Skeletal Muscle Relaxants (Systemic)

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

Fainting; fast heartbeat; fever; 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

Rare

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

Other 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. However, check with your doctor if any of the following side effects continue or are bothersome:

More common

Blurred or double vision or any change in vision; dizziness or lightheadedness; drowsiness

Less common or rare

Abdominal or stomach cramps or pain; clumsiness or unsteadiness; confusion; constipation; diarrhea; excitement, nervousness, restlessness, or irritability; flushing or redness of face; headache; heartburn; hiccups; muscle weakness; nausea or vomiting; pain or peeling of skin at place of injection (methocarbamol only); trembling; 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 above may also occur in some patients. If you notice any other effects, check with your doctor.