  • Cerebral palsy
  • Multiple sclerosis
  • Muscle spasms following strokes
  • Spinal cord injuries
  • Traumatic brain injury

Conditions of concern with muscle relaxants

Certain medical conditions may increase the likelihood of experiencing side effects associated with skeletal muscle relaxants. Patients are urged to tell their physician if they have any allergies, especially if they have ever experienced an allergic reaction to any muscle relaxant or to other substances such as foods, preservatives or dyes.

Other conditions that should be disclosed to a physician include:

  • Blood disease resulting from allergies or reaction to medicine
  • Epilepsy
  • History of drug dependency
  • Kidney disease
  • Liver disease
  • Porphyria (disease that causes accumulation of chemicals called porphyrins or porphyrin precursors)

In addition, patients with diabetes may have false urine-sugar tests when taking the muscle relaxant metaxalone.

Side effects

Potential side effects of muscle relaxants

Skeletal muscle relaxants can cause various side effects. Some patients experience blurred vision, clumsiness or unsteadiness. Other side effects associated with muscle relaxants include:

  • Dizziness
  • Drowsiness
  • Fainting
  • Lack of alertness
  • Lightheadedness

Some side effects may be more serious, and include abdominal pain, breathing difficulties, blood in urine or stool, sore throat and fever. The skeletal muscle relaxant quinine sulfate has been associated with rare but potentially life-threatening heart problems. Patients who take these medications are advised to promptly report any significant side effects to a physician.

Because of the tendency for skeletal muscle relaxants to cause drowsiness, people are urged to avoid taking these drugs before certain activities (e.g., driving, using machinery) unless they know how they are likely to be affected.


Drug or other interactions

Patients should consult their physicians before taking any additional prescriptions, over-the-counter medications, nutritional supplements or herbal medications. Drugs that may interact poorly when taken with skeletal muscle relaxants include:

  • Alcohol
  • Central nervous system depressants (e.g., antihistamines, tranquilizers)
  • Tricyclic antidepressants

In general, skeletal muscular relaxants add to the effects of these drugs, which may cause more severe drowsiness and increase the risk of side effects.

How to use

Pregnancy use issues

Although formal studies involving pregnant women have not been conducted, skeletal muscle relaxants have not been shown to cause problems for pregnant women or their fetuses. Animal studies also have not indicated a link between skeletal muscle relaxants and birth defects. Nonetheless, women who are pregnant or who may become pregnant are advised to consult their physician before taking skeletal muscle relaxants.

Some muscle relaxants have been shown to pass into breast milk and cause symptoms such as drowsiness and upset stomach in nursing babies. As a result, women who are breastfeeding should not use these drugs without first obtaining a physician’s approval.

Child use issues

Studies have not been performed regarding the effect of skeletal muscle relaxants on children. Experts generally recommend that some of these medications not be used in children. Others may be safe and do not appear to cause side effects that are different in children than they are in adults. Parents are advised to consult a physician before allowing their child to use skeletal muscle relaxants.

Elderly use issues

Studies have not been performed regarding the effect of skeletal muscle relaxants on the elderly. As a result, experts are not sure if the medications are more or less effective in older adults than they are in younger adults, or if older adults have an increased risk of side effects from skeletal muscular relaxants.

However, some experts warn that skeletal muscle relaxants are more likely to cause some side effects in elderly patients, including blocking the action of the neurotransmitter acetylcholine in the body and causing sedation and weakness. Elderly people are advised not to use skeletal muscle relaxants without first consulting a physician.

Symptoms of medication overdose

Patients or the loved ones of patients exhibiting any of these symptoms should contact their physician immediately:

  • Absence of reflexes
  • Coma
  • Extreme drowsiness
  • Nausea and vomiting
  • Rash
  • Respiratory problems
  • Seizures
  • Prolonged or extreme visual disorders

Questions for your doctor on muscle relaxants

Patients may wish to ask their doctor the following questions related to skeletal muscle relaxants:
  1. Why do you suggest I take skeletal muscle relaxants to treat my condition?
  2. What are the alternative treatments available to me?
  3. Which skeletal muscle relaxant do you believe would be most effective for me?
  4. What are the side effects associated with this drug?
  5. Will I have to stop taking other medications while I am on this drug?
  6. How soon after I start taking this drug should I begin to notice improvement?
  7. How long will I be required to take this medication?
  8. What should I do if I miss a dose of my drug?
  9. If the drug is not effective, can I try another skeletal muscle relaxant?
  10. Is this drug safe for me if I’m pregnant or breastfeeding?
  11. Is this drug safe for my child/elderly parent?

©2007-2012. All rights reserved. This site is for information and support only.