|Pronunciation||klor zox' a zone|
|Trade names||Lorzone, Paraflex, Muscol, others|
|Drug class||Muscle relaxant|
|Main uses||Low back pain, muscle spasms|
|Side effects||Dizziness, sleepiness, headache, tremor|
|Onset of action||With 1 hr|
|Duration of action||Up to 4 hr|
|Elimination half-life||1.1 hr|
|Chemical and physical data|
|Molar mass||169.56 g·mol−1|
|3D model (JSmol)|
Chlorzoxazone, sold under the brand names Lorzone among others, is a muscle relaxant used to treat low back pain and muscle spasms. Benefits are moderate. It is not useful for neurological problems such as cerebral palsy. It is taken by mouth. Effects begin within an hour and last for up to 4 hours.
Common side effects include dizziness, sleepiness, headache, and tremor. Other side effects may include liver problems and angioedema. Safety in pregnancy is unclear. It works at the level of the spinal cord and brain.
Chlorzoxazone was approved for medical use in the United States in 1958. It is available as a generic medication. In the United States 60 pills of 500 mg costs about 18 USD as of 2022. As of 2017 it remains widely used.
The usual recommended dose in adults is 250 to 750 mg by mouth three to four times daily, reducing the dose to lowest effective level once a response occurs. It is typically given for 1 to 4 weeks only.
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