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| Clinical data | |
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| Trade names | Lorzone, Paraflex, Muscol |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a682577 |
| License data | |
| Routes of administration | By mouth |
| Drug class | Skeletal muscle relaxants |
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| Pharmacokinetic data | |
| Bioavailability | Well absorbed |
| Protein binding | 13–18% |
| Metabolism | Hepatic |
| Eliminationhalf-life | 1.1 hours |
| Duration of action | 3–4 hours |
| Excretion | urine (<1%) |
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| CompTox Dashboard(EPA) | |
| ECHA InfoCard | 100.002.186 |
| Chemical and physical data | |
| Formula | C7H4ClNO2 |
| Molar mass | 169.56 g·mol−1 |
| 3D model (JSmol) | |
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Chlorzoxazone (INN) is a centrally actingmuscle relaxant used to treat musclespasm and the resulting pain or discomfort. It can also be administered for acute pain in general and for tension headache (muscle contraction headache). It acts on the spinal cord by depressing reflexes. It is sold under the brand namesLorzone,Paraflex andMuscol and in combination form asParafon Forte, a combination of chlorzoxazone andacetaminophen (paracetamol). Possible side effects includedizziness,lightheadedness,malaise,nausea,vomiting.[medical citation needed] In rare cases, chlorzoxazone may cause severe liver dysfunction.[3] Conversely, chlorzoxazone may reduce the liver toxicity ofacetaminophen bycompetitive inhibition.[4]
It is available as ageneric medication.[5]
Likemetaxalone, its mechanism of action is still in question. It is believed that metaxalone works by alteringserotonin levels and acting as a mild MAO inhibitor.[medical citation needed] The mechanism of action of chlorzoxazone is thought[by whom?] to act on GABAA and GABAB receptors and voltage-gated calcium channels to a degree.[medical citation needed] Generalcentral nervous systemdepression is the only currently accepted aspect to its medical benefits.[medical citation needed] Elucidation of the exact mechanism of action is ongoing but there is limited study due to the existence of more effective, safe muscle relaxants (e.g.,diazepam,cyclobenzaprine,tizanidine), greatly limiting the potential benefit of identifying novel compounds which share chlorzoxazone's mechanism of action.
