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MUSCULO-SKELETAL SYSTEM › MUSCLE RELAXANTS › MUSCLE RELAXANTS, CENTRALLY ACTING AGENTS › Oxazol, thiazine, and triazine derivatives
chlorzoxazone
M03BB03
Forms & Strengths
- Tablet: 250 mg
- Tablet: 375 mg
- Tablet: 500 mg
- Caplet: 500 mg
Adult Dosing
- 250 mg to 500 mg orally 3 to 4 times daily
- Maximum dose: 750 mg 4 times daily (3000 mg/day)
Pediatric Dosing
- Safety and efficacy not established in pediatric patients under 18 years of age
Indications
- Adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions
Mechanism of Action
- Centrally acting skeletal muscle relaxant
- Acts primarily at the level of the spinal cord and subcortical areas of the brain to inhibit multisynaptic reflex arcs involved in producing and maintaining skeletal muscle spasm
Contraindications
- Known hypersensitivity to chlorzoxazone
- Impaired hepatic function or active liver disease
Adverse Reactions
- Drowsiness, dizziness, lightheadedness, malaise
- Nausea, vomiting, heartburn, abdominal pain
- Hepatotoxicity (drug-induced hepatitis, sometimes severe)
- Hypersensitivity reactions (rash, petechiae, ecchymoses, angioedema)
- Urine discoloration (red, purple, or orange-red due to a phenolic metabolite)
Drug Interactions
- Central nervous system (CNS) depressants (alcohol, opioids, sedatives, hypnotics): enhanced CNS depression and psychomotor impairment
- Inhibitors or inducers of hepatic cytochrome P450 enzymes may alter chlorzoxazone metabolism
- Hepatotoxic drugs: potential increased risk of cumulative liver toxicity
Curated Content: Needs Vetting Before Put to Clinical Use