Chlorzoxazone: uses, appearance and warnings

Chlorzoxazone tablets are indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions. The mode of action of this drug has not been clearly identified, but may be related to its sedative properties. Chlorzoxazone does not directly relax tense skeletal muscles in man.

Chlorzoxazone tablets USP are supplied as follows: Chlorzoxazone tablets USP 375 mg are a white capsule shaped tablet, debossed “PAR” on the one side and “375” on another side. Free of physical defects. Bottles of 100 tablets NDC 0254-2053-01 Chlorzoxazone tablets USP 750 mg are a white capsule shaped tablet, debossed “PAR” on the trisected side (functional scoring) and “750” on the bisected side (functional scoring). Bottles of 100 tablets NDC 0254-2005-01 Dispense in tight container as defined in the official compendium. Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature]. To report SUSPECTED ADVERSE REACTIONS, contact Par Health at 1-800-828-9393 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. Manufactured for: Par Health USA Woodcliff Lake, NJ 07677 U.S.A. Product of Taiwan Made in India Neutral Code: TN/DRUGS/TN00002121 © 2026 Par Health, Inc. or one of its affiliates. OS2053-01-74-04 Revised: 07/2026

Chlorzoxazone tablets are contraindicated in patients with known intolerance to the drug.

Serious (including fatal) hepatocellular toxicity has been reported rarely in patients receiving chlorzoxazone. The mechanism is unknown but appears to be idiosyncratic and unpredictable. Factors predisposing patients to this rare event are not known. Patients should be instructed to report early signs and/or symptoms of hepatotoxicity such as fever, rash, anorexia, nausea, vomiting, fatigue, right upper quadrant pain, dark urine, or jaundice. Chlorzoxazone should be discontinued immediately and a physician consulted if any of these signs or symptoms develop. Chlorzoxazone use should also be discontinued if a patient develops abnormal liver enzymes (e.g., AST, ALT, alkaline phosphatase and bilirubin). The concomitant use of alcohol or other central nervous system depressants may have an additive effect. Usage in Pregnancy: The safe use of chlorzoxazone tablets has not been established with respect to the possible adverse effects upon fetal development. Therefore, it should be used in women of childbearing potential only when, in the judgment of the physician, the potential benefits outweigh the possible risks.

Chlorzoxazone containing products are usually well tolerated. It is possible in rare instances that chlorzoxazone may have been associated with gastrointestinal bleeding. Drowsiness, dizziness, light-headedness, malaise, or overstimulation may be noted by an occasional patient. Rarely, allergic-type skin rashes, petechiae, or ecchymoses may develop during treatment. Angioneurotic edema or anaphylactic reactions are extremely rare. There is no evidence that the drug will cause renal damage. Rarely, a patient may note discoloration of the urine resulting from a phenolic metabolite of chlorzoxazone. This finding is of no known clinical significance.