Muscle relaxants

Encyclopedia of Medicine, Apr 06, 2001 by Nancy Ross-Flanigan

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.

Muscle relaxants may interact with some other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. Anyone who plans to take muscle relaxants should let the physician know all other medicines he or she is taking. Among the drugs that may interact with muscle relaxants are:

• Central nervous system (CNS) depressants, such as antihistamines, tranquilizers, sedatives, sleep aids, some pain relievers, cold medicines, allergy medicines, and medicines for seizures.
• Tricyclic antidepressants, such as amitriptyline (Elavil), imipramine (Tofranil), and desipramine (Norpramin).
• Monoamine oxidase inhibitors (MAO), such as phenelzine (Nardil) or tranylcypromine (Parnate). Serious, life-threatening reactions are possible in patients who take the muscle relaxant cyclobenzaprine (Flexeril) within two weeks of taking MAO inhibitors.
• Antispasmodic drugs, such as belladonna alkaloids and phenobarbital (Donnatal) or dicyclomine (Bentyl)
• Barbiturates, such as phenobarbital
• High blood pressure drugs, that contain guanethidine such as Esimil or Ismelin.