Muscle relaxants

Definition

   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.

Purpose

   Strains, sprains, and other muscle injuries can result in pain, stiffness, and muscle spasms. Muscle relaxants do not heal the injuries, but they do help ease the discomfort and stop muscle spasms.

Description

   Muscle relaxants work by acting on the central nervous system. In the United States, they are available only with a physician's prescription. Some muscle relaxants are available in Canada without a prescription. Most come only in tablet form. However, methocarbamol (Robaxin) is available in both tablet and injectable forms. Examples of muscle relaxants are carisoprodol (Soma), chlorzoxazone (Parafon Forte DSC), cyclobenzaprine (Flexeril), and methocarbamol (Robaxin).

Recommended dosage

   The dose of these medicines will be different for different patients. Check with the physician who prescribed the drug or the pharmacist who filled the prescription for the correct dosage. Always take muscle relaxants exactly as directed by your physician. Never take larger or more frequent doses, and do not take the drug for longer than directed.

Precautions

   Muscle relaxants are usually prescribed along with rest, exercise, physical therapy, or other treatments. Although the drugs may provide relief, they should never be considered a substitute for these other forms of treatment. The drugs may make the injury feel so much better that one is tempted to go back to normal activity, but doing too much too soon can actually make the injury worse.
These drugs work quite well for relieving muscle pain due to injuries, but are not effective for other types of pain. They should not be used for any other purpose other than for what they were prescribed.

   Some people feel drowsy, dizzy, confused, lightheaded, or less alert when using these drugs. The drugs may also cause blurred vision, clumsiness, or unsteadiness. For these reasons, anyone who takes these drugs should not drive, operate machinery, or do anything else that might be dangerous until they have found out how the drugs affect them.

   Because muscle relaxants work on the central nervous system, they may add to the effects of alcohol and other drugs that slow down the central nervous system, such as antihistamines, cold medicine, allergy medicine, sleep aids, medicine for seizures, tranquilizers, some pain relievers, and other muscle relaxants. They may also add to the effects of anesthetics, including those used for dental procedures. Anyone taking muscle relaxants should check with his or her physician before taking any of the above.

   Persons with diabetes should be aware that the metaxalone (Skelaxin) may cause false test results on one type of test for sugar in the urine.

Allergies

Breastfeeding

Side effects

   The most common side effects are vision changes, such as double vision or blurred vision; dizziness; lightheadedness; drowsiness; and dry mouth. These problems usually go away as the body adjusts to the drug and do not require medical treatment. If dry mouth is bothersome, suck on sugarless hard candy or ice chips, chew sugarless gum, or use saliva substitutes, which come in liquid and tablet forms. Less common side effects, such as stomach cramps or pain, nausea and vomiting, constipation, diarrhea, hiccups, clumsiness or unsteadiness, confusion, nervousness, restlessness, irritability, flushed or red face, headache, heartburn, weakness, trembling, and sleep problems, also may occur and do not need medical attention unless they do not go away or they interfere with normal activities.

   Methocarbamol and chlorzoxazone may cause harmless color changes in urine --orange or reddish-purple with chlorzoxazone and purple, brown, or green with methocarbamol. The urine will return to its normal color when the patient stops taking the medicine.

   More serious side effects are not common, but may occur. If any of the following side effects occur, check with the physician who prescribed the medicine as soon as possible:

• Breathing problems
  
• Swelling of the face
  
• Fainting
  
• Unusually fast or unusually slow heartbeat
  
• Fever
  
• Tightness in the chest
  
• Rash, itching, hives, or redness
  
• Burning, stinging, red, or bloodshot eyes
  
• Stuffy nose
  
• Unusual thoughts or dreams.
  

   The muscle relaxant chlorzoxazone (Parafon Forte DSC) has caused serious, life-threatening liver problems in some people. The reaction is rare, but anyone taking the drug should stop taking it and notify his or her physician immediately if any of these symptoms occur:

• Fever
  
• Rash
  
• Loss of appetite
  
• Nausea
  
• Vomiting
  
• Fatigue
  
• Pain in the upper right part of the abdomen
  
• Dark urine
  
• Yellow skin or eyes.
  

   Additional, rare side effects may occur with any muscle relaxants. Anyone who has unusual symptoms after taking these drugs should get in touch with his or her physician.