Table of contents

  • Brand Names
  • Drug Combinations
  • Chemistry
  • Pharmacologic Category
  • Mechanism of Action
  • Therapeutic Use
  • Pregnancy and Lactation Implications
  • Contraindications
  • Warnings and Precautions
  • Adverse Reactions
  • Toxicological Effects
  • Caution and personalized dose adjustment in patients with the following genotypes
  • Other genes that may be involved
  • Substrate of
  • Inhibits
  • Drug Interactions
  • Nutrition/Nutraceutical Interactions
  • Dosage
  • Pharmacokinetics and Pharmacodynamics
  • Special Considerations

Brand Names


Denmark: Klorzoxazon; Hungary: Myoflexin; Romania: Clorzoxazon, Clorzoxazona; Sweden: Paraflex.

North America

USA: Chlorzoxazone, Parafon Forte.


Japan: Framenco, Slaxin.

Drug combinations

Chlorzoxazone and Acetaminophen

Chlorzoxazone and Ibuprofen

Chlorzoxazone, Acetaminophen, and Dexamethasone


Chlorzoxazone: C~7~H~4~ClNO~2~. Mw: 169.57. (1) 2(3H)-Benzoxazolone, 5-chloro-; (2) 5-Chloro-2-benzoxazolinone. CAS-95-25-0.

Pharmacologic Category

Centrally Acting Skeletal Muscle Relaxants. (ATC-Code: M03BB03).

Mechanism of action

CNS depressant with sedative and skeletal muscle relaxant effects. Inhibits multisynaptic reflex arcs at the level of the spinal cord and subcortical areas of the brain, resulting in reduction of skeletal muscle spasm with relief of pain and increased mobility of involved muscles.

Therapeutic use

Muscle spasm and pain associated with acute musculoskeletal conditions.

Pregnancy and lactiation implications

Safe use of chlorzoxazone during pregnancy not established. Should not be used in women who are or may become pregnant unless potential benefits outweigh possible risks. Use not recommended during lactation.

Unlabeled use


Hypersensitivity to chlorzoxazone or any component of the formulation. Impaired liver function.

Warnings and precautions

Serious, possibly fatal, hepatotoxicity reported rarely. Performance of activities requiring mental alertness or physical coordination may be impaired. Sensitivity reactions (e.g. urticaria, redness, petechiae, pruritus) reported rarely. Angioedema and anaphylactic reactions are extremely rare. Caution in allergies or with history of allergic drug reactions.



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