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| Clinical data | |
|---|---|
| Trade names | Lorzone, Paraflex, Muscol |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a682577 |
| License data | |
| Routes of administration | By mouth |
| Drug class | Skeletal muscle relaxants |
| ATC code | |
| Legal status | |
| Legal status | |
| Pharmacokinetic data | |
| Bioavailability | Well absorbed |
| Protein binding | 13–18% |
| Metabolism | Hepatic |
| Elimination half-life | 1.1 hours |
| Duration of action | 3–4 hours |
| Excretion | urine (<1%) |
| Identifiers | |
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| CAS Number | |
| PubChem CID | |
| IUPHAR/BPS | |
| DrugBank | |
| ChemSpider | |
| UNII | |
| KEGG | |
| ChEBI | |
| ChEMBL | |
| 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 acting muscle relaxant used to treat muscle spasm 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 names Lorzone, Paraflex and Muscol and in combination form as Parafon Forte, a combination of chlorzoxazone and acetaminophen (paracetamol). Possible side effects include dizziness, lightheadedness, malaise, nausea, vomiting.[medical citation needed] In rare cases, chlorzoxazone may cause severe liver dysfunction.[3] On the other hand, chlorzoxazone may reduce the liver toxicity of acetaminophen by competitive inhibition.[4]
It is available as a generic medication.[5]
Like metaxalone, its mechanism of action is still in question. It is believed that metaxalone works by altering serotonin 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] General central nervous system depression 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.
- ^ "Parafon DSC- chlorzoxazone tablet". DailyMed. 9 February 2010. Retrieved 5 November 2020.
- ^ "Lorzone- chlorzoxazone tablet". DailyMed. 21 June 2019. Retrieved 5 November 2020.
- ^ "Chlorzoxazone". LiverTox. National Institute of Diabetes and Digestive and Kidney Diseases. 2017-01-30. PMID 31643467. Retrieved 2024-05-10.
- ^ Pingili RB, Vemulapalli S, Gadamsetty MV, Presingu D, Katuri R, Rachamsetty V, et al. (2023-04-17). "Chlorzoxazone reduced the paracetamol-induced toxicity via competitive inhibition of CYP2E1-mediated metabolism". Future Journal of Pharmaceutical Sciences. 9 (1). doi:10.1186/s43094-023-00484-2. ISSN 2314-7253.
- ^ "Competitive Generic Therapy Approvals". U.S. Food and Drug Administration (FDA). 29 June 2023. Archived from the original on 29 June 2023. Retrieved 29 June 2023.