Chlorzoxazone Side Effects

Medically reviewed by Drugs.com. Last updated on Nov 17, 2023.

Applies to chlorzoxazone: oral tablet.

Serious side effects of Chlorzoxazone

Along with its needed effects, chlorzoxazone 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 immediately if any of the following side effects occur while taking chlorzoxazone:

Rare

• Bloody or black, tarry stools
• clay-colored stools
• constipation
• cough
• dark urine
• decreased appetite
• difficulty swallowing
• dizziness
• fast heartbeat
• fever
• headache
• hives
• itching
• large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
• loss of appetite
• nausea and vomiting
• puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
• severe stomach pain
• shortness of breath
• skin rash
• swelling of the feet or lower legs
• tightness in the chest
• unusual tiredness or weakness
• vomiting of blood or material that looks like coffee grounds
• wheezing
• yellow eyes or skin

Get emergency help immediately if any of the following symptoms of overdose occur while taking chlorzoxazone:

Symptoms of overdose

• Diarrhea
• difficult or troubled breathing
• drowsiness
• general feeling of discomfort or illness
• headache
• irregular, fast or slow, or shallow breathing
• lightheadedness
• nausea
• pale or blue lips, fingernails, or skin
• sluggishness
• vomiting

Other side effects of Chlorzoxazone

Some side effects of chlorzoxazone 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:

Rare

• Bruising
• large, flat, blue, or purplish patches in the skin
• small red or purple spots on the skin

For Healthcare Professionals

Applies to chlorzoxazone: compounding powder, oral tablet.

General

Adverse reactions such as gastrointestinal disturbances, drowsiness, dizziness, or lightheadedness may occur.^[Ref]

Gastrointestinal

Frequency not reported: Gastrointestinal disturbances, gastrointestinal bleeding^[Ref]

Hypersensitivity

Rarely skin hypersensitivity type reactions such as skin rashes, petechiae, and ecchymosis have develop; extremely rare reports of angioneurotic edema and anaphylactic reactions have been received.^[Ref]

Frequency not reported: Allergic-type skin rashes, petechiae, ecchymosis, angioneurotic edema, anaphylactic reactions^[Ref]

Nervous system

Frequency not reported: Drowsiness, dizziness, light-headedness, malaise, and overstimulation.^[Ref]

Genitourinary

Urine discoloration attributed to a phenolic metabolite have been reported; the clinical significance of this is unknown.

Rare (less than 0.1%): Urine discoloration

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

Medical Disclaimer